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| Data Sheet AS3910 13.56 MHz RFID Reader IC, ISO-14443 A/B 1 General Description The AS3910 is a high performance 13.56MHz HF RFID Reader IC. With austriamicrosystems' unique antenna management technology it is optimized for applications with directly driven antennas. The AS3910 is unequalled in the domain of HF Reader ICs in that it contains two differential low impedance (1.5) antenna drivers. These drivers are unmatched meaning the IC can deliver up to 8 times the output power of a standard HF Reader IC using the same power supply voltage. Additionally using this configuration means half of the power consumption at the same output power. The IC has an operating voltage down to 2.4V and a low power operating mode of 5mA. This means the AS3910 is ideal for portable or battery powered applications. For applications where high power is required (EMV) the AS3910 can attain up to 1W. This means there is no need for complex external booster circuitry. The component count and complexity of the design is further reduced through the patented automatic modulation depth adjustment. The analog front end (AFE) is complimented by a highly integrated data framing engine for both ISO-14443 A and B. This includes data rates up to 848kbits with all framing and synchronization tasks on board. This enables the customer to build a complete HF RFID Reader using only a low end micro. The AS3910 not only supports reader to tag communication, but sports Peer to Peer communication using the NFCIP-1 active communication mode with a data rate of 106kbps. The IC has a SPI, which enables bi-directional communication with the external microcontroller. Other standard and custom protocols, such as ISO-15693 can be implemented via transparent mode. 2 Key Features Close loop adjustment of ASK modulation for accurate control of modulation depth in case of ISO-14443B protocol Antenna trimming system providing correction range of LC Low power operating mode reduces receiver consumption from 10mA to 5mA Low power (3.5A) NFC target mode Integrated regulators to boost system PSRR AM/PM demodulator to eliminate communication holes RSSI measurement Accurate RF envelope measurement (8 bit A/D) High output power at 3.3V power supply: - up to 1W in case regulator is externally shorted - up to 500mW in case differential output and antenna trimming is used - up to 125mW in case of single ended output and antenna trimming is used Squelch feature which performs gain reduction to compensate for noise generated by transponder processing User selectable and automatic gain control Transparent mode to implement other standard and custom protocols (ISO-15693, Felica, ....) Quartz oscillator capable of operating with 13.56MHz or 27.12MHz crystal with fast start-up Additional A/D converter input, Serial peripheral interface (SPI) with 32 byte FIFO Supply voltage range from 2.4V to 3.6V Wide temperature range: -40C to 85C QFN 32 5x5 package 3 Applications The AS3910 is ideal for applications where the reader antenna is directly driven (no 50 cable). It also includes several unique features, which make it especially suitable for low power and battery powered applications. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 1 - 47 AS3910 Data Sheet - A p p l i c a t i o n s Figure 1. AS3910 HF RFID Reader IC Block Diagram XTO XTI Oscillator Regulators Bias Logic FIFO FIFO Transmitter RFO1 RFO2 Control Logic SPI SPI Interface A/D Converter Phase & Amplitude Detector Framing Receiver RFI1 RFI2 External Field Detector AS3910 HF RFID Reader IC Block Diagram www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 2 - 47 AS3910 Data Sheet - C o n t e n t s Contents 1 General Description 2 Key Features 3 Applications .................................................................................................................................................................. 1 ............................................................................................................................................................................ 1 .............................................................................................................................................................................. 1 ....................................................................................................................................................................... 5 ................................................................................................................................................................................... 5 4 Pin Assignments 4.1 Pin Descriptions 5 Absolute Maximum Ratings 6 Electrical Characteristics 7 Detailed Description ...................................................................................................................................................... 7 .......................................................................................................................................................... 8 ............................................................................................................................................................... 10 7.0.1 Transmitter ................................................................................................................................................................................. 11 7.0.2 Receiver ..................................................................................................................................................................................... 11 7.0.3 Phase and Amplitude Detector .................................................................................................................................................. 11 7.0.4 A/D Converter ............................................................................................................................................................................ 11 7.0.5 External Field Detector .............................................................................................................................................................. 11 7.0.6 Quartz Crystal Oscillator ............................................................................................................................................................ 11 7.0.7 Power Supply Regulators .......................................................................................................................................................... 11 7.0.8 POR and Bias ............................................................................................................................................................................ 11 7.0.9 ISO-14443 and NFCIP Framing ................................................................................................................................................ 12 7.0.10 FIFO ......................................................................................................................................................................................... 12 7.0.11 Control Logic ............................................................................................................................................................................ 12 7.0.12 SPI Interface ............................................................................................................................................................................ 12 8 Application Information 8.1 Operating Modes 8.2 Transmitter 8.3 Receiver ........................................................................................................................................................... 13 ................................................................................................................................................................................ 13 ......................................................................................................................................................................................... 13 ............................................................................................................................................................................................. 13 8.3.1 Gain Reduction, AGC and Squelch ........................................................................................................................................... 14 8.3.2 RSSI .......................................................................................................................................................................................... 14 8.3.3 AM and PM Demodulation ......................................................................................................................................................... 14 8.4 A/D Converter .................................................................................................................................................................................... 14 .......................................................................................................................................................... 15 8.5 Phase and Amplitude Detector 8.5.1 Phase Detector .......................................................................................................................................................................... 15 8.5.2 Amplitude Detector .................................................................................................................................................................... 15 8.6 External Field Detector ....................................................................................................................................................................... 15 8.6.1 Target Activation Detector ......................................................................................................................................................... 15 8.6.2 RF Collision Avoidance Detector ............................................................................................................................................... 15 8.7 Quartz Crystal Oscillator 8.8 Power Supply, Regulators 8.9.1 8.9.2 8.9.3 8.9.4 8.9.5 8.9.6 8.9.7 8.9.8 .................................................................................................................................................................... 15 .................................................................................................................................................................. 16 ....................................................................................................................................... 16 8.9 Communication to External Microcontroller Serial Peripheral Interface (SPI) ................................................................................................................................................ 17 SPI Operation MODE Bits ......................................................................................................................................................... 17 Writing of Data to Addressable Registers (WRITE Mode) ......................................................................................................... 17 Reading of Data from Addressable Registers (READ Mode) .................................................................................................... 18 Sending Direct Commands ........................................................................................................................................................ 19 Loading Transmitting Data into FIFO ......................................................................................................................................... 19 Reading Received Data from FIFO ........................................................................................................................................... 19 Interrupt Interface ...................................................................................................................................................................... 19 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 3 - 47 AS3910 Data Sheet - C o n t e n t s 8.9.9 FIFO Water Level and FIFO Status Register ............................................................................................................................. 20 8.10 Direct Commands ............................................................................................................................................................................ 20 8.10.1 Set Default ............................................................................................................................................................................... 21 8.10.2 Clear ........................................................................................................................................................................................ 21 8.10.3 Transmit Commands ............................................................................................................................................................... 21 8.10.4 NFC Transmit Commands ....................................................................................................................................................... 21 8.10.5 Mask Receive Data and Unmask Receive Data ...................................................................................................................... 22 8.10.6 AD Convert .............................................................................................................................................................................. 22 8.10.7 Measure RF ............................................................................................................................................................................. 22 8.10.8 Squelch .................................................................................................................................................................................... 22 8.10.9 Clear Squelch .......................................................................................................................................................................... 22 8.10.10 Adjust Regulators .................................................................................................................................................................. 22 8.10.11 Calibrate Modulation Depth ................................................................................................................................................... 23 8.10.12 Calibrate Antenna .................................................................................................................................................................. 23 8.10.13 Check Antenna Resonance ................................................................................................................................................... 23 8.10.14 Clear RSSI ............................................................................................................................................................................. 23 8.10.15 Transparent Mode ................................................................................................................................................................. 23 8.11 Registers 8.11.1 8.11.2 8.11.3 8.11.4 8.11.5 8.11.6 8.11.7 8.11.8 .......................................................................................................................................................................................... 23 Main Registers ......................................................................................................................................................................... 24 Configuration Registers ........................................................................................................................................................... 25 Interrupt Register and Associated Registers ........................................................................................................................... 28 A/D Converter Output Register ................................................................................................................................................ 30 Antenna Calibration Registers ................................................................................................................................................. 31 AM Modulation Depth and Antenna Driver Registers .............................................................................................................. 32 NFCIP Field Detection Threshold Register .............................................................................................................................. 33 Regulator Registers ................................................................................................................................................................. 35 ............................................................................................................................................................ 37 8.12 Typical Operating Sequence 8.12.1 ISO-14443 Reader Operation .................................................................................................................................................. 37 8.12.2 NFCIP-1 Operation .................................................................................................................................................................. 37 8.13 ISO-14443A SELECT SEQUENCE 8.13.1 8.13.2 8.13.3 8.13.4 ................................................................................................................................................. 38 REQA and WUPA .................................................................................................................................................................... 38 ANTICOLLISION ..................................................................................................................................................................... 39 Collision Detection ................................................................................................................................................................... 39 SELECT ................................................................................................................................................................................... 39 ............................................................................................................................................... 40 ............................................................................................................................ 40 8.14 Receiving 4Bit Tag Response Frame 8.15 AM Modulation Depth: Definition and Calibration 8.15.1 AM Modulation Depth Definition Using Direct Command Calibrate Modulation Depth ........................................................... 40 8.15.2 AM Modulation Depth Definition Using Antenna Driver AM Modulated Level Definition Register (#12) ................................. 41 8.16 Antenna LC Tank Resonance: Checking and Calibration ................................................................................................................ 41 8.16.1 Check Antenna Resonance ..................................................................................................................................................... 42 8.16.2 Calibrate Antenna Resonance ................................................................................................................................................. 42 8.17 Transparent Mode ............................................................................................................................................................................ 43 .......................................................................................................................... 44 ......................................................... 44 8.18 Active Receive - Use in ISO-14443B Anticollision 8.20 Test Pins 8.19 ISO-14443B, Reduction of TR0 and TR1 and Suppression of EOF/SOF in PICC Response ........................................................................................................................................................................................... 44 9 Package Drawings and Markings 10 Ordering Information ........................................................................................................................................... 45 ............................................................................................................................................................. 47 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 4 - 47 AS3910 Data Sheet - P i n A s s i g n m e n t s 4 Pin Assignments Figure 2. Pin Assignments (Top View) MCU_CLK SDATAO SDATAI VSN_A 26 32 TIO EN TEST XTO XTI VSN_D VSP_A VDD 1 2 3 4 5 6 7 8 9 VSP_RF 31 30 29 28 27 25 24 23 22 AGD RFI2 RFI1 VSS TRIM2_0 TRIM1_0 TRIM2_1 TRIM1_1 AD_IN 21 20 19 18 17 16 TRIM2_2 SCLK AS3910 10 RFO1 11 RFO2 12 VSN_RF 13 TRIM1_3 INTR 14 TRIM2_3 SEN 15 TRIM1_2 4.1 Pin Descriptions Table 1. Pin Descriptions Pin Name TIO EN TEST XTO XTI VSN_D VSP_A VDD VSP_RF RFO1 RFO2 VSN_RF TRIM1_3 Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 Pin Type Digital bidirectional Digital input with pull-down Digital input with pull-down Analog output Analog input Supply Analog I/O Supply Analog I/O Analog output Analog output Supply Analog input Test IO pin Enable input Test input Xtal oscillator output Xtal oscillator input Digital ground Analog supply, regulator output External positive supply Supply, regulator output for antenna drivers Antenna driver output Antenna driver output Ground of antenna drivers Input to trim antenna resonant circuit Description www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 5 - 47 AS3910 Data Sheet - P i n A s s i g n m e n t s Table 1. Pin Descriptions Pin Name TRIM2_3 TRIM1_2 TRIM2_2 TRIM1_1 TRIM2_1 TRIM1_0 TRIM2_0 VSS RFI1 RFI2 AGD AD_IN VSN_A INTR MCU_CLK SDATAO SDATAI SCLK SEN VSUB Pin Number 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 exposed pad Pin Type Analog input Analog input Analog input Analog input Analog input Analog input Analog input Supply pad Analog input Analog input Analog Input / Output Analog input Supply pad Digital output Digital output Digital Output / Tristate Digital input Digital input Digital input Supply Description Input to trim antenna resonant circuit Input to trim antenna resonant circuit Input to trim antenna resonant circuit Input to trim antenna resonant circuit Input to trim antenna resonant circuit Input to trim antenna resonant circuit Input to trim antenna resonant circuit Ground, die substrate potential Receiver input Receiver input Analog reference voltage A/D converter input Analog ground Interrupt request output Micro Controller Clock Output Serial Peripheral Interface DATA output Serial Peripheral Interface DATA input Serial Peripheral Interface Clock Serial Peripheral Interface Enable Die substrate potential, to be connected to VSS on PCB www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 6 - 47 AS3910 Data Sheet - A b s o l u t e M a x i m u m R a t i n g s 5 Absolute Maximum Ratings Stresses beyond those listed in Table 2 may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Electrical Characteristics on page 8 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings Parameter DC supply voltage (VDD) Input pin voltage (all except TRIM pins), (VIN) Input pin voltage TRIM pins, (VINTRIM) Input current (latchup immunity), (ISCR) ESD Total power dissipation (all supplies and outputs), (Pt) Storage temperature, (Tstrg) -55 Min -0.5 -0.5 -0.5 -100 2 Package body temperature, (Tbody) 260 C Humidity non-condensing 5 85 % www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 7 - 47 AS3910 Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6 Electrical Characteristics Table 3. Operating Conditions Symbol VDD VSS TAMB Parameter Positive supply voltage Negative supply voltage Ambient Temperature Input pin voltage TRIM pins Table 4. DC / AC Characteristics For Digital Inputs and Outputs Symbol Parameter Conditions Min Typ Max Units CMOS Inputs Valid for input pins EN, SEN, SDATAI, SCLK and TEST VIH VIL ILEAK RPD High level input voltage Low level input voltage Input leakage current Pull-down resistance pad EN 100 0.7 * VDD 0.3 * VDD 2 V V A k Conditions In case power supply is lower than 2.6V, PSSR can not be improved using internal regulators (minimum regulated voltage is 2.4V) Min 2.4 0 -40 Typ Max 3.6 0 85 30 Units V V C V CMOS Outputs Valid for output pins SDATAO, INTR and MCU_CLK VOH VOL CL RO SPI Timing TSENL TSCLKL TSCLKH TSENCLKR TSENCLKF SPI reset (SEN low) SCLK low SCLK high SEN rising to SCLK rising SCLK falling to SEN falling first SCLK pulse last SCLK pulse 100 100 100 50 50 ns ns ns ns ns High level output voltage Low level output voltage Capacitive load Output Resistance 250 ISOURCE = 1mA ISINK = 1mA 0.9 * VDD 0.1 * VDD 50 500 V V pF www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 8 - 47 AS3910 Data Sheet - E l e c t r i c a l C h a r a c t e r i s t i c s VDD = 3.3V, Temperature = 25C, unless otherwise noted. Table 5. Electrical Characteristics Symbol IPD Parameter Supply current in Power-down mode Supply current in Initial NFC target mode IRD IRA ILP RRFO VRFI VRFI_LP RRFI VPOR VAGD VAR TOSU Supply current in Ready mode Supply current Receiver active Supply current all active, low power receiver mode RFO1 and RFO2 driver output resistance RFI input sensitivity RFI input sensitivity, low power receiver mode RFI input resistance Power on Reset Voltage AGD voltage Regulator drop Oscillator start-up time After execution of direct command Adjust Regulators 13.56MHz or 27.12MHz crystal RS=50 max, load capacitance according to crystal specification 1.0 1.4 13.56 MHz Xtal used, MCU_CLK disabled 13.56 MHz Xtal used, MCU_CLK disabled IRFO=10mA All segments ON fSUB=848kHz 1 Conditions Min Typ 0.3 3.5 2 5 3 1.5 0.5 1.5 10 1.4 1.5 250 0.7 Max 2 7 3 7 5 4 Units A A mA mA mA mVrms mVrms k fSUB=848kHz <2.4 1.6 V V mV ms 1. Amplitude of carrier signal at RFI inputs is 2.5Vpp, maximum amplitude is 3Vpp. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 9 - 47 AS3910 Data Sheet - D e t a i l e d D e s c r i p t i o n 7 Detailed Description Figure 3. Minimum Configuration with Single Sided Antenna Driving +3.3V C EN SEN SDATAO SDATAI SCLK INTR MCU_CLK TEST XTI XTO TRIM1_x TRIM2_x VDD AGD VSS VSP_A VSN_A VSN_D AS3910 +3.3V VDD VSP_RF VSN_RF RF01 RF02 RFI1 RFI2 Antenna Figure 4. Minimum Configuration with Differential Antenna Driving C EN SEN SDATAO SDATAI SCLK INTR MCU_CLK TEST XTI XTO TRIM1_x TRIM2_x AGD VSS VSP_A VSN_A VSN_D AS3910 VSP_RF VSN_RF RF01 RF02 RFI1 RFI2 1/2 Antenna 1/2 Antenna www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 10 - 47 AS3910 Data Sheet - D e t a i l e d D e s c r i p t i o n 7.0.1 Transmitter The Transmitter incorporates drivers, which drive external antenna through pads RFO1 and RFO2. Single sided and differential driving is possible. The transmitter block additionally contains a subblock, which modulates transmitted signal for communication reader to transponder (OOK or configurable AM modulation). The AS3910 transmitter is indented to directly drive antennas (without 50 cable, usually antenna is on the same PCB). Operation with 50 cable is also possible, but in that case some of the advanced features are not possible. 7.0.2 Receiver The receiver detects transponder modulation superimposed on the 13.56MHz carrier signal. The receiver chain is composed of a peak detector followed by two stages with gain and filtering function and a final digitizer stage. The filter characteristics are adjusted to optimize performance over different ISO modes and data rates (subcarrier frequencies from 212 kHz to 848 kHz are supported). The receiver chain input is the RFI1 pin; output of digitizer stage is demodulated subcarrier signal. Receiver also contains a subblock, which helps to detect the presence of external RF field in NFCIP target mode. The receiver chain incorporates several features, which enable reliable operation in challenging phase and noise conditions. 7.0.3 Phase and Amplitude Detector The phase detector observes the phase difference between the transmitter output signals (RFO1 and RFO2) and the pad signals RFI1 and RFI2. The pad signals RFI1 and RFI2 are proportional to the signal on the antenna LC tank. RFI1 and RFI2 signals are also used to run the self-mixer, which generates output proportional to their amplitude. The phase detector and self mixer blocks are used for several purposes: Variation of RFI1 and RFI2 phase is used to perform PM demodulation Average phase difference between RFOx pins and RFIx pins is used to check antenna tuning Output of mixer is used to measure amplitude of signal present on pins RFI1 and RFI2 7.0.4 A/D Converter The AS3910 contains a built-in A/D Converter. Its input can be multiplexed from different sources and is used in several applications (measurement of RF amplitude, calibration of modulation depth, checking of the antenna LC tank resonance, A/D conversion of signal applied to pin AD_IN). The result of A/D conversion is stored in a register, which can be read through the SPI interface. 7.0.5 External Field Detector The external field detector is a low power block, which is switched on in NFCIP target mode to detect the presence of initiator field. It is also used during the NFCIP Collision Avoidance procedure. 7.0.6 Quartz Crystal Oscillator The quartz crystal oscillator can operate with 13.56MHz and 27.12MHz crystals. At start-up the transconductance of the oscillator is increased to achieve fast start-up. Since the start-up time varies depending on crystal type, temperature and other parameters, the oscillator amplitude is observed and an interrupt is sent when stable operation is reached to inform the controller that the clock signal is stable and reader field can be switched on. It also provides a clock signal to the external microcontroller (MCU_CLK) according to setting in the control register. 7.0.7 Power Supply Regulators Integrated power supply regulators ensure high power supply rejection of a complete reader system. At power up, the regulators are transparent. In case PSRR of the reader system has to be improved, then the command Adjust Regulators is sent. As a result of this command, the power supply level of VDD is measured in maximum load conditions and the regulated voltage reference is set 250mV below this measured level to assure a stable regulated supply. The resulting regulated voltage is stored in a register. It is also possible to define regulated voltage by writing a configuration register. In order to decouple any noise sources from different parts of IC there are two regulators integrated with separated external blocking capacitors (regulated voltage of both is the same). One regulator is for the analog blocks, the other one is for the antenna drivers. Logic and digital I/O pads are supplied directly from VDD (negative supply pin for logic and digital I/O is separated to avoid coupling of logic induced noise in the substrate). This block additionally generates a reference voltage for the analog processing (AGD - analog ground). This voltage also has an associated external buffer capacitor. 7.0.8 POR and Bias This block contains the bias current and voltage generator, which provides bias currents and reference voltages to all other blocks. It also incorporates a Power on Reset (POR) circuit, which provides a reset at power-up and at low supply levels. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 11 - 47 AS3910 Data Sheet - D e t a i l e d D e s c r i p t i o n 7.0.9 ISO-14443 and NFCIP Framing This block performs ISO-14443 and NFCIP-1 106 kbps active communication framing for receive and transmit according to the selected ISO mode and data rate settings. In reception, it takes demodulated subcarrier signal from Receiver. It recognizes the SOF, EOF and data bits; performs parity and CRC check; organizes the received data in bytes and places them in the FIFO. During transmit, it operates inversely; it takes bytes from FIFO; generates parity and CRC bits; adds SOF and EOF; and performs final encoding before passing modulation signal to transmitter. In Transparent mode, the framing and FIFO are bypassed; the digitized subcarrier signal, which is Receiver output is directly sent to SDATAO pin; signal applied to SDATAI pin is directly used to modulate the transmitter. 7.0.10 FIFO The AS3910 contains a 32byte FIFO. Depending on the mode, it contains either data that has been received or data that is to be transmitted. 7.0.11 Control Logic The control logic contains I/O registers, which define the operation of device. 7.0.12 SPI Interface A 4-wire Serial Peripheral interface (SPI) is used for communication between external microcontroller and the AS3910. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 12 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8 Application Information 8.1 Operating Modes The AS3910 operating mode is defined by the content of the Operation Control Register (address #01). At power up, all bits of the Operation Control Register are set to 0 and the AS3910 is in Power-down mode. In this mode - the AFE static power consumption is minimized, only the POR and part of bias are active, regulators are transparent and are not operating. The SPI is still functional in this mode; so all settings of ISO mode definition and configuration registers can be done. Control bit en (bit 7 of Operation Control Register) is controlling both the oscillator and regulators. When this bit is set, the device enters in Ready mode. In this mode, the oscillator and regulators are enabled. An interrupt is sent to inform the microcontroller when the oscillator frequency is stable. Another possibility to enter in Ready mode is to assert EN pin high (logic OR function between bit en and pin EN). Enable of Receiver and Transmitter are separated, so it is possible to operate one without switching on the other (control bits rx_en and tx_en). In some cases this may be useful, in case the reader field has to be maintained and there is no transponder response expected receiver can be switched-off to save current. Another example is NFCIP target mode in which RF field is generated by the initiator and only Receiver operates. The receiver also has a low power mode in which its power consumption and as consequence sensitivity are reduced. This mode is entered in by setting control bit rx_lp. The last control bit of the Operation Control Register is nfc_t bit. Setting of this bit is only allowed in case the NFC mode is set in the ISO mode definition register. Setting this bit to one, while all other Operation Control Register bits are set to 0, puts the AS3910 into Initial NFC Target mode. In this low power mode, only the Target Activation Detector, which will detect a presence of external RF field, is active. Once the presence of external RF field is detected, an interrupt is sent to microcontroller which will in turn switch on oscillator and receiver. 8.2 Transmitter The Transmitter contains two identical driver blocks which are driving external antenna connected to pins RFO1 and RFO2. The driver is composed of 8 segments having binary weighted output resistance. The MSB segment typical ON resistance is 3; when all segments are turned on, the output resistance is typically 1.5. Usually certain segments are switched off to define AM modulated level, while they are all turned on to define the non-modulated level. It is also possible to switch off certain segments when driving the non modulated level to reduce the amplitude of signal on the antenna and/or to reduce the antenna Q factor. The driver impedance in increased in case of AM modulation (ISO-14443B), in case of OOK modulation (ISO-14443A) both drivers are blocked to low state. In the single driver mode (bit sing of configuration register 2 set to 1) only RFO1 output is driven, RFO2 output is disabled. AM modulation and operation of the driver segments is controlled by writing AM modulation depth and antenna driver registers (see AM Modulation Depth and Antenna Driver Registers on page 32). Register #13 defines which segments will be used to define normal, nonmodulated level. The default setting is that all segments are used. Registers #10 to #12 are used to define how the AM modulated level is set-up. It can be set-up automatically by definition of modulation depth and the direct command Calibrate Modulation Depth or by a direct definition of segments which are turned off during AM modulation. 8.3 Receiver The receiver performs demodulation of the transponder subcarrier modulation which is superimposed on the 13.56 MHz carrier frequency. It performs AM or PM demodulation, band-pass filtering and digitalization of subcarrier signals, 848, 424 and 212 kHz subcarrier frequencies are supported. Additionally, it performs RSSI measurement, automatic gain control (AGC) and Squelch function. The receiver is switched on when Operation Control Register bit rx_en is set. The operation of the receiver is additionally controlled by the signal rx_on which is set high when modulated signal is expected on the receiver input. This is automatically done after every Transmit command. Signal rx_on can be also forced high by sending direct command Unmask Receive Data. Signal rx_on is used to control features like RSSI and AGC. AM demodulation is performed using a peak follower. Both the positive and negative peaks are tracked to suppress common mode signal. In case external demodulation is carried out the peak follower stage can be bypassed by setting bit envi in Configuration Register 2. In case of PM demodulation signal coming from the phase detector is replacing the output of peak follower. Next stage in signal processing is the buffer amplifier followed by second order low pass filter with adjustable corner frequency. Final stage is a first order high pass filter with adjustable corner frequency. The digital signal representing transponder subcarrier modulation is produced by a window comparator. Filter setting is done automatically when ISO mode and data rate are chosen by writing ISO Mode Definition Register. Setting is displayed in the Receiver Configuration Register (#06) and can be changed by rewriting this register. In transparent mode ISO mode register is not used and Filter selection has to be done by writing Receiver Configuration register (#06). By setting the Operation Control Register bit rx_lp receiver operates in low power mode. In this mode, power consumption is lower but as consequence also receiver sensitivity is reduced (see Electrical Characteristics on page 8). www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 13 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.3.1 Gain Reduction, AGC and Squelch The total gain of receiver chain is 160. In certain conditions it is desirable to reduce this gain. There are several features implemented in the Receiver to reduce this gain. Automatic Gain Reduction (AGC). AGC (automatic gain control) feature is useful in case the transponder is close to the reader. In such conditions receiver chain is in saturation and demodulation can be influenced by system noise and saturation of last gain stage. When AGC is switched on receiver gain is reduced so that the input to digitizer stage is not saturated. The AGC system comprises a window comparator which has its window three times larger then window of digitalization window comparator. When the AGC function is enabled gain is reduced until there are no transitions on its output. Such procedure assures that the input to digitalization window comparator is less then three times larger than its window. AGC operation is controlled by the Receiver Configuration Register (#06) bits agc_en and agc_m. Agc_en bit enables AGC operation, agc_m defines AGC operating mode. The AGC action is started 20s after rising edge of signal rx_on. In case agc_m bit is 0 it will operate during a complete receive period, in case it is 1 it will operate on first 8 subcarrier pulses. The AGC is reducing gain to -21dB in 7 steps of 3dB. When signal rx_on is low AGC is in reset. Squelch. This feature is designed to avoid demodulation problems of transponders which produce a lot of noise during data processing which takes place when the data sent by the reader is being processed and an answer prepared. It can also be used in noisy environment. Transponder processing noise (or environment noise) may be misinterpreted as start of transponder response which results in reader decoding error. These problems are avoided by reducing receiver gain so that there are no transitions of output when noise is present. This is done by sending direct command Squelch. During execution of the direct command Squelch the digital output of receiver (output of window comparator mentioned above) is observed. In case there are more then two transitions on this output in 50s time period, gain is reduced for 3dB and output is observed during next 50s. This procedure is repeated until number of transitions in 50s is lower or equal to 2 or until maximum gain reduction (21dB) is reached. This setting is cleared with direct command Clear Squelch. Setting Gain Reduction in Receiver Configuration Register (#06). By setting bits rg2 to rg0 in Receiver Configuration Register (#06) receiver gain can also be reduced in 7 steps of 3dB. Actual gain reduction is combination of all three gain reduction features mentioned above (AGC, Squelch and setting gain reduction in Receiver Configuration Register). Actual gain reduction state can also be observed by reading the Receiver State Display Register (#17) bits gr_2 to gr_0. 8.3.2 RSSI The receiver also comprises of an RSSI block (Received Signal Strength Indicator) which measures the strength of the modulated signal that is superimposed on the 13.56MHz carrier. RSSI is a peak hold system which is started 20s and 16 transitions of demodulated signal after rising edge of rx_on. It stays active while signal rx_on is high; while rx_on is low it is frozen. Result of RSSI measurements is 4 bit value which can be observed by reading Receiver State Display Register (#17) bits rssi_3 to rssi_0. The RSSI range calculated back on RFI1 input is 280Vrms to 8.8mVrms, one LSB represents step of 2.15dB. Since the RSSI measurement is a peak hold then the RSSI result will not follow any variations in the signal strength (the highest value will be kept). In such a case it is possible to reset RSSI bits of Receiver State Display Register and restart the measurement by sending direct command Clear RSSI. 8.3.3 AM and PM Demodulation In addition to usual AM demodulation, the AS3910 also includes the possibility of PM demodulation. Readers which have only AM demodulation may have so called communication holes in operating volume. Communication holes are areas where transponder is not seen, they depend on transponder characteristics such as Q factor and resonant frequency variation. Usually both AM and PM modulation are present, in so called communication holes receiver input signal is only PM modulated. Choice between AM and PM demodulation is done by setting the bit pmd in the Configuration Register 5 (#05); default setting is AM. As mentioned above an RSSI measurement is continually done while transponder message is being processed. By comparing RSSI value in AM and PM mode the external controller can opt for the demodulation mode in which there is more signal. PM demodulation is done by processing phase signal coming from the Phase Detector. 8.4 A/D Converter The AS3910 contains an 8 bit successive approximation A/D converter. Input to A/D converter can be multiplexed from different sources to be used in several direct commands and adjustment procedures. The result of last A/D conversion is stored in a register which can be read through the SPI interface (address #0D). Typical conversion time is 12s. The A/D converter has two operating modes, absolute and relative. In absolute mode the low reference is 0V and the high reference is 2V. This means that A/D converter input range is from 0 to 2V, 00 code means input is 0V or lower, FF means that input is 2V or higher, LSB is 7.8125mV. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 14 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n In relative mode low reference is 1/6 of VSP and high reference is 5/6 of VSP, so the input range is from 1/6VSP to 5/6VSP. Relative mode is only used in phase measurement in which phase detector output is proportional to power supply. In all other cases absolute mode is used. The A/D converter input can also be accessed externally. When the direct command AD Convert is sent, an A/D conversion of voltage present on pin AD_IN is performed in absolute mode, result is stored in A/D Converter Output Register. AD_IN pin should be left non-connected in case A/ D conversion is not needed in application. 8.5 Phase and Amplitude Detector 8.5.1 Phase Detector The phase detector is observing phase difference between the transmitter output signals (RFO1 and RFO2) and the pad signals RFI1 and RFI2, which are proportional to the signal on the antenna LC tank. These signals are first passed by digitizing comparators. Digitized signals are processed by a phase detector. Filter characteristics of the phase antenna are adapted to one of the two possible operation modes. For antenna tuning check, a strong low power filter is used to get average phase difference, for PM demodulation a low pass filter having 1MHz corner frequency is used to pass the subcarrier frequency. Antenna Tuning Check. The Phase Detector output reflects phase relationship between the two inputs. The 90 phase shift (ideal antenna LC tank tuning) results in VSP/2 output voltage. In case the antenna LC tank is detuned, phase shift changes which results in different phase detector output voltage. In case of command Check Antenna Resonance phase detector output is applied to A/ D converter in relative mode. Output of phase detector is also observed by comparator with reference signal VSP/2. Output of this comparator is used in execution of direct command Calibrate Antenna. PM Demodulation. The phase detector has low pass characteristics in case of PM demodulation. This is to allow phase demodulation of the 848 kHz subcarrier signal. The output is then fed to Receiver. 8.5.2 Amplitude Detector Signals from pads RFI1 and RFI2 are used as inputs to the self mixing stage. Output of this stage is DC voltage proportional to amplitude of signal on RFI1 and RFI2 pads. This signal is fed to A/D converter when amplitude of signal on RFI inputs has to be measured (direct commands Measure RF and Calibrate Modulation Depth). 8.6 External Field Detector The External Field Detector is used in NFC mode to detect the presence of an external RF field. It is composed of two sub-blocks, Target Activation Detector and a RF Collision Avoidance Detector. Input to both blocks is the signal from the RFI1 pad. The thresholds of the two blocks can be independently set by writing the NFCIP Field Detection Threshold Register (#14). The outputs of both detectors are fed to a logic or gate, output of which goes to the Control logic. A low to high transition of this logic or gate output triggers an interrupt (Interrupt due to nfc event) 8.6.1 Target Activation Detector This block is turned on in NFC target mode to detect the presence of an interrogator field. It is enabled by setting the Operation Control Register bit nfc_t. It is a low power block with an adjustable threshold in the range from 145mVpp and 590mVpp. This block generates an interrupt when an external field is detected and also when it disappears. With such implementation it can also be used to detect the moment when the external field disappears. This is useful to detect the moment when external NFC device (it can either an interrogator or a target) has stopped emitting an RF field since a response can only be sent afterwards. Actual state of the Target Activation Detector can be checked by reading the bit rfp in the Receiver State Display Register (#17). When this bit is set to logic one there is a signal higher then the threshold present on the input of Target Activation Detector. 8.6.2 RF Collision Avoidance Detector This block is activated during the RF Collision Avoidance sequence which is executed before every request or response in NFC active communication (Initial or Response RF Collision Avoidance). In case during the RF Collision Avoidance sequence the presence of an external field is detected, request/response is not sent, an interrupt is generated to inform the external controller about collision. During RF Collision Avoidance, the Target Activation Detector is disabled in order to have the correct threshold when detection is made. The threshold of the RF Collision Avoidance Detector can be adjusted in the range from 50 to 1080mVpp. 8.7 Quartz Crystal Oscillator The quartz crystal oscillator can operate with 13.56MHz and 27.12MHz crystals. The oscillator is based on an inverter stage supplied by controlled current source. A feedback loop is controlling the bias current in order to regulate amplitude on XTI pin to 1Vpp. This feedback assures reliable operation even in case of low quality crystals with Rs up to 50. In order to enable a fast reader start-up an interrupt is sent when oscillator amplitude exceeds 750mVpp. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 15 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n The oscillator block always provides 13.56MHz clock signal to the rest of the IC. In case of 27.12MHz crystal clock signal is internally divided by two. Divider is controlled by Configuration Register 2 (#02) bit osc. Division by two assures that 13.56 MHz signal has a duty cycle of 50% which is better for the Transmitter performance (no PW distortion). Use of 27.12MHz crystal is therefore recommended for better performance. In case of 13.56MHz crystal, the bias current of stage which is digitizing oscillator signal is increased to assure as low PW distortion as possible. The oscillator output is also used to drive a clock signal output pin which can be used by the external microcontroller (MCU_CLK). By setting bits in Configuration Register 2 MCU_CLK a frequency can chosen between 13.56MHz, 6.78MHz and 3.39MHz. Any microcontroller processing generates noise which may be captured by the AS3910 receiver. Using MCU_CLK as the microcontroller clock source generates noise which is synchronous to the reader carrier frequency and is therefore filtered out by the receiver while using some other incoherent clock source produces noise which may generate some sideband signals captured by Receiver. Due to this fact it is recommended to use MCU_CLK as microcontroller clock source. 8.8 Power Supply, Regulators The AS3910 includes two regulators which can be adjusted automatically to improve the reader PSRR. VDD is an external power supply pin. It is used to supply the logic and digital pins. One regulator is used to supply analog blocks (VSP_A), another is there just for transmitter (VSP_RF) in order to decouple transmitter current spikes from the rest of the IC. All negative power supply pins are externally connected to the same negative supply, the reason for separation is in decoupling of noise induced by voltage drops on the internal power supply lines. These pins are VSS (die substrate potential), VSN_D (negative supply of logic and digital pads), VSN_A (negative supply of analog blocks) and VSN_RF (negative supply of transmitter). An additional regulator block provides AGD voltage (1.5V) which is used as reference potential for analog processing (analog ground). Blocking capacitors have to be connected externally to regulator outputs and AGD pins. For pins VSP_A and VSP_RF recommended blocking capacitors are 2.2F in parallel with 10nF, for pin AGD 1F in parallel with 10nF is suggested. The regulated voltage range is from 2.4V to 3.4V with step of 100mV. Both regulators are set to the same voltage. VSP_A regulator maximum capability is 20mA while maximum capability of VSP_RF regulator is 300mA. VSP_RF regulator also has a built in protection which limits current to max 300mA in normal operation and to max 500 mA in case of a short. The regulators are operating when either the Operating Control Register bit en is set or pin EN is high. In Power-down mode the regulators are not operating, VSP_A and VSP_RF are connected to VDD through 1k resistors. Connection through resistors assures smooth power up of the system and a smooth transitions from Stand-by mode to other operating modes. In case regulators were regulating or were transparent at power up a huge current would be pulled from VDD supply to charge blocking capacitors of regulated outputs which is especially problematic for battery powered systems. At power up the regulated voltage is set to maximum voltage (3.4V). The regulator voltage can then be set automatically or "manually". Automatic procedure is started by sending the direct command Adjust Regulators. In this procedure regulated voltage is set 250mV below VDD. This procedure assures that reader operates with maximum possible power while still assuring good PSRR. Regulator operation can be controlled and observed by writing and reading two Regulator registers. Regulator Display Register (#15) is a read only register which displays actual regulated voltage when regulator is operating. In Power-down mode its content is forced to 00. By writing Regulated Voltage Definition Register (#16) user chooses between automatic and "manual" adjustment of regulated voltage. Automatic mode is chosen when bit reg_s is 0 (default and also recommended state). When bit reg_s is asserted to 1 regulated voltage is defined by bits rege_3 to rege_1 of the same register. 8.9 Communication to External Microcontroller The AS3910 is a slave device and the external microcontroller initiates all communication. Communication is done by a 4-wire Serial Peripheral Interface (SPI). The AS3910 asks microcontroller for its attention by sending an interrupt (pin INTR). In addition the microcontroller can use clock signal available on pin MCU_CLK when the oscillator is running. The microcontroller can also drive pin EN. Putting this pin high has the same function as setting the Operation Control Register bit en (entry in Ready mode). www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 16 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.9.1 Serial Peripheral Interface (SPI) Maximum Operation Frequency of the Serial Peripheral Interface is 20 MHz. Table 6. Serial Peripheral Interface (4-wire Interface) Signal Lines Name SEN SDATAI SDATAO SCLK Signal Digital Input with pull down Digital Input Digital Output with tristate Digital Input Signal Level CMOS CMOS CMOS CMOS SPI Enable Serial Data input Serial Data output Clock for serial communication Description 8.9.2 SPI Operation MODE Bits When signal SEN is low, the SPI interface is in reset and SDATAO is in tristate; when it is high, SPI interface is enabled. It is recommended to keep signal SEN low whenever the SPI interface is not in use. SDATAI is sampled at the falling edge of SCLK. All communication is done in blocks of 8 bits (bytes). First two bits of first byte transmitted after low to high transition of SEN define SPI operation mode. Table 7 defines possible modes: Table 7. SPI Operation Patterns 8.9.3 Writing of Data to Addressable Registers (WRITE Mode) SDATAI is sampled at the falling edge of SCLK (see Figure 5, Figure 6). A SEN LOW pulse indicates the end of the WRITE command after register has been written. Auto incrementing address is supported, which means that if after the address and first data byte some additional data bytes are sent, they are then written to addresses incremented by 1. In case the command is terminated by putting SEN low before a packet of 8 bits composing one byte is sent, writing of this register is not performed. In case the register on the defined address does not exist or it is a read only register, no write is performed. Following examples show cases of writing a single byte and writing multiple bytes with auto-incrementing address. Figure 5. Writing of a Single Byte (falling edge sampling) SEN SCLK SDATAI X 0 0 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 X SEN falling edge signals end of WRITE Mode Two leading Zeros indicate WRITE Mode SCLK raising edge data is transferred from C SCLK falling edge Data is sampled Data is moved to Address A5-A0 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 17 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Figure 6. Writing of Register Data with Auto-Incrementing Address SEN SCLK SDATAI X 00 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 X SEN falling edge signals end of WRITE Mode Two leading Zeros indicate WRITE Mode Data is moved to Address Data is moved to Address Data is moved to Address Data is moved to Address 8.9.4 Reading of Data from Addressable Registers (READ Mode) The command control Byte for a read command consists of a command code and an address. After the command code, the address of register to be read has to be provided from the MSB to the LSB. Then one or more data bytes can be transferred from the SPI slave to the master, always from the MSB to the LSB. As in case of the write command also the read command supports auto-incrementing address. To transfer bytes from consecutive addresses, SPI master has to keep the SEN signal high and the SCLK has to be active as long as data need to be read from the slave. SDATAI is sampled at the falling edge of SCLK (like shown in the following diagrams), data to be read from the AS3910 internal register is driven to SDATAO pin on rising edge of SCLK and is sampled by the master (C) at the falling edge of SCLK. A SEN LOW pulse has to be performed after register data has been transferred in order to indicate the end of the READ command and prepare the Interface to the next command control Byte. In case the register on defined address does not exist all 0 data is sent to SDATAO. Figure 7 illustrates an example for reading of a single byte. Figure 7. Reading of a Single Register Byte SEN SCLK SDATAI 0 1 A5 A4 A3 A2 A1 A0 X SDATAO X SCLK raising edge data is transferred from C SCLK falling edge Data is sampled D7 D6 D5 D4 D3 D2 D1 D0 X SEN falling edge signals end of READ Mode 01 pattern indicates READ Mode SCLK raising edge Data is moved from Address SCLK falling edge Data is transferred to C www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 18 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.9.5 Sending Direct Commands Direct commands have no arguments, so a single byte is sent. Command mode is entered if the SPI is started with two leading ONE. After the COMMAND mode code 11 (see Table 9), the six bit command code is sent MSB to the LSB. The command is executed on falling edge of SEN. During the direct command execution, starting another activity over the SPI interface is not allowed. Figure 8. Sending Direct Commands SEN SCLK SDATAI X 1 1 C5 C4 C3 C2 C1 C0 X SEN falling edge signals start of command execution Two leading ONE indicate COMMAND Mode SCLK raising edge data is transferred from C SCLK falling edge Data is sampled 8.9.6 Loading Transmitting Data into FIFO Loading the transmitting data into the FIFO is similar to writing data into an addressable registers. Difference is that in case of loading more bytes all bytes go to the FIFO. The command mode code 10 indicates FIFO operations. In case of loading transmitting data into FIFO all bits SEN SCLK SDATAI X 1 0 0 0 0 0 0 0 Start of payload Data 1 to 32 bytes X SEN falling edge signals end of COMMAND Mode 10 pattern indicates FIFO mode SCLK raising edge data is transferred from C SCLK falling edge Data is sampled 8.9.7 Reading Received Data from FIFO Reading received data from the FIFO is similar to reading data from an addressable registers. Difference is that in case of reading more bytes they all come from the FIFO. The command mode code 10 indicates FIFO operations. In case of reading the received data from the FIFO all bits 8.9.8 Interrupt Interface When an interrupt condition is met the source of interrupt bit is set in the Interrupt Register and the INTR pin transitions to high. The microcontroller then reads the Interrupt Register to distinguish between different interrupt sources. After the Interrupt Register is read its content is reset to 0 and INTR pin signal transitions to low. Note: There may be more then one Interrupt Register bit set in case the microcontroller did not immediately read the Interrupt Register after the INTR signal was set and another event causing interrupt occurred. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 19 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n In case an interrupt from a certain source is not required it can be disabled by setting corresponding bit in the Mask Interrupt Register. In case of masking a certain interrupt source the interrupt is not produced, but the source of interrupt bit is still set in Interrupt Register. After reading the Interrupt Register the 13.56MHz clock coming from the oscillator is used to produce a reset signal which clears it and resets INTR signal. Practically in all interrupt cases the oscillator is running when an interrupt is produced. The only exception is the interrupt in the Initial NFC Target mode where only the Target Activation Detector is operating. In this case the interrupt is cleared with first SCLK rising edge following reading of the Interrupt Register (an extra dummy CLK pulse during reading of the Interrupt Register or first SCLK pulse of the next SPI command will do the job). Table 8. Serial Peripheral Interface (4-wire Interface) Signal Lines Name INTR Signal Digital Output Signal Level CMOS Description Interrupt Output pin 8.9.9 FIFO Water Level and FIFO Status Register The AS3910 contains a 32 byte FIFO. In case of transmitting the Control logic shifts data which was previously loaded by the external microcontroller to the Framing Block and further to the Transmitter. During reception, the demodulated data is stored in the FIFO and the external microcontroller can download received data once reception was terminated. Transmit and receive capability the AS3910 is not limited by of the FIFO size due to a FIFO water level interrupt system. During transmission an interrupt is sent (interrupt due to FIFO water level) when the content of data in the FIFO which still need to be sent is lower then the FIFO water level for receive. The external microcontroller can now add more data in the FIFO. The same stands for receive mode. In case the number of received bytes gets over the FIFO water level for receive an interrupt is sent to inform the external controller that data has to be downloaded from FIFO. The external controller has to serve the FIFO faster then data is transmitted or received. A general rule is that the SCLK frequency has to be at least double then the actual data rate in receive or transmit. There are two settings of the FIFO water level available for receive and transmit in Configuration Register 5 (#05). After data is received the external microcontroller needs to know how long the receive data string was before downloading data from the FIFO: This information is available in the FIFO Status Register (#09) which displays number of bytes in the FIFO which were not read out. The FIFO Status Register also contains a FIFO overflow bit. This bit is set when during reception the external processor did not react on time and more then 32 bytes were written in FIFO. The received data is of course lost in such a case. 8.10 Direct Commands Table 9. Direct Commands Code 000001 000010 000100 000101 000110 000111 001000 001001 001010 010000 010001 010010 010011 Command Set default Clear Transmit with CRC Transmit without CRC Transmit REQA Transmit WUPA NFC transmit with Initial RF Collision Avoidance Stops all activities and clears FIFO Starts a transmit sequence using automatic CRC generation Starts a transmit sequence without automatic CRC generation Transmits REQA command (ISO-14443A mode only) Transmits WUPA command (ISO-14443A mode only) Equivalent to Transmit with CRC with additional RF Collision Avoidance Comments Puts the AS3910 in default state (same as after power-up) NFC transmit with Response RF Collision Equivalent to Transmit with CRC with additional RF Collision Avoidance Avoidance NFC transmit with Response RF Collision Equivalent to Transmit with CRC with additional RF Collision Avoidance Avoidance with n=0 Mask receive data Unmask receive data AD convert Measure RF Receive after this command is ignored Receive data following this command is normally processed (this command has priority over internal mask receive timer) A/D conversion of signal on AD_IN pin is performed, result is stored in A/D Converter Output Register RF amplitude is measured, result is stored in A/D Converter Output Register www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 20 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 9. Direct Commands Code 010100 010101 010110 010111 011000 011001 011010 011100 Command Squelch Clear Squelch Adjust regulators Calibrate modulation depth Calibrate antenna Check antenna resonance Clear RSSI Transparent mode Comments Performs gain reduction based on the current noise level. Resumes gain settings which were in place before sending Squelch command Adjusts supply regulators according to the current supply voltage level Starts sequence which activates the TX, measures the modulation depth and adapts it to comply with the specified modulation depth Starts the sequence to adjust parallel capacitances connected to TRIMx pins so that the antenna LC is in resonance. Measurement of antenna LC tank resonance to determine whether calibration is needed. Clears RSSI bits and restarts the measurement Enter in Transparent mode 8.10.1 Set Default This direct command puts the AS3910 in the same state as power-up initialization. All registers are initialized to the default state. Please note that results of different calibration and adjust commands are also lost. This direct command is accepted in all operating modes. 8.10.2 Clear This direct command stops all current activities (transmission or reception) and clears FIFO. It also clears Collision and Interrupt Registers. This command has to be sent first in a sequence preparing a transmission (except in case of direct commands Transmit REQA and Transmit WUPA). 8.10.3 Transmit Commands All Transmit commands (Transmit with CRC, Transmit without CRC, Transmit REQA and Transmit WUPA) are only accepted in case the Transmitter is enabled (bit tx_en is set). 8.10.4 NFC Transmit Commands The NFC transmit commands (NFC transmit with Initial RF Collision Avoidance, NFC transmit with Response RF Collision Avoidance, NFC transmit with Response RF Collision Avoidance with n=0) are used to transmit requests and responses in the NFC mode. Before actual transmission the RF Collision avoidance with Collision avoidance threshold defined in the NFCIP Field Detection Threshold Register is performed. In the command NFC transmit with Response RF Collision Avoidance n is randomly set in a range from 0 to 3, while in the command NFC transmit with Response RF Collision Avoidance with n=0 it is set to 0. In case collision is detected during the RF Collision Avoidance the transmission is not done and an interrupt is sent with flag INTR due to NFC event. The NFC transmit commands switch on and off the transmission block, setting the Operation control bit tx_en in the NFC mode is not allowed. Timing of the NFC transmit commands is according to the ISO/IEC 18092 standard. For some timings the ISO/IEC 18092 specifies a range. Actual implementation in the AS3910 is the following: Parameter Initial delay time RF waiting time Initial guard time Active delay time Active guard time Guard time after sending response or request Symbol TIDT TRWF TIRFG TADT TARFG TGAS Value 302 37.76 5.11 151 84 65 Unit s s ms s s s Initial RF Collision Avoidance Response RF Collision Avoidance Response RF Collision Avoidance TGAS is the time during which RF field stays switched on after sending a response or request. This time is not specified in the ISO/IEC 18092. Note Initial RF Collision Avoidance An interrupt due to end of transmission is sent when RF field is switched off. All NFC Transmit commands are only authorized in case the ISO mode configuration bit nfc is set and the oscillator and regulators are running. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 21 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.10.5 Mask Receive Data and Unmask Receive Data After the direct command Mask Receive Data the signal rx_on which enables the RSSI and AGC operation of the Receiver (see Receiver on page 13) is forced to low, processing of the receiver output by the framing block is disabled, all received modulation is rejected. This command is useful to block receiver and receive framing from processing the data when there is actually no input and only a noise would be processed (for example in case where a transponder processing time after receiving a command from the reader is long). The direct command Unmask Receive Data is enabling normal processing of the received data (signal rx_on is set high to enable the RSSI and AGC operation, the framing block is enabled. A common use of this command is to enable again the receiver operation after it was disabled by the command Mask Receive Data. Another possible use is in case one wants that the receive processing starts immediately after the transmit command (usually the receiver operation is enabled 40 s after the transmission is terminated). This is accomplished by sending the Unmask Receive Data immediately after the end of transmission interrupt is received. The command Unmask Receive Data has to be used in the NFC target mode. The sequence implemented in the AS3910 supposes that every action is started with a transmit command, after sending the transmit data, the receive mode is automatically entered to process the response. Such a sequence is always in place in case of the ISO-14443 reader mode and also in case of the NFCIP mode where the AS3910 is the initiator. In case of the NFC target mode this sequence is started by receiving the interrogator request. After the interrupt caused by the first initiator request command Unmask Receive Data is sent to force the AS3910 in receive mode. The commands Mask Receive Data and Unmask Receive Data are only accepted when the Receiver is operating. 8.10.6 AD Convert A/D conversion of signal on AD_IN pin is performed; result is stored in A/D Converter Output Register (see A/D Converter on page 14). Duration time: 42s max. This command is accepted in any mode where the oscillator and regulators are running. 8.10.7 Measure RF This command measures the amplitude on the RFI inputs and stores result in the A/D Converter Output Register (see also A/D Converter and Amplitude Detector on page 15). When this command is executed the output of the Amplitude detector is multiplexed to the A/D converter input (the A/D converter is in absolute mode). The Amplitude Detector conversion gain is 0.6 Vinpp/Vout. One LSB of the A/D converter output represents 13.02mVpp on the RFI inputs, a 3Vpp signal which is maximum allowed level on each of the two RFI inputs results in 1.8V output DC voltage and would produce the value of 1110 0110 on the A/D converter output. Duration time: 42s max. This command is accepted in any mode where the oscillator and regulators are running. 8.10.8 Squelch This direct command is intended to avoid demodulation problems of transponders which produce a lot of noise during data processing (while data sent by reader is processed and answer prepared). It can also be used in a noisy environment. The operation of this command is explained in Squelch - refer to page 14. Duration time: 500s max This command is only accepted when the Transmitter and Receiver are operating. 8.10.9 Clear Squelch Clears the gain reduction which was established by sending Squelch command. This command is accepted in any mode. 8.10.10 Adjust Regulators When this command is sent the power supply level of VDD is measured in maximum load conditions and the regulated voltage reference is set 250 mV below this measured level to assure maximum possible stable regulated supply (see Power Supply, Regulators on page 16). Using this command increases the system PSSR. At the beginning of execution of this command, both the receiver and transmitter are switched on to have the maximum current consumption, the regulators are set to the maximum 3.4V regulated voltage. After 300s VSP_RF is compared to VDD, in case VSP_RF is not at least 250mV lower the regulator setting is reduced for one step (100mV) and measurement is done after 300s. Procedure is repeated as long as VSP_RF drops 250mV below VDD of until minimum regulated voltage (2.4V) is reached. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 22 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Duration time: 5ms max This command is accepted in any mode where the oscillator and regulators are running. This command is not accepted in case the external definition of the regulated voltage is selected in the Regulated Voltage Definition Register (#16, bit reg_s is set to H) 8.10.11 Calibrate Modulation Depth Starts a patent pending sequence, which activates the transmission, measures the modulation depth and adapts it to comply with the modulation depth specified in the Modulation Depth Definition Register (#10). When calibration procedure is finished result is displayed in Modulation Depth Display Register. Please see AM Modulation Depth Definition Using Direct Command Calibrate Modulation Depth (page 40) for details about setting the AM modulation depth and running this command. Duration time: 10ms max This command is accepted in any mode where the oscillator and regulators are running. 8.10.12 Calibrate Antenna Sending this command starts a patent pending sequence which adjusts the parallel capacitances connected to TRIMx pins so that the antenna LC is in resonance. See Calibrate Antenna Resonance on page 42 for details. Duration time: 400s max This command is accepted in any mode where the oscillator and regulators are running. 8.10.13 Check Antenna Resonance This command measures the antenna LC tank resonance to determine whether a calibration is needed. See Check Antenna Resonance on page 42 for details. Duration time: 42s max. This command is accepted in any mode where the oscillator and regulators are running. 8.10.14 Clear RSSI The Receiver automatically clears the RSSI bits in the Receiver State Display Register and starts to measure the RSSI when the signal rx_on is asserted. Since the RSSI bits store peak value (peak-hold type) eventual variation of the receiver input signal will not be followed (this may happen in case of long message or test procedure). The direct command Clear RSSI clears the RSSI bits in the Receiver State Display Register, the RSSI measurement is restarted (in case of course rx_on is still high). 8.10.15 Transparent Mode Enter in the Transparent mode. The Transparent mode is entered on the falling edge of signal SEN and is maintained as long as signal SEN is kept low. See Transparent Mode on page 43 for details about the Transparent Mode. This command is only accepted when the Transmitter and Receiver are operating. 8.11 Registers The 6 bit register addresses below are defined in the hexadecimal notation. The possible address range is from 00(hex) to 3F(hex). A sign # before a number is used in this document to reference a hexadecimal number. There are two types of registers implemented in the AS3910: configuration registers and display registers. The configuration registers are used to configure the AS3910. They can be written and read through the SPI (RW). The display registers are read only (RO); they contain information about the AS3910 internal state which can be accessed through the SPI. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 23 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.11.1 Main Registers Table 10. ISO Mode Definition Register Address # 00: ISO Mode Definition Register Bit 7 6 5 4 Name nfc b_a tx_rate2 tx_rate1 Def. 0 0 0 0 Function 1=NFC, 0=ISO-14443 1=ISO-14443B, 0=ISO-14443A tx_rate2 0 0 0 3 tx_rate0 0 0 1 2 1 rx_rate2 rx_rate1 0 0 rx_rate2 0 0 0 rx_rate0 0 0 0 1 tx_rate1 0 0 1 1 x rx_rate1 0 0 1 1 x tx_rate0 0 1 0 1 x rx_rate0 0 1 0 1 x bit rate 106kb/s 212kb/s 424kb/s 848kb/s RFU bit rate 106kb/s 212kb/s 424kb/s 848kb/s RFU Selects ISO-14443 data rate for receive, Applicable in case nfc=0 Selects ISO-14443 data rate for transmit, Applicable in case nfc=0 type: RW Comments NFC means NFCIP-1, 106 kbps active communication mode Applicable in case nfc=0 Note: In case nfc=1, then both transmit and receive data rates are set to 106kbps independent of TX and RX setting. Default setting is set at power up and after Set Default command. Table 11. Operation Control Register Address # 01: Operation Control Register Bit 7 6 5 4 3 2 1 0 Note: Receive low power operation sacrifices the input sensitivity for low consumption. If Rx consumption is reduced from 10mA to 5mA, then a 10mA reader operation is possible. Default setting is set at power up and after Set Default command. Not used Name en rx_en rx_lp tx_en nfc_t Def. 0 0 0 0 0 Function en=1 enables oscillator and regulator (Ready mode) rx_en=1 enables receiver operation rx_lp=1 low power receiver operation tx_en=1 enables RF output nfc_t =1 enables Initial NFC Target mode At the moment RF field is detected, interrupt is sent. Receive consumption is reduced type: RW Comments Is internally ORed with the EN pin www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 24 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.11.2 Configuration Registers Table 12. Configuration Register 2 Address # 02: Configuration Register 2 Bit 7 6 5 4 3 2 Name sing envi tf2 tf1 osc out_cl1 Def. 0 0 0 0 0 0 Function 1 only RFO1 driver will be used 1 input applied to RFI1 is envelope 1 reduces the gain for 11 dB in first stage after peak detector type: RW Comments Choose between single and differential driving of antenna. RF envelope input When both bits are set there is 17 dB gain 1 reduces the gain for 6 dB in first stage after reduction in first stage peak detector 0 13.56MHz Xtal, 1 27.12MHz Xtal out_cl1 0 0 1 1 Not used out_cl0 0 1 0 1 out_cl 3.39MHz 6.78 MHZ 13.56 MHZ no output Selection of clock frequency on MCU_CLK output. In case of "11", MCU_CLK output is permanently low. Selector for crystal oscillator 1 out_cl0 0 0 Note: Default setting is set at power up and after Set Default command. Table 13. Configuration Register 3 Address # 03: Configuration Register 3 (ISO-14443A and NFC) Bit 7 Name crc_rx Def. 0 1 receive without CRC Function type: RW Comments For ISO-14443A anticollision. When set to 1 parity bits are still detected and removed before received data is put in FIFO, but there is no check for their correctness p_len0 0 1 1 reduction 0 74ns 1106ns Modulation pulse reduction, Defined in number of 13.56 MHz clock periods 0 0 1 Not used 6 5 4 3 2 1 0 no_par p_len3 p_len2 p_len1 p_len0 0 0 0 0 0 1 no byte parity checking p_len3 0 0 1 p_len2 0 0 1 p_len1 Note: Default setting is set at power up and after Set Default command. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 25 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 14. Configuration Register 4 Address # 04: Configuration Register 4 (ISO-14443B) Bit 7 6 Name egt2 egt1 Def. 0 0 egt2 0 0 5 egt0 0 1 1 4 3 2 1 0 sof_0 sof_1 eof egt 0 0 0 0 egt1 0 0 1 1 Function egt0 0 1 0 1 number of EGT 0 1 6 6 SOF, number of etu with logic 0 (10 or 11) SOF, number of etu with logic 1 (2 or 3) EOF, number of etu with logic 0 (10 or 11) EGT time defined in number of etu type: RW Comments 0 10 etu, 1 11 etu 0 2 etu, 1 3 etu 0 10 etu, 1 11 etu 0 no EGT after last character, 1 EGT after each character Not used Note: Default setting is set at power up and after Set Default command. Table 15. Configuration Register 5 Address # 05: Configuration Register 5 Bit 7 Name pmd Def. 0 Function 1 PM demodulation 0 AM demodulation 0 OOK, 1 AM type: RW Comments AM/PM demodulation selection Valid for Transparent mode. For ISO-14443 and NFC modes, modulation type is set automatically (ISO-14443A and NFC is OOK, ISO-14443B is AM) (see Table 26) 6 5 4 3 2 1 0 am 0 Not used fifo_lr fifo_lt 0 0 0 28, 1 24 0 4, 1 8 Not used FIFO water level for receive FIFO water level for transmit Note: Default setting is set at power up and after Set Default command. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 26 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 16. Receiver Configuration Register Address # 06: Receiver Configuration Register Bit 7 6 5 4 Name agc_en agc_m rg2 rg1 Def. 0 0 0 0 1 AGC is enabled 1 AGC operate on first eight subcarrier pulses 0 AGC operate during complete receive period rg2 0 0 3 rg0 0 1 rg1 0 0 1 rg0 0 1 1 Gain reduction 0 3 dB 21 dB Filter selection is automatically set when ISO mode or receive data rate change (Change of ISO mode definition register). After automatic preset filter, selection can be changed by writing these bits. Gain reduction in 3dB steps. From 0 to 21dB. AGC operation mode Function type: RW Comments 2 fs2 0 fs2 fs1 fs0 Filter Selection Comment 1 fs1 0 0 0 0 0 1 1 1 0 0 1 1 0 1 1 0 1 0 1 0 0 1 ISO-14443A 106 kb/s ISO-14443B 106 kb/s ISO-14443A/B 212 kb/s ISO-14443A/B 424 kb/s ISO-14443A/B 848 kb/s 424/484 kHz subcarriers 212 kHz Automatic preset Automatic preset Automatic preset Automatic preset Automatic preset No automatic preset No automatic preset 0 fs0 0 Other combinations not supported or used for block testing purposes Note: Default setting is set at power up and after Set Default command, filter selection bits are preset also when ISO mode or receive data rate change. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 27 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.11.3 Interrupt Register and Associated Registers Table 17. Mask Interrupt Register Address # 07: Mask Interrupt Register Bit 7 6 5 4 3 2 1 0 Name M_osc M_nfc M_wl M_rxs M_txe M_err M_crc M_col Def. 0 0 0 0 0 0 0 0 Function mask INTR when oscillator frequency is stable mask INTR due to nfc event mask INTR due to FIFO water level mask INTR due to end of receive mask INTR due to end of transmission mask INTR due to error in receive data coding mask INTR due to CRC error mask INTR due to bit collision type: RW Comments Note: Default setting is set at power up and after Set Default command. Table 18. Interrupt Register Address # 08: Interrupt Register Bit 7 6 Name I_osc I_nfc Function INTR when oscillator frequency is stable INTR due to nfc event Set after enable Set when nfc_t is 1 and en=0 informing that an RF field has been detected, Set when transmission could not be done due to detection of RF field during RF Collision Avoidance Set during receive, informing that FIFO is almost full and has to be read out. Set during transmit, informing that FIFO is almost empty and that additional data has to be sent. type: R Comments 5 4 3 2 1 0 I_wl I_rxs I_txe I_err I_crc I_col INTR due to FIFO water level INTR due to end of receive INTR due to end of transmission INTR due to error in receive data coding INTR due to CRC error INTR due to bit collision This includes parity error and framing error Valid only for ISO-14443A Note: At power up and after Set Default command, content of this register is set to 0. After Interrupt register read, its content is set to 0 Table 19. FIFO Status Register Address # 09: FIFO Status Register Bit 7 6 5 4 3 2 Name fifo_b5 fifo_b4 fifo_b3 fifo_b2 fifo_b1 fifo_b0 Number of bytes (binary coded) in the FIFO which were not read out Valid range is from 000000 to 100000 Function type: R Comments www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 28 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 19. FIFO Status Register Address # 09: FIFO Status Register Bit 1 0 Name fifo_ovr rx_act FIFO overflow Active receive. This bit is set to 1 when start of By reading this bit it can be checked whether transponder is transponder message is detected and stays high until answering. See also Application Notes (Active receive). end of receive. Function type: R Comments Note: At power up and after direct commands, Set Default and Clear content of this register is set to 0. Table 20. Collision Register Address # 0A: Collision Register (for ISO-14443A only) Bit 7 6 5 4 3 2 1 0 Name c_byte3 c_byte2 c_byte1 c_byte0 c_bit2 c_bit1 c_bit0 rfu Not used, always 0 Number of bits before the collision in the byte where the collision happened Number of full bytes before the bit collision happened Function type: R Comments Note: At power up and after direct commands Set Default and Clear content of this register is set to 0. Table 21. Number of Transmitted Bytes Register 0 Address # 0B: Number of Transmitted Bytes Register 0 Bit 7 6 5 4 3 2 1 0 frm4 antcl 0 0 Name ntx1 ntx0 nbtx2 nbtx1 nbtx0 Def. 0 0 0 0 0 Not used 4bit response frame ISO-14443 anticollision frame Has to be set to 1 when 4bit response frame is expected (Mifare Ultralight) Has to be set to 1 when ISO-14443A bit oriented anticollision frame is sent Function type: RW Comments Number of bytes to be transmitted in one command, Maximum supported number of bytes is 1023 LSB bits Number of bits in the split byte 000 means that all bytes all full Applicable only to ISO-14443A bit oriented anticollision frame in case last byte is split byte Note: Bits frm4 and antcl are cleared after transmission is performed. Default setting is set at power up and after Set Default command. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 29 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 22. Number of Transmitted Bytes Register 1 Address # 0C: Number of Transmitted Bytes Register 1 Bit 7 6 5 4 3 2 1 0 Name ntx9 ntx8 ntx7 ntx6 ntx5 ntx4 ntx3 ntx2 Def. 0 0 0 0 0 0 0 0 Number of bytes to be transmitted in one command, Maximum supported number of bytes is 1023 MSB bits Function type: RW Comments Note: Default setting is set at power up and after Set Default command 8.11.4 A/D Converter Output Register Table 23. A/D Output Register Address # 0D: A/D Output Register Bit 7 6 5 4 3 2 1 0 Name ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 Displays results of A/D conversion. Function type: R Comments Note: At power up and after Set Default command, content of this register is set to 0. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 30 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.11.5 Antenna Calibration Registers Table 24. Antenna Calibration Register Address # 0E: Antenna Calibration Register Bit 7 6 5 4 3 2 1 0 Note: At power up and after Set Default command content of this register is set to 0. Table 25. External Trim Register Address # 0F: External Trim Register Bit 7 6 5 4 3 2 1 0 Note: Default setting is set at power up and after Set Default command. Not used Name trim_s tre_3 tre_2 tre_1 tre_0 Def. 0 0 0 0 0 LSB Function 0 LC trim switches are defined by result of Calibrate antenna command 1 LC trim switches are defined by bits tre_x written in this register MSB LC trim switches are defined by data written in this register in case trim_s=1. A bit set to 1 switch on transistor on TRIM1_x and TRIM2_x pin. type: RW Comments Defines source of driving switches on TRIMx pins Not used Name tri_3 tri_2 tri_1 tri_0 tri_err LSB 1 antenna calibration error Function MSB type: R Comments This register stores result of Calibrate antenna command. LC trim switches are defined by data written in this register in case trim_s=0. A bit set to 1 indicates that corresponding transistor on TRIM1_x and TRIM2_x pin is switched on. Set when Calibrate antenna sequence was not able to adjust resonance www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 31 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.11.6 AM Modulation Depth and Antenna Driver Registers Table 26. Modulation Depth Definition Register Address # 10: Modulation Depth Definition Register Bit 7 6 5 4 3 2 1 0 Note: Default setting is set at power up and after Set Default command. Table 27. Modulation Depth Display Register Address # 11: Modulation Depth Display Register Bit 7 6 5 4 3 2 1 0 Name md_7 md_6 md_5 md_4 md_3 md_2 md_1 md_0 LSB Displays result of Calibrate Modulation Depth command. Antenna drivers are composed of 8 binary weighted segments. Bit md_x set to one indicates that this particular segment will be disabled during AM modulated state. Function MSB type: R Comments Name am_s mod5 mod4 mod3 mod2 mod1 mod0 Def. 0 0 0 0 0 0 LSB See Application Notes for details about AM modulation level definition. Function 0 AM modulated level is defined by bits mod5 to mod0. Level is adjusted automatically by Calibrate Modulation Depth command 1 AM modulated level is defined by bits dram7 to dram0. MSB type: RW Comments Note: At power up and after Set Default command content of this register is set to 0. Table 28. Antenna Driver AM Modulated Level Definition Address # 12: Antenna Driver AM Modulated Level Definition Bit 7 6 5 4 3 2 1 0 Name dram7 dram6 dram5 dram4 dram3 dram2 dram1 dram0 Def. 0 0 0 0 0 0 0 0 LSB Antenna drivers are composed of 8 binary weighted segments. Setting a bit dram to 1 will disable corresponding segment during AM modulated state in case am_s bit is set to 1. Function MSB type: RW Comments Note: Default setting is set at power up and after Set Default command. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 32 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 29. Antenna Driver Non-Modulated Level Definition Address # 13: Antenna Driver Non-Modulated Level Definition Bit 7 6 5 4 3 2 1 0 Name droff7 droff6 droff5 droff4 droff3 droff2 droff1 droff0 Def. 0 0 0 0 0 0 0 0 LSB Antenna drivers are composed of 8 binary weighted segments. Setting a bit droff to 1 will disable corresponding segment during normal non-modulated operation. Function MSB type: RW Comments Note: Default setting is set at power up and after Set Default command. 8.11.7 NFCIP Field Detection Threshold Register Table 30. NFCIP Field Detection Threshold Address # 14: NFCIP Field Detection Threshold Bit 7 6 5 4 3 2 1 0 Name trg_l3 trg_l2 trg_l1 trg_l0 rfe_t3 rfe_t2 rfe_t1 rfe_t0 Collision avoidance threshold LSB Target activation level LSB Collision avoidance threshold MSB Threshold used to detect presence of external field during collision avoidance. See Table 32 for threshold definition. Def. Function Target activation level MSB Threshold used to detect presence of interrogator magnetic field. See Table 31 for threshold definition. type: RW Comments Note: Default setting is set at power up and after Set Default command. Table 31. Target Activation Threshold as seen on RFI1 Input trg_l3 x 0 0 0 1 0 0 1 0 trg_l2 0 0 0 0 0 1 1 0 1 trg_l1 0 0 1 1 0 0 0 1 1 trg_l0 0 1 0 1 1 0 1 0 0 Target activation threshold voltage [mVpp on RFI1] forbidden (measurement is deactivated) 590 420 350 350 300 265 265 235 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 33 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 31. Target Activation Threshold as seen on RFI1 Input trg_l3 0 1 1 1 1 1 trg_l2 1 0 1 1 1 1 trg_l1 1 1 0 0 1 1 trg_l0 1 1 0 1 0 1 Target activation threshold voltage [mVpp on RFI1] 220 220 190 175 155 145 Table 32. Collision Avoidance Threshold as seen on RFI1 Input rfe_3 x 0 0 0 0 1 0 1 0 1 1 0 1 1 1 rfe_2 0 0 0 0 1 0 1 0 1 0 1 1 1 1 1 rfe_1 0 0 1 1 0 0 0 1 1 1 0 1 0 1 1 rfe_0 0 1 0 1 0 1 1 0 0 1 0 1 1 0 1 Collision avoidance threshold voltage [mVpp on RFI1] forbidden (measurement is deactivated) 50 67 88 120 145 172 185 240 255 340 350 480 700 1080 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 34 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.11.8 Regulator Registers Table 33. Regulators Display Register Address # 15: Regulators Display Register Bit 7 6 5 4 3 2 1 0 Note: At power up and after Set Default command, regulated voltage is set to maximum 3.4V. Table 34. Regulated Voltage Definition Register Address # 16: Regulated Voltage Definition Register Bit 7 6 5 4 3 2 1 0 Note: Default setting is set at power up and after Set Default command. Table 35. Definition reg_3 rege_3 1 1 1 1 1 1 1 1 0 0 reg_2 rege_2 1 1 1 1 0 0 0 0 1 1 reg_1 rege_1 1 1 0 0 1 1 0 0 1 1 reg_0 rege_0 1 0 1 0 1 0 1 0 1 0 Regulated voltage [V] 3.4 3.3 3.2 3.1 3.0 2.9 2.8 2.7 2.6 2.5 Not used Name reg_s rege_3 rege _2 rege _1 rege _0 Def. 0 0 0 0 0 LSB Function 0 regulated voltages are defined by result of Adjust regulators command 1 regulated voltages are defined by rege_x bits written in this register MSB External definition of regulated voltage. See Table 35 for definition. type: RW Comments Defines mode of regulator voltage setting Not used Name reg_3 reg_2 reg_1 reg_0 LSB MSB This register displays actual regulated voltage when regulator is operating. In Power-down mode, its content is forced to 00. See Table 35 for definition. Function type: R Comments www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 35 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Table 35. Definition reg_3 rege_3 0 reg_2 rege_2 1 other combinations reg_1 rege_1 0 reg_0 rege_0 1 Regulated voltage [V] 2.4 2.4 Receiver State Display Register Table 36. Receiver State Display Register Address # 17: Receiver State Display Register Bit 7 6 5 4 3 2 1 Name rssi_3 rssi_2 rssi_1 rssi_0 oscok/rfp gr_2 gr_1 LSB Unlatched osc_ok flag in case nfc=0 Target activation detector output in case nfc=1 gr_2 0 0 0 gr_0 1 gr_1 0 0 1 gr_0 0 1 1 Gain reduction 0 3 dB 21 dB Displays status of receiver gain reduction (result of AGC, gain reduction setting and Squelch command) MSB Function type: R Comments Stores peak value of RSSI measurement. Automatically cleared at beginning of transponder message and with Clear RSSI command. Note: At power up and after Set Default command, content of this register is set to 0. rssi_3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 rssi_2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 rssi_1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 rssi_0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Signal on RFI1 [mVrms] 0 ~ 0.28 0.28 ~ 0.35 0.35 ~ 0.45 0.45 ~ 0.57 0.57 ~ 0.74 0.74 ~ 0.95 0.95 ~ 1.21 1.21 ~ 1.56 1.56 ~ 2.00 2.00 ~ 2.55 2.55 ~ 3.27 3.27 ~ 4.20 4.20 ~ 5.37 5.37 ~ 6.88 6.88 ~ 8.80 >8.80 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 36 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.12 Typical Operating Sequence At power up the AS3910 enters in the Stand-by mode. Content of all registers is set to the default state which is in most cases 0. First action of the microcontroller after a power-up should be to load the ISO Mode Definition Register and the configuration registers to configure reader operation. Since the regulators are by default set to the maximum 3.4V, which means that they are at supply voltages lower then 3.4V transparent, it is advised to send the direct command Adjust Regulators to improve the system PSRR. In case the LC tank trimming is implemented the direct command Calibrate Antenna has to be sent. In case the AM modulation will be used (ISO-14443B for example) setting the modulation depth in the Modulation Depth Definition Register and sending the command Calibrate Modulation Depth is suggested next. After the sequence of events mentioned above the AS3910 is ready to operate. 8.12.1 ISO-14443 Reader Operation First the Ready mode has to be entered by setting the en bit of the Operation Control Register (address #01 or asserting pin EN). In this mode the oscillator is started and the regulators are enabled. When the oscillator operation is stable an interrupt is sent. Before sending any command to a transponder the transmitter and receiver have to be enabled by setting the bits rx_en and tx_en. In case REQA or WUPA has to be sent, then it is simply done by sending the appropriate direct command. Or else, the following sequence has to be followed: Send the direct command Clear Define the number of transmitted bytes in the registers 0B and 0C Write the bytes to be transmitted in the FIFO Send the direct command Transmit with CRC or Transmit without CRC (whichever is appropriate) When all the data is transmitted, an interrupt is sent to inform the microcontroller that the transmission is finished (INTR due to end of transmission). After the transmission is executed, the AS3910 receiver automatically starts to observe the RFI inputs to detect a transponder response. The RSSI and AGC (in case it is enabled) are started. The framing block processes the subcarrier signal from receiver and fills the FIFO with data. When the reception is finished and all the data is in the FIFO an interrupt is sent to the microcontroller (INTR due to end of receive), additionally the FIFO Status Register displays the number of bytes in the FIFO so the microcontroller can proceeded with downloading the data. In case there was an error or bit collision detected during reception, an interrupt with appropriate flag is sent. Microcontroller has to take appropriate action. In case of an error it usually repeats the command; it can also check the RSSI level in the Receiver State Display Register and change the AM/ PM mode in case the RSSI is low. In case of a bit collision it will consult the Collision Register to determine in which bit there was collision. 1. 2. 3. 4. 5. Transmit and Receive In Case Data Packet is Longer Than FIFO. In case a data packet is longer then FIFO the sequence explained above is modified. Before transmit the FIFO is filled. During transmit an interrupt is sent when remaining number of bytes is lower then the water level (INTR due to FIFO water level). The microcontroller in turn adds more data in the FIFO. When all the data is transmitted an interrupt is sent to inform the microcontroller that transmission is finished. During reception situation is similar. In case the FIFO is loaded with more data than the receive water level, an interrupt is sent and the microcontroller in turn reads the data from the FIFO (additionally to the interrupt the FIFO Status Register displays the number of bytes which were not read out). When reception is finished an interrupt is sent to the microcontroller (INTR due to end of receive), additionally the FIFO Status Register displays the number of bytes in the FIFO which are still to be read out. 8.12.2 NFCIP-1 Operation Only the NFCIP-1 106 kbps active mode is supported. For operation in this mode, the bit nfc has to be set in the ISO Mode Definition Register. Next the NFCIP Field Detection Threshold Register (address #14) has to be written to define the thresholds for Target activation and RF Collision avoidance (see External Field Detector on page 15). Please note that in the NFC mode the transmitter enable bit (tx_en) is never set in the Operation Control Register. The transmitter is activated automatically by the NFC transmit commands). www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 37 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n NFCIP Target. The AS3910 enters in the Initial NFC Target mode by setting the nfc_t bit in the Operation Control Register. In this low power mode only the Target Activation Detector is running. At the moment presence of external the RF field is detected an interrupt is sent (INTR due to nfc event). The microcontroller can now activate the oscillator, regulators and receiver. As explained in Target Activation Detector - refer to page 15, the Target Activation Detector may also be used to detect the moment when initiator turns off its RF field. In case the delay time, after which the initiator turns off its field after sending its request, is known, this feature is not needed and the Target Activation Detector can be turned off by setting bit nfc_t low after presence of the initiator field is detected. Next the direct command Unmask Receive Data has to be send to put the Receiver and control logic in the receive mode. The AS3910 is now ready to receive request from the initiator. Procedure during the reception is the same as in case of the ISO-14443 mode. The target response is done in the same way as in case of the ISO-14443 transmission, only that the command which actually starts the transmission is either NFC transmit with Response RF Collision Avoidance or NFC transmit with Response RF Collision Avoidance with n=0. These two commands perform the RF Collision avoidance procedure before actually starting the transmission. In case an external RF field is detected during the RF Collision avoidance procedure an interrupt is sent (INTR due to nfc event) and the transmission is not performed. Next the AS3910 expects a new request from the initiator. In case the Target Activation Detector is still enabled an interrupt will be generated when the initiator switch on its field. This is additional information for the external controller, but it is not required by the receiver. The receiver is already running, reception will be done automatically and an interrupt will be sent when reception will be completed (or when the FIFO water level will be reached in case of a long request). NFCIP Initiator. In case the AS3910 is an NFCIP initiator, the microcontroller activates the oscillator and receiver and prepares everything for transmitting as in case of the ISO-14443 transmission. The transmission is actually executed by direct command NFC Transmit with Initial RF Collision Avoidance. Following events are the same as described in previous chapter only that roles of the initiator and target are interchanged. The Target Activation Detector may also be used in case of the NFCIP initiator operation to detect the moment when the target RF field turns on and off. 8.13 ISO-14443A SELECT SEQUENCE In the 14443A select sequence the commands REQA (also WUPA), ANTICOLLISION and SELECT are used. For the commands REQA and WUPA the short frame is used, for ANTICOLLISION the bit oriented anticollision frame is used, for SELECT the standard frame is used. Transponder replies to commands REQA, WUPA and ANTICOLLISION do not contain the CRC so the configuration bit crc_rx of the Configuration Register 3 (address 03) has to be set to 1 (receive without CRC) before these commands are sent. 8.13.1 REQA and WUPA Sending of these two commands is simple since they are implemented as the AS3910 direct commands (Transmit REQA and Transmit WUPA). Procedure is the following (note that since the ATQA response does not contain a CRC the configuration bit crc_rx of the Configuration Register 3 (address #03) has to be set to 1 before this procedure is started): 1. Send the direct command Transmit REQA (or Transmit WUPA) 2. When all the data is transmitted an interrupt is sent to inform the microcontroller that transmission is finished (INTR due to end of transmission) 3. When reception of the ATQA is finished and all data is in the FIFO an interrupt is sent to the microcontroller (INTR due to end of receive), additionally the FIFO Status Register displays number of bytes (2 bytes in case of ATQA) in the FIFO so the microcontroller can proceeded with downloading data from the FIFO. Sending the direct command Clear before sending Transmit REQA and Transmit WUPA is not necessary. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 38 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.13.2 ANTICOLLISION In this command, the bit oriented anticollision frame is used. There is no CRC, neither in the command send from PCD to PICC (part 1 of the bit oriented anticollision frame), nor in the reply sent from PICC to PCD (part 2 of the bit oriented anticollision frame). Due to this configuration the bit crc_rx of the Configuration Register 3 (address #03) has to be set to 1 before. Sequence in case full bytes are transmitted (no collision during the transponder response): 1. Send the direct command Clear 2. Define the number of transmitted bytes for part1 of the bit oriented anticollision frame in the registers #0B and #0C. Bit 0 (antcl) of register #0B has to be additionally set to 1 to indicate that anticollision frame is sent. 3. Write the bytes to be transmitted in the FIFO 4. Send the direct command Transmit without CRC 5. When all the data is transmitted an interrupt is sent to inform the microcontroller that transmission is finished (INTR due to end of transmission) 6. When the reception of part2 of the bit oriented anticollision frame is finished and there was no collision detected, data is put in the FIFO and an interrupt is sent to microcontroller (INTR due to end of receive), additionally the FIFO Status Register displays the number of bytes in the FIFO, so the microcontroller can proceeded with downloading data from the FIFO. Sequence in case of a split byte (no collision during transponder response): 1. Send the direct command Clear 2. Define the number of full bytes and the number of bits in the split byte to be transmitted in the registers #0B and #0C (bits ntx define the number of full bytes, bits nbtx in register #0B define the number of bits in the split byte). Bit 0 (antcl) of register #0B has to be additionally set to 1 to indicate that anticollision frame is sent. 3. Write the bytes to be transmitted in FIFO. Since the SPI communication is byte oriented 8 bits have to transferred also for split byte (sent last), the MSB bits of split byte which are not transmitted are don't care. 4. Send the direct command Transmit Without CRC 5. When all the data is transmitted an interrupt is sent to inform the microcontroller that the transmission is finished (INTR due to end of transmission) 6. When the reception of part2 of the bit oriented anticollision frame is finished and there was no collision detected, data is put in the FIFO and an interrupt is sent to the microcontroller (INTR due to end of receive), additionally the FIFO Status Register displays the number of bytes in the FIFO so the microcontroller can proceeded with downloading data from the FIFO. First downloaded byte contains second part of the split byte, so only the MSB part of byte which was not sent during transmit is valid. 8.13.3 Collision Detection The AS3910 Framing block is able to detect the bit collision in case of presence of more ISO-14443A transponders. This feature is very useful during the select sequence. The collision is detected during the ANTICOLLISION command (different transponders have different UIDs); it may already be detected in the ATQA (answer to REQA or WUPA). When the bit collision is detected an interrupt is sent (INTR due to collision) and the bit at which collision occurred is indicated in the Collision Register (#0A). In case of anticollision frame (indicated to the AS3910 by bit 0 of register #0B) the bit collision position displayed in Collision Register is counted from beginning of anticollision frame (including the part which is transmitted). Please note that after getting the interrupt due to collision, the reader has to wait that the transponders finish sending their messages before sending a new command. The end of transponder message is indicated by the End of Receive interrupt. It may also happen that the interrupt due to collision and due to end of receive are read at the same time (in case reaction to the first interrupt is slow and collision happens at the end of transponder message). There is also a slight possibility that the end of message flag is just written to the Interrupt Register while it is being erased at the end of the Interrupt Register read due to the collision interrupt. In such a case there is no end of receive interrupt. In case it is not clear whether the receive logic is still processing response the Active Receive bit (rx_act) in FIFO Status Register can be consulted (See ISO-14443B, Reduction of TR0 and TR1 and Suppression of EOF/SOF in PICC Response on page 44 for details about Active Receive bit). 8.13.4 SELECT The SELECT command uses standard frame, response to the SELECT command (SAK) contains also a CRC, so before sending this command the configuration bit crc_rx of Configuration Register 3 has to be reset back to 0. Since the SELECT command contains CRC the direct command Transmit with CRC can be used. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 39 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.14 Receiving 4Bit Tag Response Frame Mifare Ultralight tag uses 4 bit response frame to indicate ACK and NACK. The AS3910 framing expects that response frame is composed of bytes (except in case of anticollision frame) and it rejects a 4 bit response frame as an error (error due to receive data coding). By setting the bit 1 (frm4l) of register #0B, a 4 bit response frame is correctly processed and put in FIFO (MSB bits of first byte). In case of setting this bit a standard frame response is not processed correctly. Response to Mifare Ultralight WRITE command is either ACK or NACK. So in case of this command bit frm4 has to be set to distinguish between the two possible 4 bit responses. Response to READ command is either a standard frame, in case command is correctly processed, or a NACK, in case of an error. In this case the bit frm4 can not be used, interrupt due to receive data coding should be interpreted as a NACK. 8.15 AM Modulation Depth: Definition and Calibration The AM modulation of the transmitted carrier is used for communication reader to transponder in two configuration cases: The ISO-14443B mode is configured in the ISO Mode Definition Register (#01) The Transparent mode with AM modulation [direct command Transparent Mode, the bit 6(am) of the Configuration Register 5 (#05) is set to 1] In other cases the OOK modulation is used. The AM modulation depth can be automatically adjusted by setting the Modulation Depth Definition Register (#10) and sending the direct command Calibrate Modulation Depth. This procedure is patent pending. There is also an alternative possibility where the command Calibrate Modulation Depth is not used and the modulated level is defined by writing the Antenna driver AM Modulated Level Definition Register (#12). 8.15.1 AM Modulation Depth Definition Using Direct Command Calibrate Modulation Depth Before sending the direct command Calibrate Modulation Depth the Modulation Depth Definition Register (#10) has to be configured in the following way: The bit 7 (am_s) has to be set to 0 to chose definition by the command Calibrate Modulation Depth The bits 6 to 1 (mod5 to mod0) define target AM modulation depth. Definition of Modulation Depth Using Bits mod5 to mod0. The RFID standard documents usually define the AM modulation level in form of the modulation index. The modulation index is defined by formula (a-b)/(a+b) where `a' is amplitude of the non-modulated carrier and `b' is the amplitude of the modulated carrier. The modulation index specification is different for different standards. The ISO-14443B modulation index is typically 10% with allowed range from 8% to 14%, range from 10 to 30% is defined in the ISO-15693 and 8% to 30% in the FelicaTM. The bits mod5 to mod0 are used to calculate the amplitude of the modulated level. The non-modulated level which was before measured by the A/D converter and stored in an 8 bit register is divided by a binary number in range from 1 to 1.98. The bits mod5 to mod0 define binary decimals of this number. Example: In case of the modulation index 10% the modulated level amplitude is 1.2222 times lower then the non-modulated level. 1.2222 converted to binary and truncated to 6 decimals is 1.001110. So in order to define the modulation index 10% the bits mod5 to mod0 have to be set to 001110. The table below depicts setting of the mod bits for some often used modulation indexes. Table 37. Setting mod bits for Modulation Indexes modulation index [%] 8 10 14 20 30 33 a/b [dec] 1,1739 1,2222 1,3256 1,5000 1,8571 1,9843 a/b [bin] 1,001011 1,001110 1,010100 1,100000 1,110111 1,111111 mod5.........mod0 001011 001110 010100 100000 110111 111111 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 40 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Execution of Direct Command Calibrate Modulation Depth. The modulation level is adjusted by increasing the RFO1 and RFO2 driver output resistance. The RFO drivers are composed of 8 binary weighted segments. Usually all these segments are turned on to define the normal, non-modulated level, there is also a possibility to increase the output resistance of the non-modulated state by writing the Antenna driver non-modulated level definition register (#13). Before sending the direct command Calibrate Modulation Depth the oscillator and regulators have to be turned on. When the direct command Calibrate Modulation Depth is sent the following procedure is executed: 1. The Transmitter is turned on, non-modulated level is established 2. The amplitude of the non-modulated carrier level established on the inputs RFI1 and RFI2 is measured by the A/D converter and stored in the A/D Converter Output Register 3. Based on the measurement of the non-modulated level and the target modulated level defined by the bits mod5 to mod0 the target modulated level is calculated 4. The output driver control is taken over by the eight bit Calibrate Register with initial level defined in the Antenna Driver Non-Modulated Level Definition Register (#13). Content of the Calibrate Register is incremented by 1 to increase the driver resistance, the reduced amplitude is measured by the A/D converter and the result is compared to the target modulation level. 5. The procedure from previous point is repeated as long as the measured level is greater then target level. 6. When the measured level is equal or lower than the target level, actual state of the Calibrate Register is copied in the Modulation Depth Display Register (#11). Content of this register is used to define the AM modulated level. Note: After this calibration procedure is finished, the content of Antenna driver non-modulated level definition register (#13) should not be changed. Modification of this register content will change the non-modulated amplitude and therefore the ration between the modulated and non-modulated level will be changed. Please also note that in case the Calibration of antenna resonant frequency in implemented command Calibrate Antenna has to be run before AM modulation depth adjustment. 8.15.2 AM Modulation Depth Definition Using Antenna Driver AM Modulated Level Definition Register (#12) When the bit 7 (am_s) of the Modulation Depth Definition Register (#10) is set to 1 the AM modulated level is controlled by writing the Antenna Driver AM Modulated Level Definition Register (#12). In case setting of the modulated level is already known it is not necessary to run the calibration procedure, the modulated level can simply be defined by writing this register. There is also a possibility to run a calibration procedure from externally using the Antenna driver non-modulated level definition register (#13) and the direct command Measure RF. The procedure is the following: 1. Write the non-modulated level in register #13 (usually it is all 0 to have the lower possible output resistance) 2. Switch on the transmitter 3. After the settling time (10s should be enough), send the direct command Measure RF. Read result from the A/D Converter Output Register (#0E) 4. Calculate the target modulated level from the target modulation index and result from the previous point 5. In the following iterations content of the register #13 is modified, the command Measure RF performed and result compared to the target modulated level as long as the result is not equal or close enough to the target modulated level. 6. At the end the content of the register #13 which results in the target modulated level is written in the Antenna Driver AM Modulated Level Definition Register (#12) while the register #13 is restored with the non-modulated level definition value. 8.16 Antenna LC Tank Resonance: Checking and Calibration The AS3910 comprises the building blocks which make possible checking and adjustment of the antenna LC tank resonance frequency. The arrangement of these building blocks and associated adjustment procedure are patent pending. The key block in the resonance frequency checking and adjustment is the Phase Detector (see Phase Detector on page 15). The Phase Detector is measuring the phase shift between the Transmitter output signals (RFO1 and RFO2) and the inputs RFI1 and RFI2, which are proportional to voltage on the antenna LC tank. In case of perfect tuning there is a 90 phase shift between them. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 41 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.16.1 Check Antenna Resonance In case of the perfect 90 phase shift mentioned above, the Phase Detector output results in VSP/2 output voltage. A phase shift of 1% of the carrier frequency period (3.6) results in the output voltage change of 2% of VSP (1% phase shift results in 60mV change at VSP=3V). During execution of the direct command Check Antenna Resonance the Phase Detector output is multiplexed on the input of A/ D converter which is set in relative mode. 1 LSB of the A/D conversion output represents 0.13% of carrier frequency period (0.468). The result of A/D conversion is in case of the perfect tuning exactly in the middle of range (1000 0000 or 0111 1111). Value higher then 1000 0000 means that phase detector output voltage is higher then VSP/2, which corresponds to case with resonance frequency higher then target 13.56 MHz. In the opposite case, when the resonance frequency is lower then target, the result of A/D conversion is lower then 0111 1111. Execution of the command Check Antenna Resonance is fast and it can be used frequently to check whether system settings are correct. 8.16.2 Calibrate Antenna Resonance In order to implement the antenna LC tank calibration binary weighted trimming capacitors have to be connected between the two coil terminals to the pads TRIM1_3 to TRIM1_0 and TRIM2_3 to TRIM2_0. In case single driver is used only the pads TRIM1_3 to TRIM1_0 are used, pads TRIM2_3 to TRIM2_0 are left open. Figure 10 depicts connection of the trim capacitors for both, single and differential driving. The TRIM pads contain the HVNMOS switch transistors to VSS. During trimming procedure the resonance frequency is adjusted by connecting some of the trimming capacitors to VSS and leaving others floating. The switches of the same binary weight are driven from the same source and are both on or off (the switches TRIM1_2 and TRIM2_2 are for example both either on of off). The breakdown voltage of the HVNMNOS switch transistors is 30V, which limits the maximum peak to peak voltage on LC tank in case trimming is used. The on resistance of TRIM1_0 and TRIM2_0 switch transistors which are meant to be connected to LSB trimming capacitor is typ 50 at 3V VSP, the on resistance of other pads is binary weighted (the on resistance of TRIM1_3 and TRIM2_3 is 6.25). Figure 10. Connection of Trimming Capacitors to the Antenna LC Tank in case of Single (left) and Differential Driving (right) TRIM 1_0 TRIM 1_1 TRIM 1_2 TRIM 1_3 RF01 RF02 RFI 1 RFI 2 Antenna TRIM 1_0 TRIM 1_1 TRIM 1_2 TRIM 1_3 RF01 RF02 RFI 1 RFI 2 1/2 Antenna 1/2 Antenna TRIM 2_3 TRIM 2_2 TRIM 2_1 TRIM 2_0 TRIM 2_3 TRIM 2_2 TRIM 2_1 TRIM 2_0 www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 42 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n Antenna Calibration Using Command Calibrate Antenna. The calibration of LC tank resonance frequency is automatically done by running the direct command Calibrate Antenna. During execution of this command the comparator at the output of Phase Detector is used. In case the LC tank resonance frequency is higher then the target 13.56MHz, the Phase Detector output gets higher then VSP/2 and the comparator output is high. In the opposite case, when the resonance frequency is lower, the Phase Detector output gets lower then VSP/2 and the comparator output is low. At the beginning of the command Calibrate Antenna execution the switches in all TRIM pads are turned off. As consequence all the trimming capacitors are disconnected so in case the LC tank dimensioning is correct the resonance frequency has to be higher then the target and the comparator output has to be high. In case the comparator output is low at this initial state the resonance frequency is too low even when all the trimming capacitor are disconnected and adjusting of the resonance frequency is not possible. An error flag is set and execution of the command is terminated. In case the comparator output was high at the initial state, the LSB switches (TRIM1_0 and TRIM2_0) are switched on and after 10s state of the comparator output is checked again. This procedure is repeated until the comparator output transitions to low or until the final state with all switches turned on is reached. The switch state at which the comparator output transitioned is the one at which the LC tank is in resonance. In case the state with all switched turned on was reached and the comparator output is still high, the resonance frequency is too high even when all the capacitors are connected and the adjusting is not possible. The error flag is set. The result of the direct command Calibrate Antenna can be observed by reading the Antenna Calibration Register (#0E). This register displays the state of four bits representing state of the switches when resonance was reached and the error flag. After the execution of direct command Calibrate Antenna the resonance can be checked by running the direct command Check Antenna Resonance. Antenna Calibration Using External Trim Register. There is also a possibility to control the position of the TRIM switches by writing the External Trim Register (#0F). When the bit trim_s of this register is set to 1 position of the trim switches is controlled by bits tre_3 to tre_0. Using this register and the direct command Check Antenna Resonance a trimming procedure may be implemented from externally. Another possibility of external trimming procedure is using this register and the direct command Measure RF. In this case the resonance is adjusted by looking for operating point with the maximum amplitude. 8.17 Transparent Mode The AS3910 framing supports the ISO-14443 standard. Other standard and custom 13.56MHz RFID reader protocols can be realized using the AS3910 AFE and framing implemented in the external microcontroller. After sending the direct command Transparent Mode the external microcontroller directly controls the transmission modulator and gets the Receiver output (control logic becomes "transparent"). The Transparent Mode is entered on falling edge of signal SEN after sending the command Transparent Mode and is maintained as long as the signal SEN is kept low. Before sending the direct command Transparent Mode the Transmitter and Receiver have to be turned on, the AFE have to be configured properly. While the AS3910 is in the Transparent Mode the AFE is controlled directly through SPI interface: The Transmitter modulation is controlled by pin SDATAI (high is modulator on) Signal rx_on is controlled by pin SCLK (high enables RSSI and AGC) The Receiver output is sent to pin SDATAO By controlling the rx_on advanced Receiver features like the RSSI and AGC can be used. Configuration bits related to the ISO mode, framing and FIFO are of course meaningless in Transparent Mode, all other configuration bits are respected. For communication reader to transponder the OOK and AM modulation are supported. Type of the modulation is defined by writing the bit 6 (am) of the Configuration Register 5 (#05). The direct command Calibrate Modulation Depth supports modulation depths up to 30%, by writing the AM Modulated Level Definition Register (#12) also definition of deeper am modulation is possible. The Receiver filters support the subcarrier frequencies from 212 kHz to 848 kHz. The filter characteristics are defined by writing the bits fs2 to fs0 in the Receiver Configuration Register (#6). www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 43 - 47 AS3910 Data Sheet - A p p l i c a t i o n I n f o r m a t i o n 8.18 Active Receive - Use in ISO-14443B Anticollision Usually the microcontroller does not need information about beginning of the transponder message, it gets an interrupt once reception is finished or earlier in case the transponder message is longer then the FIFO. In some cases the information about the fact that the receiver is already processing a message from the transponder is useful. The bit rx_act in the FIFO Status Register (address 09) provides this information. This bit is set to 1 when start of the transponder message is detected and stays high until the end of reception. This information can be used to speed up the ISO-14443B anticollision procedure when more slots are used. In case there is no message in a certain slot the reader does not have to wait the time message ATQB takes before sending the next Slot-MARKER command, it can send it as soon as it is clear that there is no answer in that particular slot. The microcontroller can obtain this info by reading the rx_act flag at the time the receiver should already be processing the ATQB message. In case rx_act flag is set to one the receiver is processing a message and the microcontroller has to wait for the end of receive interrupt, in opposite case when the rx_act flag is set to zero there is no ATQB message in that particular slot and the next Slot-MARKER command can be sent immediately. 8.19 ISO-14443B, Reduction of TR0 and TR1 and Suppression of EOF/SOF in PICC Response The ISO-14443-3 standard, chapter 7.10.3 Coding of Param 1 defines possibility to reduce the TR0 and TR1 and suppress the EOF/SOF in PICC response. Note: The AS3910 Receiver and Framing blocks do not support the reduction of TR0 and TR1 and suppression of EOF/SOF. In case default settings of these parameters are changed, the framing block will not be able to decode the PICC response. 8.20 Test Pins Pins TEST and TIO are used to test the AS3910. Pin TEST is a digital pin with pull down, it is used to enter the test mode, pin TIO is used in test mode as a digital IO, in normal mode it is in tristate. It is recommended to connect pin TEST to VSS and to leave pin TIO open. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 44 - 47 AS3910 Data Sheet - P a c k a g e D r a w i n g s a n d M a r k i n g s 9 Package Drawings and Markings The devices are available in a 32-pin QFN (5x5mm) package. Figure 11. 32-pin QFN (5x5mm) Package Symbol A A1 A3 b D E D2 Notes: Min 0.80 0.00 0.18 Typ 0.85 0.203 REF 0.23 5.00 BSC 5.00 BSC 3.30 Max 0.90 0.05 0.30 3.20 3.40 Symbol E2 e L L1 P aaa ccc Min 3.20 0.35 Typ 3.30 0.50 BSC 0.40 45 BSC 0.15 0.10 Max 3.40 0.45 0.10 1. Dimensioning and tolerancing conform to ASME Y14.5M-1994. 2. All dimensions are in millimeters, angle are in degrees. 3. Dimension b applies to metallized terminal and is measured between 0.25 and 0.30mm from terminal tip. Dimension L1 represents terminal full back from package edge up to 0.1mm is acceptable. 4. Coplanarity applies to the exposed heat slug as well as the terminal. 5. Radius on terminal is optional. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 45 - 47 AS3910 Data Sheet - R e v i s i o n H i s t o r y Revision History Revision 1.0 2.1 Date Dec 01, 2008 April 08, 2009 July 01, 2009 Owner Mark Maks Mauro Description Initial version Complete datasheet updated Updated ordering information (see Table 38) 1) Parameter values updated in Table 5 - Electrical Characteristics 2) Updated bits 5,4 in Table 12 and bits 1,0 in Table 21 3) Updated "ANTICOLLISION - refer to page 39" and "Collision Detection - refer to page 39" 4) Inserted information in "Receiving 4Bit Tag Response Frame - refer to page 40" Updated General Description (page 1), Ordering Information (page 47) 1) Pin type for pins 7, 9 changed from Supply to Analog I/O 2) Pin VSUB added to Pin Descriptions (page 5) 3) Comments added for parameter `Total power dissipation' in Absolute Maximum Ratings (page 7) 4) Updated TAMB, ILEAK, RPD, IRA, ILP, VRFI, VRFI_LP, VPOR, VAR, TOSU in Electrical Characteristics (page 8) 2.2 July 15, 2009 Maks Sep 08, 2009 Mark 2.3 Oct 09, 2009 Maks Note: Typos may not be explicitly mentioned under revision history. www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 46 - 47 AS3910 Data Sheet - O r d e r i n g I n f o r m a t i o n 10 Ordering Information The devices are available as the standard products shown in Table 38. Table 38. Ordering Information Ordering Code AS3910-BQFP Description HF RFID Reader IC Delivery Form Tape & Reel in dry pack Package 32-pin QFN (5x5mm) Note: All products are RoHS compliant and Pb-free. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect For further information and requests, please contact us: RFID@austriamicrosystems.com or find your local distributor at http://www.austriamicrosystems.com/distributor Copyrights Copyright (c) 1997-2009, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered (R). All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered trademarks of their respective companies. Disclaimer Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by austriamicrosystems AG is believed to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to personal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriamicrosystems AG rendering of technical or other services. Contact Information Headquarters austriamicrosystems AG Tobelbaderstrasse 30 A-8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 RFID@austriamicrosystems.com For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact www.austriamicrosystems.com/HF_RFID_Reader/AS3910 Revision 2.3 47 - 47 |
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