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ASC7621
HARDWARE MONITOR WITH INTEGRATED FAN CONTROL
Preliminary Specification Product Description
The ASC7621 has a two wire digital interface compatible with SMBus 2.0. Using a 10-bit - ADC, the ASC7621 measures the temperature of two remote diode connected transistors as well as its own die. Support for Platform Environmental Control Interface (PECI) is included. Using temperature information from these four zones, an automatic fan speed control algorithm is employed to minimize acoustic impact while achieving recommended CPU temperature under varying operational loads. To set fan speed, the ASC7621 has three independent pulse width modulation (PWM) outputs that are controlled by one, or a combination of three, temperature zones. Both high- and low-frequency PWM ranges are supported. The ASC7621 also includes a digital filter that can be invoked to smooth temperature readings for better control of fan speed and minimum acoustic impact. The ASC7621 has tachometer inputs to measure fan speed on up to four fans. Limit and status registers for all measured values are included to alert the system host that any measurements are outside of programmed limits via status registers. System voltages of VCCP, 2.5V, 3.3V, 5.0V, and 12V motherboard power are monitored efficiently with internal scaling resistors.
PRODUCT SPECIFICATION
Measurement System
Temperature: * 0.25C resolution, 2C accuracy on remote diode * 0.25C resolution, 3C accuracy on local sensor * Temperature measurement range on remote sensor -55C to +125C using 2's complement coding. Voltage: * 10-bit Resolution, 2% (TUE) Fan Tachometer: * 16-bit count of 90kHz clock periods Limit alarms for all measured values
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Applications
* * Desktop Computers - Motherboards and Graphics Cards Microprocessor based equipment (e.g. Basestations, Routers, ATMs, Point of Sales)
Features
* * * * * * * * * * * * Supports PECI interface and monitors internal and remote thermal diodes 2-wire, SMBus 2.0 compliant, serial interface 10-bit -ADC Monitors VCCP, 2.5V, 3.3V, 5.0V, and 12V motherboard/processor supplies Programmable autonomous fan control based on temperature readings Noise filtering of temperature reading for fan speed control 0.25C digital temperature sensor resolution 3 PWM fan speed control outputs for 2-, 3- or 4wire fans and up to 4 fan tachometer inputs Enhanced measured temperature to Temperature Zone assignment. Provides high and low PWM frequency ranges 3 GPIO pins for custom use 24-Lead QSOP package
Connection Diagram
SMBDAT SMBCLK GND 3.3V GPIO2 GPIO1 PECI Vtt TACH3 PWM2 TACH1 TACH2
1 2 3 4 5 6 7 8 9 10 11 12
24 23 22 21 20
PWM1/ XTESTOUT VCCP 2.5V 12V 5V GPIO3 REMOTE 1+ REMOTE 1REMOTE 2+ REMOTE 2TACH4/ AddressSelect PWM3/ AddressEnable
ASC7621
19 18 17 16 15 14 13
Ordering Information
Part Number ASC7621QS24 Package 24-lead QSOP Temperature Range and Operating Voltage 0C to +120C, 3.3V Marking ASC7621 Ayww How Supplied 2500 units Tape & Reel
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ASC7621
Block Diagram
PECI Vtt
PECI INTERFACE
SERIAL BUS INTERFACE
SMBDAT SMBCLK
GPIO1 GPIO2 GPIO3 TACH1 TACH2 TACH3 TACH4/ Address Select 3.3V 5V 12V 2.5V VCCP REMOTE 1+ REMOTE 1REMOTE 2REMOTE 2+
GPIO REGISTER
VOLTAGE FAN SPEED TEMPERATURE, AND LIMIT VALUE REGISTERS
FAN SPEED COUNTER STEPPING AND DEVICE ID REGISTERS
LIMIT COMPARATORS
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
STATUS REGISTERS ADDRESS POINTER REGISTERS CONFIGURATION REGISTERS SPIKE SMOOTHING FAN TMIN/TRANGE/ HYST REGISTERS FAN CHARACTERISTICS FAN SPEED CONFIG REGISTERS FAN PWM CONTROL & PWM VALUE REGISTERS PWM3/ AddressEnable PWM2
INPUT ATTENUATORS, EXTERNAL DIODE SIGNAL CONDITIONING, AND ANALOG MULTIPLEXER
PWM1
10-bit
-ADC
INTERNAL TEMP SENSOR
BANDGAP REFERENCE
Figure 1 Block Diagram
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ASC7621
Pin Descriptions
Symbol SMBus SMBDAT SMBCLK PECI Vtt Pin 1 2 7 8 Type Digital I/O (Open-Drain) Digital Input Digital I/O Analog Input Name and Function/Connection System Management Bus Data. Open-drain output. 5V tolerant, SMBus 2.0 compliant. System Management Bus Clock. Tied to Open-drain output. 5V tolerant, SMBus 2.0 compliant. Platform Environmental Control Interface (PECI). PECI 1.0 compliant, CPU digital thermometer input PECI reference voltage. +3.3V pin. Can be powered by +3.3V Standby power if monitoring in low power states is required. This pin should be bypassed with a 0.1F capacitor in parallel with 100pF. A bulk capacitance of approximately 10F needs to be in near vicinity of the ASC7621. Ground for all analog and digital circuitry. Analog Input for +5V monitoring. Analog Input for +12V monitoring. Analog Input for +2.5V monitoring.. Analog Input for VCCP (processor voltage) monitoring. Positive input (current source) from the first remote thermal diode Serves as the positive input into the A/D. Connected to THERMDA pin of Pentium processor. Negative input (current sink) from the first remote thermal diode Serves as the negative input into the A/D. Connected to THERMDC pin of Pentium processor. Positive input (current source) from the second remote thermal diode Serves as the positive input into the A/D. Connected to the base of a diode connected MMBT3904 NPN transistor. Negative input (current sink) from the second remote thermal diode Serves as the negative input into the A/D. Connected to the emitter of a diode connected MMBT3904 NPN transistor. Input for monitoring tachometer output of fan 1. Input for monitoring tachometer output of fan 2. Input for monitoring tachometer output of fan 3. During power-up, if held low through a 10K resistor, SMBus address may be selected based on the state of TACH4 pin. Input for monitoring tachometer output of fan 4. If in Address Select Mode, determines the SMBus address of ASC7621. Fan speed control 1. When in XOR tree test mode, functions as XOR Tree output. Fan speed control 2. Fan speed control 3. Pull to ground at power on to enable Address Select Mode (Address Select pin controls SMBus address of the device).
Power
PECI
3.3V
4
POWER
Preliminary Specification - Subject to change without notice
GND 5V Voltage Inputs 12V 2.5V VCCP Remote 1+
3 20 21 22 23 18
GROUND Analog Input Analog Input Analog Input Analog Input Remote Thermal Diode Positive Input Remote Thermal Diode Negative Input Remote Thermal Diode Positive Output Remote Thermal Diode Negative Input Digital Input Digital Input Digital Input
Preliminary Specification - Subject to change without notice
Remote 1Remote
17
Remote 2+
16
Remote 2TACH1 Fan Tachometer Inputs TACH2 TACH3
15 11 12 9
TACH4/AddressSelect PWM1/XTESTOUT
14 24 10 13
Digital Input Digital OpenDrain Output Digital OpenDrain Output Digital OpenDrain Output
Fan Control
PWM2
PWM3/Address Enable
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ASC7621
Symbol GPIO1 GPIO GPIO2 GPIO3 Pin 6 5 19 Type Digital I/O Digital I/O Digital I/O Name and Function/Connection Alert Out / Zone # THERM Out. Default is GPIO input Alert Out / Zone # THERM Out. Default is GPIO input Alert Out / Zone # THERM Out. Default is GPIO input
Absolute Maximum Ratings1
Parameter Supply Voltage, VDD Voltage on Any Digital Input or Output Pin other than PWM Outputs Voltage on PWM Outputs Rating 3.6V -0.3V to VDD +0.3V -0.3V to 5.5V -0.5V to 16V -0.5V to 6.5V -0.5V to (VDD + 0.50V) -0.5V to 6.0V 1mA 5mA 20mA See (Note 3) -65C to +150C 4000 V 250 V 2000V
Operating Ratings1
Parameter ASC7621 Operating Temperature Range, Ambient Temperature, TMIN to TMAX Remote Diode Temperature Range Supply Voltage (3.3V nominal) VIN Voltage Range +12V VIN +5V VIN +3.3V VIN VCCP and All Other Inputs Typical Supply Current -0.05V to 16V -0.05V to 6.5V 3.0V to 4.4V -0.05V to VDD + 0.05V 1.8mA Rating 0C TA +120C -55C TD +125C +3.0V to +3.6V
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Voltage on 12V Analog Input Voltage on 5V Analog Input Voltage on Remote 1 +, Remote 2 + Voltage on Other Analog Inputs Current on Remote 1 -, Remote 2 Input Current on Any Pin Package Input Current2 Package Dissipation at TA = 25C Storage Temperature Human Body Model ESD4 Machine Model Charged Device Model
Notes:
2
1. Absolute maximum ratings are limits beyond which operation may cause permanent damage to the device. These are stress ratings only; functional operation at or above these limits is not implied. 2. When the input voltage (VIN) at any pin exceeds the power supplies (VIN < GND or VIN > VDD), the current at that pin should be limited to 5mA. The 20mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5mA to four. Parasitic components and/or ESD protection circuitry are present on the ASC7621 pins. Care should be taken not to forward bias the parasitic diode present on pins D+ and D-. Doing so by more than 50mV may corrupt temperature measurements.
3. Thermal resistance junction-to-ambient when
attached to a double-sided printed circuit board with 1oz. foil is 115C/W 4. Human Body Model: 100pF capacitor discharged through a 1.5k resistor into each pin. Machine Model: 200pF capacitor discharged directly into each pin. Charged-Device Model is per JESD22C101C.
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ASC7621
DC Electrical Characteristics5
The following specifications apply for VDD = 3.0V to 3.6V, and all analog input source impedance Rs = 50 unless otherwise specified in conditions. Boldface limits apply for TA = TJ over TMIN to TMAX; all other limits TA = TJ = 25C. TA is the ambient temperature of the ASC7621; TJ is the junction temperature of ASC7621; TD is the remote thermal diode junction temperature. Specifications subject to change without notice Parameter POWER SUPPLY CHARACTERISTICS Supply Current Converting, Interface and Fans Inactive, Peak Current Converting, Interface and Fans inactive, Average Current 1.6 1.8 0.5 2.8 3.5 mA(max) mA V Conditions Min Typ Max Units
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Power-On Reset Threshold Voltage TEMPERATURE TO DIGITAL CONVERTER CHARACTERISTICS Resolution 0C T A +100C, 0CTD +100C, 3VVDD3.6V 0C T A +120C, -55CTD +125C, 3VVDD3.6V 0C T A +120C, 3V V D D 3.6V IDS High Level Low Level
0.25 10 2
C Bits C
Remote Sensor Accuracy
6
3 1 96 6 16 3
C C A(max) A
Temperature Accuracy using 7 Internal Diode External Diode Current Source External Diode Current Ratio
ANALOG TO DIGITAL CONVERTER CHARACTERISTICS Total Unadjusted Error8 Differential Non-linearity Power Supply Sensitivity Total Monitoring Cycle Time9 Input Resistance, all analog inputs DIGITAL OUTPUT: PWM1, PWM2, PWM3, XTESTOUT Logic Low Sink Current Logic Low Level Logic Low Output Voltage High Level Output Current Logic Input High Voltage Logic Input Low Voltage Logic Input Hysteresis Voltage DIGITAL INPUTS: ALL Logic Input High Voltage
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TUE DNL All Voltage and Temperature readings 140 1 1 200 210
2
%(max) LSB %/V
250 400
ms (max) k
IOL VOL VOL IOH VIH VIL VHYST VIH
VOL = 0.4V IOUT = +8mA IOUT = +4mA VOUT = V+
8 0.4 0.4 0.1 2.1 0.8 300 2.1 10
mA (min) V (max) V (max) A(max) V (min) V (max) mV V (min)
October 2006 - 70A06010
SMBUS OPEN-DRAIN OUTPUT: SMBDAT
SMBUS INPUTS: SMBCLK, SMBDAT
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ASC7621
Parameter Logic Input Low Voltage Logic Input Threshold Voltage Logic High Input Current Logic Low Input Current Digital Input Capacitance VIL VTH IIH IIL CIN VIN = V+ VIN = GND 1.5 0.005 -0.005 20 10 -10 Conditions Min Typ Max 0.8 Units V (max) V A(max) A(max) pF
AC Electrical Characteristics
The following specifications apply for VDD = 3.0V to 3.6V unless otherwise specified in conditions. Boldface limits apply for TA = TJ over TMIN to TMAX; all other limits TA = TJ = 25C. Parameter TACHOMETER Conditions Min Typ Max Units
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Fan Full-Scale Count Fan Counter Clock Frequency Fan Count Conversion Time FAN PWM OUTPUT Low-Frequency Range Frequency Range High-Frequency Range Duty-Cycle Range Duty-Cycle Resolution (8-bits) Spin-Up Time Interval Range 0.3906 0 4000 10 94 23 30 0.3 90
65535 1.0
(max) kHz sec(max) Hz Hz kHz kHz
0 to 100
%(max) %/count ms ms
Logic Electrical Characteristics
(TA = 25 C, VDD = 3.3V unless otherwise noted) Parameter Input Voltage Logic High Input Voltage Logic Low Input Leakage Current SMBus Output Sink Current SMBus Logic Input Current Output Leakage Current Output Transition Time Input Capacitance Symbol VIH VIL IIN IOL IIH, IIL IOH tF CIN VOH = VDD = 5.5V CL= 400pF, IOL = -3mA All Digital Inputs Conditions 3V V D D 3.6V 3V V D D 3.6V VIN = 0V or 5.5V, 0C T A +125C TA = 25 C, VOL = 0.6V 6 -1 0.1 +1 1 250 5 Min 2.1 0.8 1.0 Typ Max Units V V A mA A A ns pF
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ASC7621
Serial Port Timing
(TA = 25 C, VDD = 3.3V unless otherwise noted, Guaranteed by design, not production tested) Parameter SCL Operating Frequency SCL Clock Transition Time SCL Clock Low Period SCL Clock High Period Bus free time between a Stop and a new Start Condition Data in Set-Up to SCL High Data Out Stable after SCL Low SCL Low Set-up to SDA Low (Repeated Start Condition) SCL High Hold after SDA Low (Start Condition) Symbol fSCL tT:LH , tT:HL tLOW tHIGH tBUF tSU:DAT tHD:DAT tSU:STA tHD:STA tSU:STO tPOR tTIMEOUT 25 1.3 0.6 1.3 100 300 600 600 600 500 35 50 Min Typ Max 400 300 Units kHz ns s s s ns ns ns ns ns ms ms
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
SDA High after SCL High (Stop Condition) Time in which ASC7621 must be operational after a power-on reset SMBus Time-out before device communication interface reset10
SCL
tHD:STA tSU:DAT
tSU:STA tSU:STO
SDA
tBUF tLOW tHIGH tT:LH 90 10 tT:HL 90 10
SCL SDA
Data Out Notes (cont'd):
tHD:DAT
5. These specifications are guaranteed only for the test conditions listed. 6. The accuracy of the ASC7621 is guaranteed when using the thermal diode of Intel Pentium 4, 65nm processors or any thermal diode with a non-ideality of 1.009 and series resistance of 4.52. When using a 2N3904 type transistor or an CPU with a different non-ideality the error band will be typically shifted depending on transistor diode or CPU characteristics. See applications section for details. 7. Accuracy (expressed in C) = Difference between the ASC7621 reported output temperature and the temperature being measured. Local temperature accuracy does not include the effects of self-heating. The rise in temperature due to self-heating is the product of the internal power dissipation of the ASC7621 and the thermal resistance. See (Note 3) for the thermal resistance to be used in the self-heating calculation. 8. TUE, total unadjusted error, includes ADC gain, offset, linearity and reference errors. TUE is defined as the "actual Vin" to achieve a given code transition minus the "theoretical Vin " for the same code. Therefore, a positive error indicates that the input voltage is greater than the theoretical input voltage for a given code. If the theoretical input voltage was applied to an ASC7621 that has positive error, the ASC7621's reading would be less than the theoretical. 9. This specification is provided only to indicate how often temperature and voltage data is updated. The ASC7621 can be read at any time without regard to conversion state (and will yield last conversion result). 10. Holding the SMBCLK line low for a time interval greater than tTIMEOUT will reset the ASC7621's SMBus state machine, therefore setting the SMBDAT pin to a high impedance state.
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ASC7621
Control Communication
SMBus
The ASC7621 is compatible with devices that are compliant to the SMBus 2.0 specifications. More information on this bus can be found at http://www.smbus.org/. Compatibility of SMBus2.0 to other buses is discussed in the SMBus 2.0 specification.
Slave Address
ASC7621 is designed to be used primarily in desktop systems that require only one monitoring device. If only one ASC7621 is used on the motherboard, the designer should be sure that the AddressEnable /PWM3 pin is High during the first SMBus communication addressing the ASC7621.
AddressEnable /PWM3 is an open drain I/O pin that at
General Operation
Writing to and reading from the ASC7621 registers is accomplished via the SMBus-compatible two-wire serial interface. SMBus protocol requires that one device on the bus initiate and control all read and write operations. This device is called the "master" device. The master device also generates the SCL signal that is the clock signal for all other devices on the bus. All other devices on the bus are called "slave" devices. The ASC7621 is a slave device. Both the master and slave devices can send and receive data on the bus. During SMBus operations, one data bit is transmitted per clock cycle. All SMBus operations follow a repeating nine clock-cycle pattern that consists of eight bits (one byte) of transmitted data followed by an acknowledge (ACK) or not acknowledge (NACK) from the receiving device. Note that there are no unused clock cycles during any operation-- therefore there must be no breaks in the stream of data and ACKs / NACKs during data transfers. For most operations, SMBus protocol requires the SDA line to remain stable (unmoving) whenever SCL is high -- i.e. any transitions on the SDA line can only occur when SCL is low. The exceptions to this rule are when the master device issues a start or stop condition. Note that the slave device cannot issue a start or stop condition.
power-on defaults to the input state of AddressEnable . A maximum of 10k pull-up resistance on
AddressEnable /PWM3 is required to assure that the SMBus address of the device will be locked at 010 1110b, which is the default address of the ASC7621.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
During the first SMBus communication TACH4 and PWM3 can be used to change the SMBus address of the ASC7621 to 0101101b or 0101100b. ASC7621 address selection procedure: A 10k pull-down resistor to ground on the
AddressEnable /PWM3 pin is required. Upon power up, the ASC7621 will be placed into AddressEnable mode and assign itself on SMBus address according to the state of the Address Select input. The ASC7621 will latch the address during the first valid SMBus transaction in which the first five bits of the targeted address match those of the ASC7621 address, 0 1011b. This feature eliminates the possibility of a glitch on the SMBus interfering with
address selection. When the AddressEnable /PWM3 pin is not used to change the SMBus address of the ASC7621, it will remain in a high state until the first communication with the ASC7621. After the first SMBus transaction is completed PWM3 and TACH4 will return to normal operation. Address Select Board Implementation Both pins pulled to ground through a 10 k resistor Address Select pulled to 3.3V and
AddressEnable pulled to GND through a 10 k resistor AddressEnable pulled to 3.3V through a 10 k resistor
SMBus Definitions
The following are definitions for some general SMBus terms: Start Condition: This condition occurs when the SDA line transitions from high to low while SCL is high. The master device uses this condition to indicate that a data transfer is about to begin. Stop Condition: This condition occurs when the SDA line transitions from low to high while SCL is high. The master device uses this condition to signal the end of a data transfer. Acknowledge and Not Acknowledge: When data are transferred to the slave device it sends an "acknowledge" (ACK) after receiving each byte. The receiving device sends an ACK by pulling SDA low for one clock. Following the last byte, a master device sends a "not acknowledge" (NACK) followed by a stop condition. A NACK is indicated by forcing SDA high during the clock after the last byte. Address Enable 0 SMBus Address Binary Hex 010 1100 2Ch
0
0
1
010 1101
2Dh
1
X
010 1110
2Eh
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ASC7621
In this way, up to three ASC7621 devices can exist on a SMBus at any time. Multiple ASC7621 devices can be used to monitor additional processors in the temperature zones. When using the non-default addresses, additional circuitry will be required if Tach4 and PWM3 require to function correctly. Such circuitry could consist of GPIO pins from a micro-controller. During the first communication the micro-controller would drive the
AddressEnable and Address Select pins to the proper state for the required address. After the first SMBus communication the micro-controller would drive its pins into Tri-State allowing TACH4 and PWM3 to operate correctly.
Writing to Registers
All writes must start with a pointer set as described previously, even if the pointer is already pointing to the desired register. The sequence is described in Figure 2. Immediately following the pointer set, the master must begin transmitting the data to be written. After transmitting each byte of data, the master must release the SDA line for one clock to allow the ASC7621 to acknowledge receiving the byte. The write operation should be terminated by a stop condition from the master.
Reading from Registers
Preliminary Specification - Subject to change without notice
Writing to and Reading from the ASC7621
All read and write operations must begin with a start condition generated by the master device. After the start condition, the master device must immediately send a slave address (7-bits) followed by a R/ W bit. If the slave address matches the address of the ASC7621, it sends an ACK by pulling the SDA line low for one clock. Read or write operations may contain one- or two-bytes. See Figures 2 through 6 for timing diagrams for all ASC7621 operations.
To read from a register other than the one currently being pointed to by the address pointer register, a pointer set sequence to the desired register must be done as described previously. Immediately following the pointer set, the master must perform a repeat start condition that indicates to the ASC7621 that a read is about to occur. It is important to note that if the repeat start condition does not occur, the ASC7621 will assume that a write is taking place, and the selected register will be overwritten by the upcoming data on the data bus. The read sequence is described in Figure 4. After the start condition, the master must again send the device address and read/write bit. This time the R/ W bit must be set to 1 to indicate a read. The rest of the read cycle is the same as described in the previous paragraph for reading from a preset pointer location. If the pointer is already pointing to the desired register, the master can read from that register by setting the R/ W bit (following the slave address) to a 1. After sending an ACK, the ASC7621 will begin transmitting data during the following clock cycle. After receiving the 8 data bits, the master device should respond with a NACK followed by a stop condition. If the master is reset while the ASC7621 is in the process of being read, the master should perform an SMBus reset. This is done by holding the clock low for more than 35ms, allowing all SMBus devices to be reset. This follows the SMBus 2.0 specification of 25-35ms. When the ASC7621 detects an SMBus reset, it will prepare to accept a new start sequence and resume communication from a known state.
Preliminary Specification - Subject to change without notice
Setting the Register Address Pointer
For all operations, the address pointer stored in the address pointer register must be pointing to the register address that is going to be written to or read from. This register's content is automatically set to the value of the first byte following the R/ W bit being set to 0. After the ASC7621 sends an ACK in response to receiving the address and R/ W bit, the master device must transmit an appropriate 8-bit address pointer value as explained in the Registers section of this data sheet. The ASC7621 will send an ACK after receiving the new pointer data. The register address pointer set operation is illustrated in Figure 2. If the address pointer is not a valid address the ASC7621 will internally terminate the operation. Also recall that the address register retains the current address pointer value between operations. Therefore, once a register is being pointed to, subsequent read operations do not require another Address Pointer set cycle.
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ASC7621
Note: The following figures assume that Device Address 2Ch has been chosen by the user via address selection.
1 SCL SDA S 0 1 0 1 1 0 0 R/W A A7 A6 A5 A4 A3 A2 A1 A0 A 9 1 9
Start
SMBus Device Address Byte (2Ch)
ACK from ASC7621
Register Address Byte
ACK from ASC7621
Stop By Master
Figure 2 Register Address Pointer Set
1 SCL
9
1
9
1
9
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
SDA
S
0
1
0
1
1
0
0
R/W
A
A7
A6
A5
A4
A3
A2
A1
A0
A
D7
D6
D5
D4
D3
D2
D1
D0
A
Start
SMBus Device Address Byte (2Ch)
ACK from ASC7621
Register Address Byte
ACK from ASC7621
Register Data Byte
ACK from ASC7621
Stop by Master
Figure 3 Register Write
1
9
1
9
Register Address Pointer Set + (Figure 2.) without stop by Master
S
0
1
0
1
1
0
0
R/W
A
D7
D6
D5
D4
D3
D2
D1
D0
N
Re-start
ACK
from SMBus Device Address Byte (2Ch) ASC7621
Register Data Byte
NACK from Master
Stop by Master
Figure 4 Register Read
1 SCL SDA S 0 1 0 1 1 0 0 R/W
9
1
9
A
D7
D6
D5
D4
D3
D2
D1
D0
N Stop by Master
Start
SMBus Device Address Byte (2Ch)
ACK from ASC7621
Register Data Byte
NACK from Master
Figure 5 Register Read When Read Address Already Set
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ASC7621
PECI
The ASC7621 is compatible with devices that are compliant with Intel's PECI 1.0 specifications. More information on this interface may be found in their PECI interface specifications. Temperatures sent over the PECI interface from the CPU are in Celsius degrees relative to the Thermal Control Circuit (TCC) temperature stored internally in the CPU and accessed only through BIOS. This is the temperature limit where internal measures are taken to reduce power dissipation. Fan speed control settings sent by the BIOS over the SMBus to registers in the ASC7621 are made using this relative temperature rather than the absolute readings of remote or on-chip diodes. PECI temperatures assigned to a Temperature Zone are reported over SMBus interface in Temperature Zone registers also will be in the range 0C to -127C. The format reported through Temperature Zone registers is re-aligned to agree with diode measurements. It is stored in two register locations in the following format with integer high byte and fractional low byte to be consistent with all other temperature reports: 2's Complement Representation High Byte Low Byte 0000 0000 .0000 0000 1111 1111 .0000 0000 1111 1011 .0000 0000 1110 0000 .0000 0000 1000 0001 .0000 0000
Temperature 0 C -1 C -5 C -32 C -127 C
Preliminary Specification - Subject to change without notice
As many as four CPU clients on the PECI bus are addressed in the range of 0x30 to 0x33. Currently, each address is a single-packaged device that may have up to two domains or CPU-measured digital temperatures.
Preliminary Specification - Subject to change without notice
Table 2 PECI Temperature Report Format PECI Errors
A specific set of temperature reading value encodings, well outside the operational range of 0C to -127C, are reserved to signal temperature sensor faults on the CPU to ASC7621 interface. These encodings are in the PECI temperature format as delivered by the CPU and are converted to the appropriate Interrupt Status Register 3 error bits described in the Interrupt Status register section below.
General Operation
The PECI host in ASC7621 performs the following functions: * Responds to SMBus configuration identifying the presence of PECI clients and the Thermal Zone associated with each client. * Reads the PECI temperature of the domain(s) of each client processor addressed. * Stores the highest result from each PECI address into Temperature Zone register associated to the measurement received from the client. (each address may be associated with any one Temperature Zone.) * Flags an error if no valid PECI temperature can be read. * Continuously monitors the state of the PECI interface for fault conditions.
PECI Temperature Format and Range
The PECI temperatures read from the processor will be in the range 0C to -127C where 0C is the hottest temperature and has the following format: Temperature 0 C -1 C -5 C -32 C -127 C 2's Complement Representation 0000 0000 00.00 0000 1111 1111 11.00 0000 1111 1110 11.00 0000 1111 1000 00.00 0000 1111 0000 01.00 0000
Table 1 Raw PECI Temperature Format
These readings are not accessible to the user but are filtered, re-formatted and assigned to a Temperature Zone. Filtered PECI Temperature readings are accessible by the user before they are assigned to a Temperature Zone by reading registers F6h through FDh. These readings follow the format described in Table 2. The
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ASC7621
Register Set
Register Address Register Name Bit 7 (MSB) Bit 0 (LSB) Default Value (hex)
N/A 00 00 36 36 36 36 X X X X X X
R/W
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
00h 02h 03h
R R/W R/W R/W R/W R/W R/W
Fan Zone Status Zone 1 & 2 Assignment Zone 3 & 4 Assignment Tach 1 Configuration Tach 2 Configuration Tach 3 Configuration Tach 4 Configuration PECI Extended Configuration Zone 1 Temperature (LS Byte) 3.3V (LS Byte) 5V (LS Byte) 2.5V (LS Byte) 12V (LS Byte) Zone 2 Temperature (LS Byte) Zone 3 Temperature (LS Byte) Zone 4 Temperature (LS Byte) Vccp (LS Byte) GPIO 1 Configuration GPIO 2 & 3 Configuration Remote 1 offset Remote 2 offset 2.5V (MS Byte) Vccp (MS Byte) 3.3 V (MS Byte) 5V (MS Byte) 12V (MS Byte) Zone 1 Temperature (MS Byte) Zone 2 Temperature (MS Byte) Zone 3 Temperature (MS Byte)
Fan 3 Zone # 1 RES RES
3-Wire Enable1 3-Wire Enable1 3-Wire Enable1 3-Wire Enable1
Fan 2 Zone # 1 Zone 1 Source 1 Zone 3 Source 1
Meas Blank1 Meas Blank1 Meas Blank1 Meas Blank1
Fan 1 Zone # 1 RES RES
Meas Dwell 1 Meas Dwell 1 Meas Dwell 1 Meas Dwell 1
0 2 2
3-Wire Enable0 3-Wire Enable0 3-Wire Enable0 3-Wire Enable0
0 0 0
Meas Blank 0 Meas Blank 0 Meas Blank 0 Meas Blank 0
0 2 2
Meas Dwell 0 Meas Dwell 0 Meas Dwell 0 Meas Dwell 0
RES Zone 2 Source 1 Zone 4 Source 1
Meas Duration 1 Meas Duration 1 Meas Duration 1 Meas Duration 1
RES
0 0
Meas Duration 0 Meas Duration 0 Meas Duration 0 Meas Duration 0
Lock
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
04h 05h 06h 07h
0Eh 10h 11h 12h 13h 14h 15h 16h 17h 18h 19h 1Ah 1Ch 1Dh 20h 21h 22h 23h 24h 25h 26h 27h
R/W R R R R R R R R R R/W R/W R/W R/W R R R R R R R R
Four Domain Enable 1 1 1 1 1 1 1 1 1 RES GPIO 2 bit 7 7 7 7 7 7 7 9 9 9
Diode Filter2 0 0 0 0 0 0 0 0 0 RES
Diode Filter1 X X X X X X X X X 1
Diode Filter0 X X X X X X X X X 0 0 4 4 4 4 4 4 4 6 6 6
Proc 3 Enable X X X X X X X X X GPIO 1 bit GPIO 3 bit 3 3 3 3 3 3 3 5 5 5
Proc 2 Enable X X X X X X X X X 2 2 2 2 2 2 2 2 2 4 4 4
Proc 1 Enable X X X X X X X X X GPIO 1 Function 1 GPIO 3 Function 1 1 1 1 1 1 1 1 3 3 3
Proc 0 Enable X X X X X X X X X 0 0 0 0 0 0 0 0 0 2 2 2
21 N/A N/A N/A N/A N/A N/A N/A N/A N/A 00 00 00 00 N/A N/A N/A N/A N/A N/A N/A N/A
X
Alert Assignment GPIO 2 Function
X X X X
2 6 6 6 6 6 6 6 8 8 8
1 5 5 5 5 5 5 5 7 7 7
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ASC7621
Register Address Default Value (hex)
FF FF FF FF FF FF FF FF FF FF FF N/A 81h 00h 00h FF FF FF E0h C3h X X X X X X
R/W
Register Name
Tach 1 LS Byte Tach 1 MS Byte Tach 2 LS Byte Tach 2 MS Byte Tach 3 LS Byte Tach 3 MS Byte Tach 4 LS Byte Tach 4 MS Byte Fan 1 Current PWM Duty Fan 2 Current PWM Duty Fan 3 Current PWM Duty Zone 4 Temperature (MS Byte) Zone 4 Low Temp Zone 4 High Temp PECI Configuration Fan 1 Max Duty Cycle Fan 2 Max Duty Cycle Fan 3 Max Duty Cycle Zone 4 Fan Temp Limit Zone 4 Range, Spike Smoothing Zone 4 Absolute Temp Limit Company ID Version/ Stepping Ready/Lock/ Start/Override Interrupt Status Register 1 Interrupt Status Register 2 Interrupt Status Register 3
Bit 7 (MSB)
7 15 7 15 7 15 7 15 7 7 7 9 7 7 RES 7 7 7 7 RAN3
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
0 8 0 8 0 8 0 8 0 0 0 2 0 0 AVG0 0 0 0 0 ZN4-0
28h 29h 2Ah 2Bh 2Ch 2Dh
R R R R R R R R R/W R/W R/W R R/W R/W R/W R/W R/W R/W R/W R/W
6 14 6 14 6 14 6 14 6 6 6 8 6 6 RES 6 6 6 6 RAN2
5 13 5 13 5 13 5 13 5 5 5 7 5 5 RES 5 5 5 5 RAN1
4 12 4 12 4 12 4 12 4 4 4 6 4 4 LEG 4 4 4 4 RAN0
3 11 3 11 3 11 3 11 3 3 3 5 3 3 DOM 3 3 3 3 ZN4E
2 10 2 10 2 10 2 10 2 2 2 4 2 2 AVG2 2 2 2 2 ZN4-2
1 9 1 9 1 9 1 9 1 1 1 3 1 1 AVG1 1 1 1 1 ZN4-1
Preliminary Specification - Subject to change without notice
2Eh 2Fh 30h 31h 32h 33h 34h 35h 36h 38h 39h 3Ah 3Bh 3Ch
Lock
Preliminary Specification - Subject to change without notice
3Dh 3Eh 3Fh 40h 41h 42h 43h
R/W R R R/W R R R
7 7 VER3 RES ERR ERR2 ERR
6 6 VER2 RES ZN3 ERR1 RES
5 5 VER1 SAFE ZN2 FAN4 RES
4 4 VER0 PECI ZN1 FAN3 RES
3 3 4WIRE OVRID 5V FAN2 ALOVR
2 2 PECI READY 3.3V FAN1 COMM
1 1 STP1 LOCK VCCP ERR DATA
0 0 STP0 START 2.5V 12V ZN4
00h 61 6C 00 00 00 00h
X
X
2
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ASC7621
Register Address Default Value (hex)
00 FF 00 FF 00 FF 00 FF 00 FF 81 7F 81 7F 81 7F FF FF FF FF FF FF FF FF 62 62 62 C3 X X X X
R/W
Register Name
2.5V Low Limit 2.5V High Limit Vccp Low Limit Vccp High Limit 3.3V Low Limit 3.3V High Limit 5V Low Limit 5V High Limit 12V Low Limit 12V High Limit Zone 1 Low Temperature Zone 1 High Temperature Zone 2 Low Temperature Zone 2 High Temperature Zone 3 Low Temperature Zone 3 High Temperature Tach 1 Minimum LS Byte Tach 1 Minimum MS Byte Tach 2 Minimum LS Byte Tach 2 Minimum MS Byte Tach 3 Minimum LS Byte Tach 3 Minimum MS Byte Tach 4 Minimum LS Byte Tach 4 Minimum MS Byte Fan 1 Configuration Fan 2 Configuration Fan 3 Configuration Zone 1 Range/ Fan 1 Frequency
Bit 7 (MSB)
7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 15 7 15 7 15 7 15 ZON2 ZON2 ZON2 RAN3
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 8 0 8 0 8 SPIN0 SPIN0 SPIN0 FRQ0
44h 45h 46h 47h 48h 49h
R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 14 6 14 6 14 6 14 ZON1 ZON1 ZON1 RAN2
5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 13 5 13 5 13 5 13 ZON0 ZON0 ZON0 RAN1
4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 12 4 12 4 12 4 12 INV INV INV RAN0
3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 11 3 11 3 11 3 11 ALT ALT ALT HLFRQ
2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 10 2 10 2 10 2 10 SPIN2 SPIN2 SPIN2 FRQ2
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 9 1 9 1 9 1 9 SPIN1 SPIN1 SPIN1 FRQ1
Preliminary Specification - Subject to change without notice
4Ah 4Bh 4Ch 4Dh 4Eh 4Fh 50h 51h 52h 53h 54h 55h 56h 57h 58h 59h 5Ah 5Bh 5Ch 5Dh 5Eh 5Fh
Lock
Preliminary Specification - Subject to change without notice
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ASC7621
Register Address Default Value (hex)
C3
R/W
Register Name
Zone 2 Range/ Fan 2 Frequency Zone 3 Range/ Fan 3 Frequency Min/Off, Zone 1 Spike Smoothing Zone 2 / Zone 3 Spike Smoothing Fan 1 PWM Minimum Fan 2 PWM Minimum Fan 3 PWM Minimum Zone 1 Fan Temp Limit Zone 2 Fan Temp Limit Zone 3 Fan Temp Limit Zone 1 Temp Absolute Limit Zone 2 Temp Absolute Limit Zone 3 Temp Absolute Limit Zone 1, Zone 2 Hysteresis Zone 3, Zone 4 Hysteresis XOR Tree Enable Fan Spin-up Mode
Bit 7 (MSB)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
60h
R/W
RAN3
RAN2
RAN1
RAN0
HLFRQ
FRQ2
FRQ1
FRQ0
61h
R/W
RAN3
RAN2
RAN1
RAN0
HLFRQ
FRQ2
FRQ1
FRQ0
C3
62h
R/W
OFF3
OFF2
OFF1
RES
ZN1E
ZN1-2
ZN1-1
ZN1-0
00
63h
R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
ZN2E 7 7 7 7 7 7 7 7 7 H1-3 H3-3 RES Tach4 Disable
ZN2-2 6 6 6 6 6 6 6 6 6 H1-2 H3-2 RES Tach3/4 Disable
ZN2-1 5 5 5 5 5 5 5 5 5 H1-1 H3-1 RES Tach2 Disable
ZN2-0 4 4 4 4 4 4 4 4 4 H1-0 H3-0 RES Tach1 Disable
ZN3E 3 3 3 3 3 3 3 3 3 H2-3 H4-3 RES RES
ZN3-2 2 2 2 2 2 2 2 2 2 H2-2 H4-2 RES
PWM3SU
ZN3-1 1 1 1 1 1 1 1 1 1 H2-1 H4-1 RES
PWM2SU
ZN3-0 0 0 0 0 0 0 0 0 0 H2-0 H4-0 XEN
PWM1SU
00 80 80 80 5A 5A 5A 64 64 64 44 44 00 00
Lock
X X X X
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
64h 65h 66h 67h 68h 69h 6Ah 6Bh 6Ch 6Dh 6Eh 6Fh 75h
X X X X X X X X X X X X X
Notes:
1. 2. 3. Reserved bits will always return 0 when read, X-bits in readings may be ignored. When register 40h is locked, all bits are locked except 0 and 3 which remain user changeable. Two-byte or extended resolution temperature, voltage and tachometer values are protected from changing when only one of the bytes is read. The implementation of a data word latch involves the register pairs in the table below. When one of the address pairs is read, the mating data is latched at the same time. The next SMBus access MUST be the mating address or the latch will be released. This implementation allows that the data may be read in the order of LS-MS or MS-LS and the pair will remain coherent.
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ASC7621
MS-Byte Address (hex) 25 26 27 33 20 21 22 23 24 29 2B 2D 2F
LS-Byte Address (hex) 10 15 16 17 13 18 11 12 14 28 2A 2C 2E
Data Field Name Zone 1 Temperature Zone 2 Temperature Zone 3 Temperature Zone 4 Temperature 2.5V VCCP 3.3V 5V 12V Tach 1 Tach 2 Tach 3 Tach 4
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
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ASC7621
Temperature Measurement
Diode temperatures are measured with a precision Delta-VBE methodology converted to a digital temperature reading by a 10-bit sigma-delta converter. PECI interface to the CPU provide Digital Thermometer readings of substrate temperature. The measurement system provides a means for assigning any of the temperature inputs to a Temperature Zone. The user may set limits on these readings to be continuously monitored and alarm bits set when they are exceeded. Separately, the measurements are also delivered to the automatic fan control system to adjust fan speed. The following registers contain the readings from the internal and remote sensors.
Registers 25-10h, 26-15h and 27-0Eh: Temperature Zone Readings (10-Bit, 2's Complement Reporting)
Register Address
25h 10h
Read/ Write
R R R R R R R R
Register Name
Zone 1 Temperature (MS Byte) Zone 1 Temperature (LS Byte) Zone 2 Temperature (MS Byte) Zone 2 Temperature (LS Byte) Zone 3 Temperature (MS Byte) Zone 3 Temperature (LS Byte) Zone 4 Temperature (MS Byte) Zone 4 Temperature (LS Byte)
Bit 7 (MSB)
9 1 9 1 9 1 9 1
Bit 6
8 0 8 0 8 0 8 0
Bit 5
7 X 7 X 7 X 7 X
Bit 4
6 X 6 X 6 X 6 X
Bit 3
5 X 5 X 5 X 5 X
Bit 2
4 X 4 X 4 X 4 X
Bit 1
3 X 3 X 3 X 3 X
Bit 0 (LSB)
2 X 2 X 2 X 2 X
Default Value
N/A N/A
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
26h 15h 27h 16h 33h 17h
N/A N/A N/A N/A N/A N/A
The Temperature Zone registers reflect the current temperature of the internal and remote diodes or PECI CPU Digital Thermometers. Filtering is applied to all readings and this is described in the Spike & Smoothing Filter section below. Any temperature input may be assigned to any zone, according to the settings in the Zone Assignment Registers, [02h] and [03h]. The default assignment is as follows: Zone 1 Temperature register reports the temperature measured by the thermal diode connected to the Remote 1- and Remote 1+ pins if either: 1. 2. PECI monitoring is disabled (register [40h] bit 4=0) PECI monitoring is enabled but in legacy mode, (register [36h] bit 4, LEG = 0).
If PECI Monitoring is enabled (register [40h] bit 4=1) AND legacy mode is LEG = legacy mode (register [36h] bit 4, LEG = 1), the register reports the highest Digital Thermometer reading by the processor. Zone 2 Temperature register reports the temperature measured by the internal (junction) temperature sensor. Zone 3 Temperature register reports the temperature measured by the thermal diode connected to the second set of Remote 2- and Remote 2+ pins. Zone 4 reports temperatures as follows: 1. By default and if PECI temperature is disabled (register [36h] bit 4, LEG = 0) the Zone 4 register is not used. In this case, special temperature value of 80h will be reported to indicate that no temperature is available. If this zone is associated with any fan PWM controller(s), this will result in these controller(s) being overridden to 100% duty cycle. No error bits will be set in the Interrupt Status Registers. If PECI Monitoring is enabled [40h] bit 4=1) AND legacy mode is in standard mode (register [36h] bit 4, LEG = 0), the register will report the highest Digital Thermometer reading by the processor. Temperatures are represented as 10-bit, 2's complement, signed numbers, in degrees Celsius, as shown below in Table 3. If PECI Monitoring is enabled [40h] bit 4=1) AND legacy mode is in legacy mode (register [36h] bit 4, LEG = 1), the register will report the temperature measured by the thermal diode connected to the Remote 1- and Remote 1+ pins.
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2. 3. 4.
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ASC7621
A remote diode temperature reading register will return a value of 8000h if the remote diode pins are not used by the board designer or is not functioning properly. This reading will cause the zone limit bits (bits 4 and 6) in the Interrupt Status Register (41h) and the remote diode fault status bit (bits 6 and 7) in the Interrupt Status Register 2 (42h) to be set. These registers are read-only - a write to these registers has no effect. Digital Output (2's Complement) Temperature +125C +100C +50C +25C +10C +1.75C
High Byte 10-Bit Resolution Low Byte Ignore
0111 0110 0011 0001 0000 0000 0000 0000 1111 1100
1101 0100 0010 1001 1010 0001 0000 0000 1110 1001
.00 .00 .00 .00 .00 .11 .01 .00 .01 .00
XX XX XX XX XX XX XX XX XX XX
XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
+0.25C 0C -1.75C -55C
Table 3 Relationship between Temperature and 2's Complement Digital Output, -55C to +125C
Digital Output (2's Complement) Temperature 0C -0.015625C -0.03125C -0.0625C -0.125C -0.25C -0.5C -1.0C -1.75C -2.0C -25.0C -100C -127C
High Byte 10-Bit Resolution Low Byte Ignore
0000 1111 1111 1111 1111 1111 1111 1111 1111 1111 1110 1001 1000
0000 1111 1111 1111 1111 1111 1111 1111 1110 1110 0111 1100 0001
.0000 .1111 .1111 .1111 .1110 .1100 .1000 .0000 .0100 0000 0000 0000 0000
00 11 10 00 00 00 00 00 00 00 00 00 00
XX XX XX XX XX XX XX XX XX XX XX XX XX
Table 4 PECI Temperature Format
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ASC7621
Temperature Measurement Configuration
Registers 02h and 03h: Zone Assignments
Register Address R/W Register Name Bit 7 (MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB) Default Value Lock
02h 03h
R/W R/W
Zone 1 & 2 Assignment Zone 3 & 4 Assignment
RES RES
Zone 1 Source 6 6 5 Zone 3 Source 5 4 4
RES RES
Zone 2 Source 2 2 1 Zone 4 Source 1 0 0
00 00
X X
Preliminary Specification - Subject to change without notice
The temperature measurement system has access to more temperature measuring devices than there are Temperature Zones that may be reported to the user or used to control a fan. It is allowed that any data input may be associated with any single Temperature Zone. However, if an attempt is made to assign a data source to more than one Temperature Zone report, the lowest order will be assigned and the other assignment will be ignored. Do not attempt to assign a data source to more than one Temperature Zone or multiple data sources to the same Temperature Zone. This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
Preliminary Specification - Subject to change without notice
Bit
Name
Value 000 001 010
Zone 1 & 2 Assignment [02h]
Data Source Internal Temperature Remote 1 Temperature Remote 2 Temperature Internal Temperature PECI Processor Temperature 0 PECI Processor Temperature 1 PECI Processor Temperature 2 PECI Processor Temperature 3 Reserved Value 000 001 Data Source LEG = 0, Remote 1 Temperature LEG = 1, PECI Processor Temperature 0 Remote 1 Temperature Remote 2 Temperature Internal Temperature PECI Processor Temperature 0 PECI Processor Temperature 1 PECI Processor Temperature 2 PECI Processor Temperature 3 Reserved
2:0
Zone 2 Source
011 100 101 110 111
3
Reserved
6:4
Zone 1 Source
010 011 100 101 110 111
7
Reserved
Table 5 Zone 1 & 2 Temperature Reading Assignment [02h]
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ASC7621
Bit
Name
Value 000 001
Zone 3 & 4 Assignment [03h]
Data Source LEG = 0, PECI Processor Temperature 0 LEG = 1, Remote 1 Temperature Remote 1 Temperature Remote 2 Temperature Internal Temperature PECI Processor Temperature 0 PECI Processor Temperature 1 PECI Processor Temperature 2
2:0
Zone 4 Source
010 011 100 101 110 111
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
PECI Processor Temperature 3 Reserved
3
Reserved Value 000 001 010
Data Source Remote 2 Temperature Remote 1 Temperature Remote 2 Temperature Internal Temperature PECI Processor Temperature 0 PECI Processor Temperature 1 PECI Processor Temperature 2 PECI Processor Temperature 3 Reserved
6:4
Zone 3 Source
011 100 101 110 111
7
Reserved
Table 6 Zone 3 & 4 Temperature Reading Assignment [03h]
Bit
3:0 4 5 6 7
Name
Reserved PECI OneShot Enable Reserved Run/Stop Reserved
Default
0 0 0 0 0 Reserved
Description
0 = Disable PECI One Shot, 1 = Enable PECI One-Shot Reserved Measurement system run(default) or stop (set to 1), places ASC7621 in a low-power or standby mode. Reserved
Table 7 Configuration Register [09h] bits
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ASC7621
Register 36h: PECI Configuration
Register Address
36h
Read/ Write
R/W
Register Name
PECI Configuration
Bit 7 (MSB)
RES
Bit 6
RES
Bit 5
RES
Bit 4
LEG
Bit 3
DOM
Bit 2
AVG2
Bit 1
AVG1
Bit 0 (LSB)
AVG0
Default Value
00h
Lock
X
This register establishes legacy diode register assignment condition of Temperature Zones 1 and 4, LEG; the number of domains per client, DOM; and PECI input filter coefficients, AVG[2:0]. This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
Bit
Field
Value 000 (default) 001 010 011 100 101 110 111 0 (default) 1 0 (default) (Standard Mode) 1 (Legacy Mode) 0
Function 0 Sec. (no Smoothing) 0.25 Sec. 0.5 Sec. 1.0 Sec. 2.0 Sec. 4.0 Sec. 8.0 Sec. 0 Sec. Processor contains a single domain (0) Processor contains two domains (0,1) Remote Diode 1 reading is associated with Temperature Zone 1, PECI is associated with Zone 4 PECI is associated with Temperature Zone 1, Remote Diode 1 is associated with Zone 4 Reserved
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
2:0
AVG (PECI Input Filter)
3
DOM
4 5:7
LEG Reserved
Table 8 PECI Configuration [36h] Register 0Eh: PECI Extended Configuration
Register Address
0Eh
Read/ Write
R/W
Register Name
PECI Extended Configuration
Bit 7 (MSB)
Four Domain Enable
Bit 6
Diode Filter2
Bit 5
Diode Filter1
Bit 4
Diode Filter0
Bit 3
Proc 3 Enable
Bit 2
Proc 2 Enable
Bit 1
Proc 1 Enable
Bit 0 (LSB)
Proc 0 Enable
Default Value
21
Lock
X
This register establishes the number of domains per PECI address and enables up to four PECI clients to be polled for temperatures. If bit-0 through bit-3 are reset, PECI will not be available. In addition, a remote diode noise filter may be tuned for optimum performance when excessive noise is present in remote diode readings. This is a low-pass filter that also eliminates single sample spikes before they are stored in Temperature Zone registers. Filter algorithm is described in the section on Spike Smoothing registers 62h, 63h and 3Ch. Times indicated in Table 9 show the approximate filter response time to a step function in temperature diode measurement as applied to the assigned Temperature Zone reading. This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
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ASC7621
Bit 0 1 2 3 Field Processor 0 Enable Processor 1 Enable Processor 2 Enable Processor 3 Enable Value 0 1 (default) 0 (default) 1 0 (default) 1 0 (default) 1 000 001 010 (default) 011 100 101 110 111 0 (default) 1 Function PECI Processor 0 disabled PECI Processor 0 enabled PECI Processor 1 disabled PECI Processor 1 enabled PECI Processor 2 disabled PECI Processor 2 enabled PECI Processor 3 disabled PECI Processor 3 enabled 0.25 Sec. 1.1 Sec. 2.4 Sec. 3.4 Sec. 5.0 Sec. 6.8 Sec. 10.2 Sec. 16.4 Sec. 1 or 2 Domains for enabled processors 3 or 4 Domains for enabled processors
6:4
Diode Filter
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
7
Four Domain Enable
Table 9 PECI Extended Configuration [0Eh] Register 1Ch and 1Dh: Remote Offset Registers
Register Address
1Ch 1Dh
Read/ Write
R/W R/W
Register Name
Remote 1 offset Remote 2 offset
Bit 7 (MSB)
7 7
Bit 6
6 6
Bit 5
5 5
Bit 4
4 4
Bit 3
3 3
Bit 2
2 2
Bit 1
1 1
Bit 0 (LSB)
0 0
Default Value
00 00
This register provides a means to offset readings from remote diodes to compensate for errors due to system noise or series resistance. It may also be used to compensate for a difference in temperature between the remote diode and the temperature of interest once that is characterized by the user. It is in 2's Complement format with 0.25 degree resolution. The range is -32 to +31.75C and is described in Table 10: Offset Temperature +31.75C +31C +1C +0.5C +0.25C 0C -0.25C -1C -31C -31.75C -32C
Value[7:0]
0111 0111 0000 0000 0000 0000 1111 1111 1000 1000 1000
11.11 11.10 01.00 00.10 00.01 00.00 11.11 11.00 01.00 00.01 00.00
Table 10 Offset Temperature Data Format
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ASC7621
Voltage Measurement and Limits
Register 20-24h: Voltage Reading
Register Address
20h 13h 21h 18h 22h 11h 23h 12h 24h
Read/ Write
R R R R R R R R R R
Register Name
2.5V (MS Byte) 2.5V (LS Byte) VCCP (MS Byte) VCCP (LS Byte) 3.3V (MS Byte) 3.3V (LS Byte) 5V (MS Byte) 5V (LS Byte) 12V (MS Byte) 12V (LS Byte)
Bit 7 (MSB)
9 1 9 1 9 1 9 1 9 1
Bit 6
8 0 8 0 8 0 8 0 8 0
Bit 5
7 X 7 X 7 X 7 X 7 X
Bit 4
6 X 6 X 6 X 6 X 6 X
Bit 3
5 X 5 X 5 X 5 X 5 X
Bit 2
4 X 4 X 4 X 4 X 4 X
Bit 1
3 X 3 X 3 X 3 X 3 X
Bit 0 (LSB)
2 X 2 X 2 X 2 X 2 X
Default Value
N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
14h
The Register Names define the typical input voltage at which the reading is 3/4 full scale or C000h. High byte readings are 8bits with an LS bit value of Nominal divided by 192 and 2-bits in the high-order portion of the LS Byte having a value corresponding to 1/2 and 1/4 of that high byte LS bit value. Ignore the lower 6-bits of the LS Byte. The Voltage Reading registers are updated automatically by the ASC7621 at a minimum frequency of 4Hz and a typical frequency of 5 Hz. These registers are read only - a write to these registers has no effect.
Register 44-4Dh: Voltage Limit Registers
Register Address
44h 45h 46h 47h 48h 49h 4Ah 4Bh 4Ch 4Dh
Read/ Write
R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
Register Name
2.5V Low Limit 2.5V High Limit VCCP Low Limit VCCP High Limit 3.3V Low Limit 3.3V High Limit 5V Low Limit 5V High Limit 12V Low Limit 12V High Limit
Bit 7 (MSB)
7 7 7 7 7 7 7 7 7 7
Bit 6
6 6 6 6 6 6 6 6 6 6
Bit 5
5 5 5 5 5 5 5 5 5 5
Bit 4
4 4 4 4 4 4 4 4 4 4
Bit 3
3 3 3 3 3 3 3 3 3 3
Bit 2
2 2 2 2 2 2 2 2 2 2
Bit 1
1 1 1 1 1 1 1 1 1 1
Bit 0 (LSB)
0 0 0 0 0 0 0 0 0 0
Default Value
00h FFh 00h FFh 00h FFh 00h FFh 00h FFh
If a voltage input either exceeds the value set in the voltage high limit register or falls below the value set in the voltage low limit register, the corresponding bit will be set automatically by the ASC7621 in the interrupt status registers (41-42h). The binary value of the voltage limits are extended to 16-bits and compared with the two-bytes of the voltage reading. Voltages are presented in the registers at 3/4 of full-scale for the nominal voltage, meaning that at nominal voltage, each input will be C0h, as shown in Table 11. Note that 3.3V input is Vdd and is not allowed to go below 3.0V during normal operation. Setting the Ready/Lock/Start/Override register Lock bit has no effect on these registers. Input
2.5V VCCP 3.3V 5V 12V
Nominal Voltage
2.5V 2.25V 3.3V 5.0V 12.0V
Register Reading at Nominal Voltage
C0h C0h C0h C0h C0h
Maximum Voltage
3.32V 3.00V 4.38V 6.64V 16.00V
Register Reading at Maximum Voltage
FFh FFh FFh FFh FFh
Minimum Voltage
0V 0V 3.0V 0V 0V
Register Reading at Minimum Voltage
00h 00h AEh 00h 00h
Table 11 Voltage Limits vs Register Setting (MS Byte)
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ASC7621
Temperature Measurement Filtering
Filter Architecture
Each temperature reading is carefully filtered to remove spike transients and noise generated by the computer environment's effect on sensitive analog measurements. Filtering is tunable by the user and is applied in two general areas: 1. Immediately after the measurement process before assigning a measurement to a Temperature Zone. 2. After Temperature Zone assignment but before a fan is assigned to that Temperature Zone. An overview of this signal flow is in Figure 6 below.
Two Remote Diodes and Internal Diode Temperature Zone 1-4 Reports
- Converter
Spike & Smoothing Filter (User Tuned)
Tuning: Register 0Eh bits 6:4, Table 9 Filtered PECI Reports
Preliminary Specification - Subject to change without notice
Up to 4 PECI Addresses
Up to 7 Temperature Inputs into 4 Temperature Zone Assignments and Limit Evaluations
Fan Speed Control
Spike & Smoothing Filter (User Tuned)
4 Zone to 3 Fan PWM Assignments
Preliminary Specification - Subject to change without notice
PECI Input
Select Maximum From Each PECI Address
Spike & Smoothing Filter (User Tuned)
Tuning: Register 36h bits 2:0, Table 8
Tuning: Register 62h bits 3:0, Register 63h bits 7:4 and 3:0, Register 3Ch bits 3:0, Table 23
Figure 6 Measurement Filter Block Diagram Spike & Smoothing Filter Algorithm
The Spike & Smoothing Filter algorithm has two phases of filtering. First, a "No-Spike" value is created from the current and three previous values. The result is an average of the two remaining values when the high and low values are removed. The second phase is a user specified filter and coefficient. This filter determines a smoothed temperature value, Smooth Ti, N by taking the No-Spike Ti, subtracting the previous smoothed temperature, Smooth Ti-1, divided by 2 and adding that to the previously smoothed temperature. N and GAIN are coefficients selected internally to provide the spike filter smoothing time constants (step input response time) shown in Table 8, Table 9 and Table 23. For the current temperature reading Ti: No-Spike Ti = (Discard min and max of (Ti, Ti-1, Ti-2, Ti-3))/2 Smooth Ti = GAIN * (No-Spike Ti - Smooth Ti-1)/2N + Smooth Ti-1
Status Registers
Register 41h: Interrupt Status Register 1
Register Address
41h
Read/ Write
R
Register Name
Interrupt Status 1
Bit 7 (MSB)
ERR
Bit 6
ZN3
Bit 5
ZN2
Bit 4
ZN1
Bit 3
5V
Bit 2
3.3V
Bit 1
VCCP
Bit 0 (LSB)
2.5V
Default Value
N/A
The Interrupt Status Register 1 bits will be automatically set, by the ASC7621, whenever a fault condition is detected. A fault condition is detected whenever a measured value is outside the window set by its limit registers. ZN1 bit will be set when a diode fault condition, such as an open or short, is detected. More than one fault may be indicated in the interrupt register when read. The register will hold set bit(s) until the event is read by software. The contents of this register will be cleared (set to 0) automatically by the ASC7621 after it is read by software, if the fault condition no longer exists. Once set, the Interrupt Status Register 1 bits will remain set until a read event occurs, even if the fault condition no longer exists. This register is read-only - a write to this register has no effect.
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ASC7621
Bit
0
Name
2.5V Limits Exceeded Vccp Limits Exceeded 3.3V Limits Exceeded 5V Limits Exceeded
R/W
R
Default
0
Description
The ASC7621 automatically sets this bit to 1 when the 2.5V input voltage is less than or equal to the limit set in the 2.5V Low Limit register or greater than the limit set in the 2.5V High Limit register. The ASC7621 automatically sets this bit to 1 when the VCCP input voltage is less than or equal to the limit set in the VCCP Low Limit register or greater than the limit set in the VCCP High Limit register. The ASC7621 automatically sets this bit to 1 when the 3.3V input voltage is less than or equal to the limit set in the 3.3V Low Limit register or greater than the limit set in the 3.3V High Limit register. The ASC7621 automatically sets this bit to 1 when the 5V input voltage is less than or equal to the limit set in the 5V Low Limit register or greater than the limit set in the 5V High Limit register. The ASC7621 automatically sets this bit to 1 when the temperature input measured by the Remote1- and Remote1+ inputs is less than or equal to the limit set in the Processor (Zone 1) Low Temp register or more than the limit set in the Processor (Zone 1) High Temp register. This bit will be set when a diode fault is detected. The ASC7621 automatically sets this bit to 1 when the temperature input measured by the internal temperature sensor is less than or equal to the limit set in the thermal (Zone 2) Low Temp register or greater than the limit set in the Internal (Zone 2) High Temp register. The ASC7621 automatically sets this bit to 1 when the temperature input measured by the second remote temperature sensor is less than or equal to the limit set in the thermal (Zone 3) Low Temp register or greater than the limit set in the Internal (Zone 3) High Temp register. If there is a set bit in Status Register 2, this bit will be set to 1.
1
R
0
2
R
0
3
R
0
4
Zone 1 Limit Exceeded
R
0
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
5
Zone 2 Limit Exceeded
R
0
6
Zone 3 Limit Exceeded Error in Status Register 2
R
0
7
R
0
Table 12 Interrupt Status Register 1 Register 42h: Interrupt Status Register 2
Register Address
42h
Read/ Write
R
Register Name
Bit 7 (MSB)
ERR2
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
12V
Default Value
N/A
Interrupt Status 2
ERR1
FAN4
FAN3
FAN2
FAN1
ERR
The Interrupt Status Register 2 bits will be automatically set, by the ASC7621, whenever a fault condition is detected. Interrupt Status Register 2 identifies faults caused by temperature sensor error, fan speed dropping below minimum set by the tachometer minimum register. Interrupt Status Register 2 will hold a set bit until the event is read by software. The contents of this register will be cleared (set to 0) automatically by the ASC7621 after it is read by software, if fault condition no longer exists. Once set, the Interrupt Status Register 2 bits will remain set until a read event occurs, even if the fault no longer exists. This register is read-only - a write to this register has no effect. Bit
0
Name
12V Limits Exceeded ERROR IN STATUS REGISTER 3 FAN 1 STALLED FAN 2 STALLED FAN 3 STALLED FAN 4 STALLED
R/W
R
Default
0
Description
The ASC7621 automatically sets this bit to 1 when the 12V input voltage is less than or equal to the limit set in the 12V Low Limit register or greater than the limit set in the 12V High Limit register. If there is a set bit in Status Register 3, this bit will be set to 1 The ASC7621 automatically sets this bit to 1 when the TACH 1 input reading is above the count value set in the Tach 1 Minimum MSB and LSB registers. The ASC7621 automatically sets this bit to 1 when the TACH 2 input reading is above the count value set in the Tach 2 Minimum MSB and LSB registers. The ASC7621 automatically sets this bit to 1 when the TACH 3 input reading is above the count value set in the Tach 3 Minimum MSB and LSB registers. The ASC7621 automatically sets this bit to 1 when the TACH 4 input reading is above the count value set in the Tach 4 Minimum MSB and LSB registers. - 25 www.andigilog.com
1 2 3 4 5
R R R R R
0 0 0 0 0
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ASC7621
Bit
6
Name
Remote Diode 1 Fault Remote Diode 2 Fault
R/W
R
Default
0
Description
The ASC7621 automatically sets this bit to 1 when there is an open circuit fault on the Remote1+ or Remote1- thermal diode input pins. A diode fault will also set bit 4 Zone 1 Limit bit, of Interrupt Status Register 1. The ASC7621 automatically sets this bit to 1 when there is an open circuit fault on the Remote2+ or Remote2- thermal diode input pins. A diode fault will also set bit 6 Zone 3 Limit bit, of Interrupt Status Register 1.
7
R
0
Table 13 Interrupt Status Register 2 Register 43h: Interrupt Status Register 3
Register Address
43h
Read/ Write
R
Register Name
Interrupt Status 3
Bit 7 (MSB)
RES
Bit 6
RES
Bit 5
RES
Bit 4
RES
Bit 3
ALOVR
Bit 2
COMM
Bit 1
DATA
Bit 0 (LSB)
ZN4
Default Value
N/A
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
The Interrupt Status Register 3 bits will be automatically set, by the ASC7621, whenever a fault condition is detected. Interrupt Status Register 3 identifies faults caused by Temperature Zone exceeding absolute limits, PECI Communication Error, PECI Data Error and Zone 4 Temperature limit exceeded. Interrupt Status Register 3 will hold a set bit until the event is read by software. The contents of this register will be cleared (set to 0) automatically by the ASC7621 after it is read by software, if fault condition no longer exists. Once set, the Interrupt Status Register 3 bits will remain set until a read event occurs, even if the fault no longer exists. This register is read only - a write to this register has no effect. Bit
0 1
Name
ZN4 DATA
R/W
R R
Default
0 0
Description
The ASC7621 automatically sets this bit to 1 when the Zone 4 Limit is exceeded. The ASC7621 sets this bit when any of the PECI Processor Status reports PECI ERROR = 1 and PECI Underflow = 1, this indicates a Data error occurred with a PECI processor. The ASC7621 automatically sets this bit to 1 when any of the PECI Processor Status reports PECI ERROR = 1 and PECI Underflow = 0 this indicates a Communications error occurred with a PECI Processor. The ASC7621 automatically sets this bit to 1 when any Temperature Zone exceeds its Absolute Temperature Limit. Reserved. Reserved. Reserved. Reserved.
2 3 4 5 6 7
COMM ALOVR Reserved Reserved Reserved Reserved
R R R R R R
0 0 0 0 0 0
Table 14 Interrupt Status Register 3
Tachometer Measurement and Configuration
Register 28-2Fh: Fan Tachometer Reading
Register Address
28h 29h 2Ah 2Bh 2Ch 2Dh 2Eh 2Fh
Read/ Write
R R R R R R R R
Register Name
Tach 1 LS Byte Tach 1 MS Byte Tach 2 LS Byte Tach 2 MS Byte Tach 3 LS Byte Tach 3 MS Byte Tach 4 LS Byte Tach 4 MS Byte
Bit 7 (MSB)
7 15 7 15 7 15 7 15
Bit 6
6 14 6 14 6 14 6 14
Bit 5
5 13 5 13 5 13 5 13
Bit 4
4 12 4 12 4 12 4 12
Bit 3
3 11 3 11 3 11 3 11
Bit 2
2 10 2 10 2 10 2 10
Bit 1
1 9 1 9 1 9 1 9
Bit 0 (LSB)
0 8 0 8 0 8 0 8
Default Value
N/A N/A N/A N/A N/A N/A N/A N/A
The Fan Tachometer Reading registers contains the number of 11.111s periods (90 kHz) between full fan revolutions. The results are based on the time interval of two tachometer pulses, since most fans produce two tachometer pulses per full
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ASC7621
revolution. These registers will be updated at least once every second. Common interpretation of tachometer readings is to take the binary period measurement and convert it to RPM. This may be done by applying the formula: RPM = (90,000 x 60)/(Decimal Equivalent of binary Tach Reading) The value, for each fan, is represented by a 16-bit unsigned number. The Fan Tachometer Reading registers will always return an accurate fan tachometer measurement, even when a fan is disabled or non-functional, however, if PWM commands for a fan (register 30h to 32h) is zero, tach measurements are suspended and the last reading may remain in the register. In the case of a three-wire fan being driven by PWM signal connected to fan power, the PWM output is held high for the period of the tachometer measurement. This stretching of the PWM will result in an exaggeration of the PWM command at low RPM. These registers are read-only - a write to these registers has no effect. When the LS Byte of the ASC7621 16-bit register is read, the other byte (MS Byte) is latched at the current value until it is read. At the end of the MS Byte read the Fan Tachometer Reading registers are updated. During spin-up, the PWM duty cycle reported is 0%.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Registers 54-5Bh: Fan Tachometer Limits
Register Address
54h 55h 56h 57h 58h 59h 5Ah 5Bh
Read/ Write
R/W R/W R/W R/W R/W R/W R/W R/W
Register Name
Tach 1 Minimum LS Byte Tach 1 Minimum MS Byte Tach 2 Minimum LS Byte Tach 2 Minimum MS Byte Tach 3 Minimum LS Byte Tach 3 Minimum MS Byte Tach 4 Minimum LS Byte Tach 4 Minimum MS Byte
Bit 7 (MSB)
7 15 7 15 7 15 7 15
Bit 6
6 14 6 14 6 14 6 14
Bit 5
5 13 5 13 5 13 5 13
Bit 4
4 12 4 12 4 12 4 12
Bit 3
3 11 3 11 3 11 3 11
Bit 2
2 10 2 10 2 10 2 10
Bit 1
1 9 1 9 1 9 1 9
Bit 0 (LSB)
0 8 0 8 0 8 0 8
Default Value
FF FF FF FF FF FF FF FF
The Fan Tachometer Low Limit registers indicate the tachometer reading under which the corresponding bit will be set in the Interrupt Status Register 2 register. In Auto Fan Control mode, the fan can run at low speeds, so care should be taken in software to ensure that the limit is high enough not to cause sporadic alerts. The fan tachometer will not cause a bit to be set in Interrupt Status Register 2 if the current value in Current PWM Duty registers (30h to 32h) is 00h or if the fan is disabled via the Fan Configuration Register. Interrupts will not be generated for a fan if its minimum is set to FF FFh except for timeout. Setting the Ready/Lock/Start/Override register Lock bit has no effect on these registers. Given the relative insignificance of Bit 0 and Bit 1, these bits could be programmed to designate the physical location of the fan generating the tachometer signal, as follows:
Register Name
CPU Cooler Memory Controller Chassis Front Chassis Rear
Bit 1
0 0 1 1
Bit 0 (LSB)
0 1 0 1
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ASC7621
Register 04-07h: Fan Tachometer Measurement Configuration
Register Address
04h
Read/ Write
R/W
Register Name
Tach 1 Configuration Tach 2 Configuration Tach 3 Configuration Tach 4 Configuration
Bit 7 (MSB)
3-Wire Enable 1 3-Wire Enable 1 3-Wire Enable 1 3-Wire Enable 1
Bit 6
3-Wire Enable 0 3-Wire Enable 0 3-Wire Enable 0 3-Wire Enable 0
Bit 5
Meas Blank 1 Meas Blank 1 Meas Blank 1 Meas Blank 1
Bit 4
Meas Blank 0 Meas Blank 0 Meas Blank 0 Meas Blank 0
Bit 3
Meas Dwell 1 Meas Dwell 1 Meas Dwell 1 Meas Dwell 1
Bit 2
Meas Dwell 0 Meas Dwell 0 Meas Dwell 0 Meas Dwell 0
Bit 1
Meas Duration 1 Meas Duration 1 Meas Duration 1 Meas Duration 1
Bit 0 (LSB)
Meas Duration 0 Meas Duration 0 Meas Duration 0 Meas Duration 0
Default Value
36
Lock
X
05h
R/W
36
X
06h
R/W
36
X
07h
R/W
36
X
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
The Fan Tachometer Configuration registers contain the settings that define the modes of measurement of the Tachometer input signals. The user is allowed to disable a tachometer measurement or to request PWM stretching, in the case of a 3wire fan. Also, the rate, start-up and period of measurements within a fan rotation cycle may be selected. The table below describes the controls. This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. Bit Name R/W Default Description
The amount of fan rotation used for the tach measurement. Assumes 2 pulse periods per rotation of fan. 1:0 Measurement Duration R/W 10 00: 1/4 Rotation - Tach Count x4 = Reported Value 01: 1/2 Rotation - Tach Count x2 = Reported Value 10: 1 Rotation - Tach Count x1 = Reported Value (default) 11: 2 Rotation - Tach Count x1 = Reported Value Delay between Tach Measurements 3:2 Measurement Dwell R/W 01 00: 100 ms 01: 300 ms (default) 10: 500 ms 11: 728 ms In 3-wire fan mode, a delay is needed to assure that the tach input has stabilized after the PWM has been set to 100% 5:4 Measurement Blank R/W 11 00: 11.1 s 01: 22.2 s 10: 33.3 s 11: 44.4 s (default) For 3-Wire mode, the PWM output will be forced to 100% when the tach measurement is being processed. Each fan has a 3Wire Mode control that will behave as indicated in this table: HLFRQ (5Fh-61h) 0 7:6 3-Wire Enable R/W 00 0 0 0 1 1 1 1 3-Wire Mode Enabled Enabled Enabled Disabled Disabled Disabled Enabled Disabled
3-Wire Enable (7:6) 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1
Table 15 Tachometer Configuration Register
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ASC7621
Automatic Fan Control
Auto Fan Control Operating Mode
The ASC7621 includes the circuitry for automatic fan control. In Auto Fan Mode, the ASC7621 will automatically adjust the PWM duty cycle of the PWM output. PWM outputs are assigned to a thermal zone based on the fan configuration registers. At any time, the temperature of a zone exceeds its Absolute Limit, all PWM outputs will go to 100% duty cycle to provide maximum cooling to the system.
Fan Temp Limit less Hysteresis Fan Temp Limit Fan Temp Limit plus Range Absolute Limit
Preliminary Specification - Subject to change without notice
Hysteresis (0 C to 15 C)
Range (2 C to 80 C)
rly inea cl e l arly y Cy Temp ut line M D g with cle Temp Cy PW asin uty g with e MD Incr PW creasin De
Preliminary Specification - Subject to change without notice
100%
PWM Set to Minimum
PWM %
User Choice: Set to Minimum or Off PWM Set to Off
0% Temperature
PWM set to Off or Minimum Below this Temperature
Linear Control Range
PWM 100%
Example
Temperature C
5 C Hysteresis 45 50
8 C Range 58 80
100% Off/ Min% Min% Minimum PWM set to 50%, fan speed increases linearly beyond 50 C but will not return to off until it has gone below Fan Temp Limit by the 5 C Hysteresis setting to 45C.
PWM %
Figure 7 Automatic Fan Speed Control Example
Example for PWM1 assigned to Zone 1: * * * Zone 1 Fan Temp Limit (Register 67h) is set to 50C (32h). Zone 1 Range (Register 5Fh) is set to 8C (6xh). Fan PWM Minimum (Register 64h) is set to 50% (80h).
In this case, the PWM duty cycle will be 50% at 50C. Since (Zone 1 Fan Temp Limit) + (Zone 1 Range) = 50C + 8C = 58C, the fan will run at 100% duty cycle when the temperature of the Zone 1 sensor reaches 58C. Since the midpoint of the fan control range is 54C, and the median duty cycle is 75% (Halfway between the PWM Minimum and 100%), PWM1 duty cycle would be 75% at 54C. Above (Zone 1 Fan Temp Limit) + (Zone 1 Range), the duty cycle will be 100%.
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ASC7621
Automatic Fan Speed Control using Maximum PWM Setting
The previously described and illustrated mode had no restriction on the maximum PWM setting. It is useful to limit the maximum PWM command sent to the fan in order to minimize the acoustic impact. The Maximum PWM setting will clamp the automatic fan PWM command at a user selected value. The Absolute Limit setting will still cause the PWM command to be 100% and that will remain until the temperature falls below the Absolute Limit temperature by an amount equal to the hysteresis setting. This will minimize the acoustic impact of having a temperature moving back and forth close to the Absolute Limit. The Absolute Limit may be set above or below the Fan Temp Limit plus Range. The PWM value will be overridden and will follow the hysteresis curve in either case, but the acoustic impact will be different, running the fan to 100% PWM at a lower temperature, but enhancing the cooling effect. Absolute Limit set on the low end is shown in Figure 8Figure 7. Setting it above is shown in Figure 9. It is important to consider the combination of Fan Temp Limit, Range, Maximum PWM and Absolute Limit and their impact on cooling and acoustics. In addition, the capability to operate a fan from a combination of thermal zones allows a compound linear slope to be achieved for further optimization.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Fan Temp Limit less Hysteresis
Fan Temp Limit
Absolute Limit
Fan Temp Limit plus Range
Hysteresis (0 C to 15 C)
Range (2 C to 80 C)
Hysteresis (0 C to 15 C)
Maximum PWM %
Fan Speed
Fan Set to Minimum Fan Set to Off
arly line e ycl emp T arly ty C ine Du g with le l Temp M in yc th PW reas i ty C Du sing w Inc M ea PW ecr D
Temperature
PWM set to Off
Linear Control Range
PWM 100%
Figure 8 Fan Control with Absolute Limit Set below Fan Temp Limit Plus Range
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ASC7621
Fan Temp Limit less Hysteresis Fan Temp Limit Fan Temp Limit plus Range Absolute Limit
Hysteresis (0 C to 15 C)
Range (2 C to 80 C)
Hysteresis (0 C to 15 C)
Maximum PWM %
Fan Speed
Fan Set to Minimum Fan Set to Off
arly ine le l m p yc e rly T ty C nea Du g with e li Temp Mn ycl th PW reasi i ty C Du sing w Inc M a PW ecre D
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Temperature
PWM set to Off
Linear Control Range
PWM 100%
Figure 9 Fan Control with Absolute Limit Set above Fan Temp Limit Plus Range
Auto Fan Mode Initiated End Polling Cycle No Min Speed or Spin-Up Time Met? End Fan Spin Up Begin Polling Cycle
Yes
Yes
Fan Spinning Up? No
Override PWM Output to 100%
Yes
Temp >= AbsLimit? No Set Fan Output to Max PWM Set Fan Output to 0%
Set fan output to auto fan mode minimum speed
No
Below Hysteresis? Yes
Yes
PWM= 100%? No PWM= = Limit? Yes No Off / Min set to 1? No (off)
No No Below Hysteresis? Yes
Yes (Minimum Speed)
Set Fan Output to 100%
Begin Fan Spin up
Yes
Fan Output at 0%? No Set fan speed based on Auto Fan Range Algorithm
Fan Output At 0%? Yes
No
Figure 10 Automatic Fan Control Algorithm
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ASC7621
Fan Register Device Set-Up
The BIOS will follow the following steps to configure the fan registers on the ASC7621. The registers corresponding to each function are listed. All steps may not be necessary if default values are acceptable. Regardless of all changes made by the BIOS to the fan limit and parameter registers during configuration, the ASC7621 will continue to operate based on default values until the START bit (bit 0), in the Ready/Lock/Start/Override register (address 40h), is set. Once the fan mode is updated, by setting the START bit to 1, the ASC7621 will operate using the values that were set by the BIOS in the fan control limit and parameter registers (address in the range 3Ch through 75h). It is assumed that each Temperature Zone has already been configured to be associated with the appropriate temperature measurement either with the default settings or to the user's preference. See previous section on Temperature Zone configuration. 1. Set limits and parameters (not necessarily in this order): * * * [3Ch, 5F-61h] Set PWM frequency for the fan and auto fan control range for each zone. [3Ch, 62-63h] Set spike smoothing and min/off. [5C-5Eh] Set the fan spin-up delay. [75h] Set PWM spin-up mode to terminate after time set in [5C-5Eh]. Value = 00h instead of default 01h. [5C-5Eh] Match fan with a corresponding thermal zone. [3Bh, 67-69h] Set the fan temperature limits. [3Dh, 6A-6Ch] Set the temperature absolute limits. [64-66h] Set the PWM minimum duty cycle. [6D-6Eh] Set the temperature hysteresis values.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
* * * * * * 2.
[40h] Set bit 0 (START) to update fan control and limit register values and start fan control based on these new values.
[40h] (Optional) Set bit 1 (LOCK) to lock the fan limit and parameter registers. WARNING: this is a non-reversible change in state and locks out further change in critical fan control parameters until power is removed from the ASC7621.
Register 5F-61h: Auto Fan Speed Range, PWM Frequency
Register Address
5Fh 60h 61h 3Ch
Read/ Write
R/W R/W R/W R/W
Register Name
Zone 1 Range Fan1 Frequency Zone 2 Range/ Fan 2 Frequency Zone 3 Range/ Fan 3 Frequency Zone 4 Range, Spike Smoothing
Bit 7 (MSB)
RAN3 RAN3 RAN3 RAN3
Bit 6
RAN2 RAN2 RAN2 RAN2
Bit 5
RAN1 RAN1 RAN1 RAN1
Bit 4
RAN0 RAN0 RAN0 RAN0
Bit 3
HLFRQ HLFRQ HLFRQ ZN4E
Bit 2
FRQ2 FRQ2 FRQ2 ZN4-2
Bit 1
FRQ1 FRQ1 FRQ1 ZN4-1
Bit 0 (LSB)
FRQ0 FRQ0 FRQ0 ZN4-0
Default Value
C3 C3 C3 C3h
Lock
X X X X
In Auto Fan Mode, when the temperature for a zone is above the Temperature Limit (Registers 3Bh, 67-69h) and below its Absolute Temperature Limit (Registers 3Dh 6A-6Ch), the speed of a fan assigned to that zone is determined as follows: When the temperature reaches the Fan Temp Limit for a zone, the PWM output assigned to that zone will be Fan PWM Minimum. Between Fan Temp Limit and (Fan Temp Limit + Range), the PWM duty cycle will increase linearly according to the temperature as shown in the figure below. The PWM duty cycle will be 100% at (Fan Temp Limit + Range). PWM frequency - FRQ[3:0] and HLFRQ The PWM frequency bits [3:0] determine the PWM frequency for the fan. The ASC7621 has high and low frequency ranges for the PWM outputs that are controlled by the HLFRQ bit. PWM Frequency Selection (Default = 0011 30 Hz).
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ASC7621
HLFRQ
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
FRQ [2:0]
000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111
PWM Frequency
~10 Hz ~15 Hz ~23 Hz ~30 Hz (Default) ~38 Hz ~47 Hz ~62 Hz ~94 Hz ~23 kHz ~24 kHz ~25 kHz ~26 kHz ~27 kHz ~28 kHz ~29 kHz ~30 kHz
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Table 16 Register Setting vs PWM Frequency
RAN[3:0]
0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
Linear Control Range (C)
2 2.5 3.33 4 5 6.67 8 10 13.33 16 20 26.67 32 (default) 40 53.33 80
Table 17 Zone Range Setting, RAN[3:0]
This register becomes Read-Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. After power up the default value is used for bits 3:0 of registers 5F-61h whenever the Ready/Lock/Start/Override register Start bit is cleared even though modifications to this register are possible.
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ASC7621
Register 40h: Ready/Lock/Start/Override
Register Address
40h
Read/ Write
R/W
Register Name
Ready/Lock/Start/ Override
Bit 7 (MSB)
RES
Bit 6
RES
Bit 5
SAFE
Bit 4
PECI
Bit 3
OVRID
Bit 2
READY
Bit 1
LOCK
Bit 0 (LSB)
START
Default Value
00
Bit
Name
R/W
Default
Description
When software writes a 1 to this bit, the ASC7621 fan monitoring and PWM output control functions will use the values set in the fan control limit and parameter registers (addresses 30-32h and 5Fh through 61h). Before this bit is set, the ASC7621 will not update the used register values, the default values will remain in effect. Whenever this bit is set to 0, the ASC7621 fan monitoring and PWM output control functions use the default fan limits and parameters, regardless of the current values in the limit and parameter registers (addresses 30-32h and 5Fh through 61h). The ASC7621 will preserve the values currently stored in the limit and parameter registers when this bit set or cleared. This bit is not affected by the state of the Lock bit. It is expected that all limit and parameter registers will be set by BIOS or application software prior to setting this bit.
0
START
R/W
0
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
1
LOCK
R/W
0
Setting this bit to 1 locks specified limit and parameter registers. WARNING: Once this bit is set, limit and parameter registers become read-only and will remain locked until the device is powered off. This register bit becomes read-only once it is set. The ASC7621 sets this bit automatically after the part is fully powered up, has completed the power-up-reset process, and after all A/D converters are properly functioning. If this bit is set to 1, all PWM outputs will go to 100% duty cycle regardless of whether or not the lock bit is set. The OVRID bit has precedence over the disabled mode. Therefore, when OVRID is set the PWM will go to 100% even if the PWM is in the disabled mode. When software writes a 1 to this bit, support for the monitoring of Processor temperatures via the PECI interface is enabled. This bit becomes read only when the LOCK bit is set to 1. When software writes a 1 to this bit, it indicates that when operating the fan in manual mode, the PWM duty cycle will be overridden to 100% when any Zone exceeds its Absolute Limit. When the bit is set to 0, it indicates that when operating the fan in manual mode, the PWM duty cycle will not be overridden to 100% when any Zone exceeds its Absolute Limit. Reserved
2
READY
R
0
3
OVRID
R/W
0
4
PECI
R/W
0
5
SAFE
R/W
0
6-7
RESERVED
R
0
Table 18 READY / LOCK / START / OVRID Settings Register 30-32h: Current PWM Duty Cycle
Register Address
30h 31h 32h
Read/ Write
R/W R/W R/W
Register Name
Fan 1 Current PWM Duty Fan 2 Current PWM Duty Fan 3 Current PWM Duty
Bit 7 (MSB)
7 7 7
Bit 6
6 6 6
Bit 5
5 5 5
Bit 4
4 4 4
Bit 3
3 3 3
Bit 2
2 2 2
Bit 1
1 1 1
Bit 0 (LSB)
0 0 0
Default Value
FF FF FF
The Current PWM Duty registers store the current duty cycle at each PWM output. At initial power-on, the PWM duty cycle is 100% and thus, when read, this register will return FFh. After the Ready/Lock/Start/Override register Start bit is set, this register and the PWM signals will be updated based on the algorithm described in the Auto Fan Control Operating Mode section. When Ready/Lock/Start/Override register Start bit is zero, default value (FFh) is used.
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ASC7621
When read, the Current PWM Duty registers return the current PWM duty cycle. These registers are read-only unless the fan is in manual (test) mode, in which case a write to these registers will directly control the PWM duty cycle for each fan. The PWM duty cycle is represented as shown in Table 19. If a 3-wire fan is being used and the option to enable 3-wire tach measurement is selected, the effective PWM duty cycle will be impacted by this feature. The 3-wire Enable setting will hold the PWM signal high for the period taken to make a tachometer reading. This period depends on the RPM and various tachometer measurement parameters. Overall impact is that lower PWM commands will be effectively increased and there may be acoustic effects.
Current PWM % 0% ~25%
Register Value Binary 0000 0100 1000 1100 1111 0000 0000 0000 0000 1111 Hex 00 40 80 C0 FF
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
~50% (Default) ~75% 100%
Table 19 Current PWM Duty Cycle Setting Register 4E-53h and 39h-3Ah: Temperature Zone Limit Registers
Register Address
4Eh 4Fh 50h 51h 52h 53h 34h 3Ah
Read/ Write
R/W R/W R/W R/W R/W R/W R/W R/W
Register Name
Zone 1 Low Temperature Zone 1 High Temperature Zone 2 Low Temperature Zone 2 High Temperature Zone 3 Low Temperature Zone 3 High Temperature Zone 4 Low Temperature Zone 4 High Temperature
Bit 7 (MSB)
7 7 7 7 7 7 7 7
Bit 6
6 6 6 6 6 6 6 6
Bit 5
5 5 5 5 5 5 5 5
Bit 4
4 4 4 4 4 4 4 4
Bit 3
3 3 3 3 3 3 3 3
Bit 2
2 2 2 2 2 2 2 2
Bit 1
1 1 1 1 1 1 1 1
Bit 0 (LSB)
0 0 0 0 0 0 0 0
Default Value
81 7F 81 7F 81 7F 81 00
If an external temperature input or the internal temperature sensor either exceeds the value set in the corresponding high limit register or falls below the value set in the corresponding low limit register, the corresponding bit will be set automatically by the ASC7621 in the Interrupt Status Register 1 (41h). For example, if the temperature read from the Remote - and Remote + inputs exceeds the Zone 1 High Temp register limit setting, Interrupt Status Register 1 ZN1 bit will be set. The temperature limits in these registers are represented as 8 bit 2's complement, signed numbers in Celsius, as shown below in Table 20. Setting the Ready/Lock/Start/Override register Lock bit has no effect on these registers.
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ASC7621
Temperature >127C +127C (Default High) +125C +90C +50C +25C 0C -50C -127C (Default Low) Temperature Limit (2's Complement) 0111 0111 0111 0101 0011 0001 0000 1100 1000 1111 1111 1101 1010 0010 1001 0000 1110 0001
Table 20 Temperature Zone High- and Low-Limit Registers - 8-Bit Two's Complement
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Register 5C-5Eh: Fan Temperature Zone Assignment and Spin-up Mode
Register Address
5Ch 5Dh 5Eh
Read/ Write
R/W R/W R/W
Register Name
Fan 1 Configuration Fan 2 Configuration Fan 3 Configuration
Bit 7 (MSB)
ZON2 ZON2 ZON2
Bit 6
ZON1 ZON1 ZON1
Bit 5
ZON0 ZON0 ZON0
Bit 4
INV INV INV
Bit 3
ALT ALT ALT
Bit 2
SPIN2 SPIN2 SPIN2
Bit 1
SPIN1 SPIN1 SPIN1
Bit 0 (LSB)
SPIN0 SPIN0 SPIN0
Default Value
62 62 62
Lock
X X X
This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. Bits [7:5] Zone/Mode and Bit [3] Alternate Zone/Mode Bits [7:5] of the Fan Configuration registers associate each fan with a Temperature Zone. When in Auto Fan Mode the fan will be assigned to a zone, and its PWM duty cycle will be adjusted according to the temperature of that zone. If "Hottest" option is selected (110), the fan will be controlled by the the hottest of zones 1, 2 or 3. To determine the "hottest zone", the PWM level for each zone is calculated then the zone with the higher PWM value (not temperature) is selected. When in manual control mode, the Current PWM duty register (30-32h) become Read/Write. It is then possible to control the PWM outputs with software by writing to these registers. When the fan is disabled (100) the corresponding PWM output should be driven low (or high, if inverted). Bit-3 enables an alternate set of definitions for the ZON[2:0] Zone/Mode bits described in Table 21. Fan Configuration ALT = 0
Fan on zone 1. Fan on zone 2. Fan on zone 3. Fan on full. PWM = 255. Fan disabled. PWM = 0. Fan controlled by hottest of 2, or 3. Fan controlled by hottest of zones 1, 2, and 3. Fan Manually controlled (Test Mode)
ZON [2:0]
000 001 010 011 100 101 110 111
Fan Configuration ALT = 1
Fan on zone 4. Fan controlled by hottest of zones 1, 2, 3, and 4. Reserved. (Fan on full. PWM = 255.) Reserved. (Fan on full. PWM = 255.) Vendor specific. (Fan on full. PWM = 255.) Vendor specific. (Fan on full. PWM = 255.) Vendor specific. (Fan on full. PWM = 255.) Vendor specific. (Fan on full. PWM = 255.)
ZON[2:0]
000 001 010 011 100 101 110 111
Table 21 Fan Zone Setting
Bit [4] PWM Invert Bit [4] inverts the PWM output. If set to 0, 100% duty cycle will yield an output that is always high. If set to 1, 100% duty cycle will yield an output that is always low. Bit [2:0] Spin Up Bits [2:0] specify the `spin up' time for the fan. When a fan is being started from a stationary state, the PWM output is held at 100% duty cycle for the time specified in the table below before scaling to a lower speed.
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ASC7621
Spin Up Time
0 ms 100 ms 250 ms 400 ms 700 ms 1000 ms 2000 ms 4000 ms
SPIN[2:0]
000 001 010 011 100 101 110 111
Table 22 Fan Spin-Up Register Register 00h: Zone Status
Preliminary Specification - Subject to change without notice
Register Address
00h
Read/ Write
R
Register Name
Fan Zone Status
Bit 7 (MSB)
1
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
RES
Default Value
N/A
Lock
Preliminary Specification - Subject to change without notice
Fan 3 Zone # 0
Fan 2 Zone # 1 0
Fan 1 Zone # 1 0
RES
The Fan Zone Status register reports the current Temperature Zone assignment to a fan. It reveals the actual assignment when the user has selected a mode in which the hottest of multiple zones to determine fan speed. Zone 1 = 01b, Zone 2 = 10b, Zone 3 = 11b and Zone 4 = 00b. If a fixed assignment or manual fan speed control is used these Zone #s will return 00b. This is a read-only register, a write has no effect.
Register 62h, 63h, 3Ch: Min/Off, Spike Smoothing
Register Address
62h 63h 3Ch
Read/ Write
R/W R/W R/W
Register Name
Min/Off, Zone1 Spike Smoothing Zone2 Spike Smoothing Zone 4 Range, Spike Smoothing
Bit 7 (MSB)
OFF3 ZN2E RAN3
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
ZN1-0 ZN3-0 ZN4-0
Default Value
00 00 C3h
Lock
OFF2 ZN2-2 RAN2
OFF1 ZN2-1 RAN1
RES ZN2-0 RAN0
ZN1E ZN3E ZN4E
ZN1-2 ZN3-2 ZN4-2
ZN1-1 ZN3-1 ZN4-1
X X X
The OFF1-OFF3 (Bits 7 to 5) specify whether the duty cycle will be 0% or Minimum Fan Duty when the measured temperature falls below the Temperature LIMIT register setting (see Table 24 below). If the Remote pins are connected to a processor or chipset, instantaneous temperature spikes may be sampled by the ASC7621. Temperature readings are first passed through a user-programmable filter described above in the Temperature Measurement Filter section and then assigned to a Temperature Zone for fan speed control. If these spikes are not filtered, the CPU fan (if connected to ASC7621) may turn on prematurely or produce unpleasant noise. For this reason, any zone that is connected to a chipset or processor should have spike smoothing enabled. Individual system characteristics will determine how large this coefficient should be. When spike smoothing is enabled, the temperature reading registers will contain a value that is the result of the first filter. A second filter acts on the assigned Temperature Zone and is "smoothed out" for fan speed control. Table 23 shows the approximate filter response time to a step function in Temperature Zone reading. ZN1E, ZN2E, ZN3E and ZN4E enable temperature smoothing for zones 1, 2, 3 and 4 respectively. ZN1-2, ZN1-1 and ZN1-0 control smoothing time for Zone 1. ZN2-2, ZN2-1 and ZN2-0 control smoothing time for Zone 2. ZN3-2, ZN3-1 and ZN3-0 control smoothing time for Zone 3. ZN4-2, ZN4-1 and ZN4-0 control smoothing time for Zone 4. These registers become read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to these registers shall have no effect.
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ASC7621
60 50 40 30 20 10 0 1 2 3 4 5 6 7 8 9 10 11 12
Figure 11 Representation of What Temperature Is Passed to the ASC7621 Auto Fan Control with (green) and without (red dashed) Spike Smoothing
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Spike Smoothing Time
35 seconds 17.6 seconds 11.8 seconds 7.0 seconds 4.4 seconds 3.0 seconds 1.6 seconds 0.8 seconds
ZNn-[2:0]
000 001 010 011 100 101 110 111
Table 23 Spike Smoothing for ZN1 to ZN4
PWM Action
At 0% duty below LIMIT At Min PWM Duty below LIMIT
Off/Min Bit
0 1
Table 24 PWM Output Below Limit Depending on Value of Off/Min Register 64-66h: Minimum PWM Duty Cycle
Register Address
64h 65h 66h
Read/ Write
R/W R/W R/W
Register Name
Fan 1 PWM Minimum Fan 2 PWM Minimum Fan 3 PWM Minimum
Bit 7 (MSB)
7 7 7
Bit 6
6 6 6
Bit 5
5 5 5
Bit 4
4 4 4
Bit 3
3 3 3
Bit 2
2 2 2
Bit 1
1 1 1
Bit 0 (LSB)
0 0 0
Default Value
80 80 80
Lock
X X X
This register specifies the minimum duty cycle that the PWM will output when the measured temperature reaches the Temperature LIMIT register setting. This register becomes Read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
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ASC7621
Minimum PWM % 0% ~25% ~50% (Default) ~75% 100% Register Value Binary 0000 0100 1000 1100 1111 0000 0000 0000 0000 1111 Hex 00 40 80 C0 FF
Table 25 Minimum PWM Duty Cycle Setting Register 38-3Ah: Maximum PWM Duty Cycle
Register Address Read/ Write
R/W R/W R/W
Register Name
Fan 1 Max Duty Cycle Fan 2 Max Duty Cycle Fan 3 Max Duty Cycle
Bit 7 (MSB)
7 7 7
Bit 6
6 6 6
Bit 5
5 5 5
Bit 4
4 4 4
Bit 3
3 3 3
Bit 2
2 2 2
Bit 1
1 1 1
Bit 0 (LSB)
0 0 0
Default Value
FF FF FF
Lock
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
38h 39h 3Ah
X X X
The Maximum PWM Duty registers store the maximum duty cycle that may be commanded at each PWM output under automatic fan control. This value is overridden to 100% when the assigned zone's temperature has exceeded the Absolute Maximum Temperature setting. When temperature falls below Absolute Maximum, PWM command will resume the linear ramp only after it has fallen by the Thermal Zone Hysteresis value (Registers 6D-6Eh). Values follow the representation in Table 19. This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
Register 67-69h: Temperature Limit
Register Address
67h 68h 69h 3Bh
Read/ Write
R/W R/W R/W R/W
Register Name
Zone 1 Fan Temp Limit Zone 2 Fan Temp Limit Zone 3 Fan Temp Limit Zone 4 Fan Temp Limit
Bit 7 (MSB)
7 7 7 7
Bit 6
6 6 6 6
Bit 5
5 5 5 5
Bit 4
4 4 4 4
Bit 3
3 3 3 3
Bit 2
2 2 2 2
Bit 1
1 1 1 1
Bit 0 (LSB)
0 0 0 0
Default Value
5A 5A 5A E0
Lock
X X X X
These are the temperature limits for the individual zones. When the current temperature equals this limit, the fan will be turned on if it is not already. When the temperature exceeds this limit, the fan speed will be increased according to the algorithm set forth in the Auto Fan Range, PWM Frequency register description, Default = 90C = 5Ah This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. Temperature >127C +127C +125C +90C (default)
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Fan Temp Limit (2's Complement) 0111 0111 0111 0101 1111 1111 1101 1010
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ASC7621
Temperature +50C +25C 0C -50C -127C Fan Temp Limit (2's Complement) 0011 0001 0000 1100 1000 0010 1001 0000 1110 0001
Table 26 Fan Temperature Limit Register 8-Bit Two's Complement Register 6A-6Ch: Temperature Limit
Preliminary Specification - Subject to change without notice
Register Address
6Ah 6Bh 6Ch 3Dh
Read/ Write
R/W R/W R/W R/W
Register Name
Zone 1 Temp Absolute Limit Zone 2 Temp Absolute Limit Zone 3 Temp Absolute Limit Zone 4 Temp Absolute Limit
Bit 7 (MSB)
7 7 7 7
Bit 6
6 6 6 6
Bit 5
5 5 5 5
Bit 4
4 4 4 4
Bit 3
3 3 3 3
Bit 2
2 2 2 2
Bit 1
1 1 1 1
Bit 0 (LSB)
0 0 0 0
Default Value
64 64 64 00
Lock
X X X X
Preliminary Specification - Subject to change without notice
In the Auto Fan mode, if a zone exceeds the temperature set in the Absolute Temperature Limit register, all of the PWM outputs will increase its duty cycle to 100%. This is a safety feature that attempts to cool the system if there is a potentially catastrophic thermal event. If set to 80h (-128C), the feature is disabled. Default = 100 C = 64h. The PWM will remain at 100% until the assigned Temperature Zone falls below the Absolute Temp Limit for that zone by an amount equal to the hysteresis value for that zone. These registers become read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to these registers shall have no effect.
Temperature >127C +127C +125C +100C (default) +50C +25C 0C -50C -127C -128C (Disable)
Absolute Limit (2's Complement) 0111 0111 0111 0110 0011 0001 0000 1100 1000 1000 1111 1111 1101 0100 0010 1001 0000 1110 0001 0000
Table 27 Absolute Temperature Limit Register 8-Bit Two's Complement
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ASC7621
Register 6D-6Eh: Thermal Zone Hysteresis
Register Address
6Dh
Read/ Write
R/W
Register Name
Zone 1 and Zone 2 Hysteresis Zone 3 and Zone 4 Hysteresis
Bit 7 (MSB)
H1-3
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0 (LSB)
H2-0
Default Value
44
Lock
H1-2
H1-1
H1-0
H2-3
H2-2
H2-1
X
6Eh
R/W
H3-3
H3-2
H3-1
H3-0
H4-3
H4-2
H4-1
H4-0
44
X
If the temperature is above Fan Temp Limit, then drops below Fan Temp Limit, the following will occur: * The fan will remain on, at Fan PWM Minimum, until the temperature goes a certain amount below Fan Temp Limit. * The Hysteresis registers control this amount. See below table for details, all values from 0C to 15C are possible. This register becomes read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to these registers shall have no effect.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Temperature 0C 1C 4C (default) 10C 15C
Zone Hysteresis Hn-[3:0] 0000 0001 0100 1010 1111
Table 28 Zone Hysteresis Register Format Register 75h: Fan Spin-Up Mode
Register Address
75h
Read/ Write
R/W
Register Name
Fan SpinUp Mode
Bit 7 (MSB)
Tach4 Disable
Bit 6
Tach3/4 Disable
Bit 5
Tach2 Disable
Bit 4
Tach1 Disable
Bit 3
RES
Bit 2
PWM3 SU
Bit 1
PWM2 SU
Bit 0 (LSB)
PWM1 SU
Default Value
00
Lock
X
The PWM SU bit configures the PWM spin-up mode. If PWM SU is cleared the spin-up time will terminate after time programmed by the Fan Configuration register has elapsed. When set to 1, the spin-up time will terminate early if the TACH reading interpreted as RPM exceeds the Tach Minimum RPM value or after the time programmed by the Fan Configuration register has elapsed, which ever occurs first. Note that the magnitudes of the tach readings and the limits in the registers represent a time period that is inversely proportional to RPM. This register becomes Read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect.
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ASC7621
Miscellaneous Registers
Registers 19h and 1Ah: GPIO Configuration
Register Address
19h 1Ah
Read/ Write
R/W R/W
Register Name
GPIO 1 Configuration GPIO 2 Configuration
Bit 7 (MSB)
RES GPIO 2 bit
Bit 6
Bit 5
Bit 4
Bit 3
GPIO 1 bit GPIO 3 bit
Bit 2
Bit 1
Bit 0 (LSB)
0 0
Default Value
00 00
Lock
RES
Alert Assignment 1 1 0 0
GPIO 1 Function 2 2 1 GPIO 3 Function 1
X X
GPIO 2 Function 2
Preliminary Specification - Subject to change without notice
GPIO pins are multi-function and may be used as input, output, bi-directional or may serve as an alarm pin with ALERT or THERM behavior. This is an open-drain output and a read returns the state of the pin, a write drives the pin based on the GPIO bit. This register becomes Read-only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this register shall have no effect. GPIO Configuration 1 contains two controls. The 1st is the ALERT Assignment and the 2nd is GPIO 1 pin definitions. 1. The Alert assignment defines which one of the GPIO pins that will source the Alert. The Alert assignment supersedes any GPIO pin configuration. 2. The GPIO 1 Function defines the configuration of the GPIO 1 pin. The default is to configure the pin as an input. Any zone Fan Temp Limit status can be sent to the pin or the written value of bit 3 can be sent to GPIO 1 pin. The read value of bit 3 indicates the level of the GPIO 1 pin not the state of the GPIO Register bit.
Preliminary Specification - Subject to change without notice
Bit
Field
GPIO Configuration 1 [19h] Value Function 000 (Default) GPIO PIN Read only, Output drive always set high. 001 Zone 1 Therm Status, pin = 0, Zone 1 exceeds Fan Temp Limit 010 Zone 2 Therm Status, pin = 0, Zone 2 exceeds Fan Temp Limit 011 Zone 3 Therm Status, pin = 0, Zone 3 exceeds Fan Temp Limit 100 Zone 4 Therm Status, pin = 0, Zone 4 exceeds Fan Temp Limit 101 Any Zone Therm Status, pin = 0, Any Zone exceeds Fan Temp Limit 110 GPIO PIN Read only, Output drive always set high. 111 GPIO PIN IO Mode, Output drive set to GPIO Reg.Bit 3. Read of this bit always returns value of GPIO 1 IO Pin. Write to this function sends value to GPIO 1 Pin when Function is IO mode. Value Function 00 (Default) No ALERT Function ALERT disabled 01 ALERT function sent to GPIO 1, pin = 0, ALERT Active 10 ALERT function sent to GPIO 2, pin = 0, ALERT Active 11 ALERT function sent to GPIO 3, pin = 0, ALERT Active Reserved Table 29 GPIO Configuration 1 [19h]
2:0
GPIO 1 Function
3
GPIO 1 Bit
5:4
Alert Assignment RES
7:6
GPIO Configuration 2 contains two controls. The 1st is GPIO 2 pin definition and the 2nd is GPIO 3 pin definition. 1. The GPIO 2 Function defines the configuration of the GPIO 2 pin. The default is to configure the pin as an input. Any zone therm status can be sent to the pin or the written value of bit 7 can be sent to GPIO 2 pin. The read value of bit 7 indicates the level of the GPIO 2 pin not the state of bit 7 register. 2. The GPIO 3 Function defines the configuration of the GPIO 3 pin. The default is to configure the pin as an input. Any zone therm status can be sent to the pin or the written value of bit 3 can be sent to GPIO 3 pin. The read value of bit 3 indicates the level of the GPIO 3 pin not the state of bit 3 register
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ASC7621
Bit Field GPIO Configuration 2 [1Ah] Value Function 000 (Default) GPIO PIN Read only Output drive always set high. 001 Zone 1 Therm Status, pin = 0, Zone 1 exceeds Fan Temp Limit 010 Zone 2 Therm Status, pin = 0, Zone 2 exceeds Fan Temp Limit 011 Zone 3 Therm Status, pin = 0, Zone 3 exceeds Fan Temp Limit 100 Zone 4 Therm Status, pin = 0, Zone 4 exceeds Fan Temp Limit 101 Any Zone Therm Status, pin = 0, Any Zone exceeds Fan Temp Limit 110 GPIO PIN Read only, Output drive always set high. 111 GPIO PIN IO Mode, Output drive set to GPIO Reg.Bit 3. Read of this bit always returns value of GPIO 3 IO Pin. Write to this function sends value to GPIO 3 Pin when Function is IO mode. Value Function 000 (Default) GPIO PIN Read only Output drive always set high. 001 Zone 1 Therm Status, pin = 0, Zone 1 exceeds Fan Temp Limit 010 Zone 2 Therm Status, pin = 0, Zone 2 exceeds Fan Temp Limit 011 Zone 3 Therm Status, pin = 0, Zone 3 exceeds Fan Temp Limit 100 Zone 4 Therm Status, pin = 0, Zone 4 exceeds Fan Temp Limit 101 Any Zone Therm Status, pin = 0, Any Zone exceeds Fan Temp Limit 110 GPIO PIN Read only Output drive always set high. 111 GPIO PIN IO Mode Output drive set to GPIO Reg.Bit 7. Read of this bit always returns value of GPIO 2 IO Pin. Write to this function sends value to GPIO 2 Pin when Function is IO mode. Table 30 GPIO Configuration 2 [1Ah] Register 3Eh: Company ID
Register Address
3Eh
2-0
GPIO 3 Function
3
GPIO 3 Bit
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
7:4
Alert Assignment
7
GPIO 2 Bit
Read/ Write
R
Register Name
Company ID
Bit 7 (MSB)
7
Bit 6
6
Bit 5
5
Bit 4
4
Bit 3
3
Bit 2
2
Bit 1
1
Bit 0 (LSB)
0
Default Value
61
The company ID register contains the company identification number. For Andigilog this is 61h. This number is assigned by Intel and is a method for uniquely identifying the part manufacturer. This register is read-only - a write to this register has no effect.
Register 3Fh: Version/Stepping
Register Address
3Fh
Read/ Write
R
Register Name
Version/Stepping
Bit 7 (MSB)
VER3
Bit 6
VER2
Bit 5
VER1
Bit 4
VER0
Bit 3
4WIRE
Bit 2
PECI
Bit 1
STP1
Bit 0 (LSB)
STP0
Default Value
6C
The two least significant bits of the Version/Stepping register [1:0] contain the current stepping of the ASC7621 silicon. The four most significant bits [7:4] reflect the ASC7621 base device number when set to a value of 0110b. For the ASC7621, this register will read 01101100b (6Ch). The register is used by application software to identify which device in the hardware monitor family has been implemented in the given system. Based on this information, software can determine which registers to read from and write to. Further, application software may use the current stepping to implement work-around for bugs found in a specific silicon stepping. This register is read-only - a write to this register has no effect.
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ASC7621
Register 6Fh: Test Register
Register Address
6Fh
Read/ Write
R/W
Register Name
Test Register
Bit 7 (MSB)
RES
Bit 6
RES
Bit 5
RES
Bit 4
RES
Bit 3
RES
Bit 2
RES
Bit 1
RES
Bit 0 (LSB)
XEN
Default Value
00h
Lock
X
XOR Tree Test
The ASC7621 incorporates a XOR tree test mode. When the test mode is enabled by setting the "XEN" bit high in the Test Register at address 6Fh via the SMBus, the part will enter XOR test mode. Since the test mode an XOR tree, the order of the signals in the tree is not important. SMBDAT and SMBCLK are not included in the test tree. Connections to the XOR tree are shown in Figure 12. This register becomes Read-Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this registers shall have no effect.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
PWM2 PWM3 TACH1 TACH2 XTESTOUT TACH3 TACH4
Figure 12 XOR Test Tree Register 70-7Fh: Vendor Specific Registers
These registers are for vendor specific features, including test registers. They will not default to a specific value on power up.
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ASC7621
Applications Information
Remote Diodes
The ASC7621 is designed to work with a variety of remote sensors in the form of the substrate thermal diode of a CPU or graphics controller or a diode-connected transistor. Actual diodes are not suited for these measurements. There is some variation in the performance of these diodes, described in terms of its departure from the ideal diode equation. This factor is called diode nonideality, nf . The equation relating diode temperature to a change in thermal diode voltage with two driving currents is: Although the temperature error caused by non-ideality difference is directly proportional to the difference from 1.008, but a small difference in non-ideality results in a relatively large difference in temperature reading. For example, if there were a 1% tolerance in the non-Ideality of a diode it would result in a 2.7 degree difference (at 0C) in the result (0.01 x 273.15). This difference varies with temperature such that a fixed offset value may only be used over a very narrow range. Typical correction method required when measuring a wide range of temperature values is to scale the temperature reading in the host firmware.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
VBE
where:
KT = (nf ) ln( N ) q
Part PentiumTM III (CPUID 68h) Pentium 4, 130nM Pentium 4, 90nM Pentium 4, 65nM Intel Pentium M AMD AthlonTM Model 6 AMD DuronTM Models 7 and 8 AMD Athlon Models 8 and 10 2N3904
nf Min
1.0057 1.001
nf Nom
1.008 1.002 1.011 1.009
nf Max
1.0125 1.003
Series Res
nf = diode non-ideality factor, (nominal 1.009). -23 K = Boltzman's constant, (1.38 x 10 ). T = diode junction temperature in Kelvins. -19 q = electron charge (1.6 x 10 Coulombs). N = ratio of the two driving currents (16).
The ASC7621 is designed and trimmed for an expected nf value of 1.009, based on the typical value for the Intel PentiumTM III and AMD AthlonTM. There is also a tolerance on the value provided. The values for other CPUs and the 2N3904 may have different nominal values and tolerances. Consult the CPU or GPU manufacturer's data sheet for the nf factor. Table 31 gives a representative sample of what one may expect in the range of non-ideality. The trend with CPUs is for a lower value with a larger spread. When thermal diode has a non-ideality factor other than 1.009 the difference in temperature reading at a particular temperature may be interpreted with the following equation:
1.009 Tactual = Treported n actual
3.64 3.33 4.52
1.0015 1.002 1.002 1.0000 1.003
1.0022 1.008 1.008 1.0037 1.0046
1.0029 1.016 1.016 1.0090 1.005
3.06
Table 31 Representative CPU Thermal Diode and Transistor Non-Ideality Factors CPU or ASIC Substrate Remote Diodes
A substrate diode is a parasitic PNP transistor that has its collector tied to ground through the substrate and the base (Remote -) and emitter (Remote +) brought out to pins. Connection to these pins is shown in Figure 13. The non-ideality figures in Table 31 include the effects of any package resistance and represent the value seen from the CPU socket. The temperature indicated will need to be compensated for the departure from a non-ideality of 1.008.
Remote +
where:
Treported = reported temperature in temperature register.
Tactual = actual remote diode temperature.
nactual = selected diode's non-ideality factor, nf . Temperatures are in Kelvins or C + 273.15.
CPU
Substrate
ASC7621
Remote -
This equation assumes that the series resistance of the remote diode is the same for each. This resistance is given in the data sheet for the CPU and may vary from 2.5 to 4.5.
Figure 13 CPU Remote Diode Connection
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ASC7621
Series Resistance
Any external series resistance in the connections from the ASC7621 to the CPU pins should be accounted for in interpreting the results of a measurement. The impact of series resistance on the measured temperature is a result of measurement currents developing offset voltages that add to the diode voltage. This is relatively constant with temperature and may be corrected with a fixed value in the offset register. To determine the temperature impact of resistance is as follows:
TR = RS x I D / TV or, TR = RS x 90A = RS x 0.391C / 230V / C
transistor's die temperature is usually not the temperature of interest and care must be taken to minimize the thermal resistance and physical distance between that temperature and the remote diode. The offset and response time will need to be characterized by the user.
Board Layout Considerations
The distance between the remote sensor and the ASC7621 should be minimized. All wiring should be defended from high frequency noise sources and a balanced differential layout maintained on Remote + and Remote -. Any noise, both common-mode and differential, induced in the remote diode interconnect may result in an offset in the temperature reported. Circuit board layout should follow the recommendation of Figure 15. Basically, use 10-mil lines and spaces with grounds on each side of the differential pair. Closer spacing may also be used if required by layout, but the priority is balance of diode path and minimum vias. Choose the ground plane closest to the CPU when using the CPU's remote diode. 10 mil Line 10 mil Space GND Remote + Remote GND
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
where:
TR = difference in the temperature reading from actual. RS = total series resistance of interconnect (both leads). I D = difference in the two diode current levels (90A). TV = scale of temperature vs. VBE (230V/C).
For example, a total series resistance of 10 would give an offset of +3.9C.
Discrete Remote Diodes
When sensing temperatures other than the CPU or GPU substrate, an NPN or PNP transistor may be used. Most commonly used are the 2N3904 and 2N3906. These have characteristics similar to the CPU substrate diode with non-ideality around 1.0046. They are connected with base to collector shorted as shown in Figure 14. While it is important to minimize the distance to the remote diode to reduce high-frequency noise pickup, they may be located many feet away with proper shielding. Shielded, twisted-pair cable is recommended, with the shield connected only at the ASC7621 end as close as possible to the ground pin of the device.
Remote +
Figure 15 Recommended Remote Diode Circuit Board Interconnect
Noise filtering is accomplished by using a bypass capacitor placed as close as possible to the two pairs of ASC7621 Remote + and Remote - pins. A 1.0nF ceramic capacitor is recommended, but up to 3.3nF may be used. Additional filtering takes place within the ASC7621. It is recommended that the following guidelines be used to minimize noise and achieve highest accuracy: 1. Place a 0.1F bypass capacitor to digital ground as close as possible to the power pin of the ASC7621. Match the trace routing of the Remote + and Remote - leads and use a 1.0nF filter capacitor close to the ASC7621. Use ground runs along side the pair to minimize differential coupling as in Figure 15. Place the ASC7621 as close to the CPU or GPU remote diode leads as possible to minimize noise and series resistance. Avoid running diode connections close to or in parallel with high-speed busses or 12V, staying at least 2cm away.
2N3906
ASC7621
Remote Remote +
2.
2N3904
ASC7621
Remote -
3.
Figure 14 Discrete Remote Diode Connection
As with the CPU substrate diode, the temperature reported will be subject to the same errors due to nonideality variation and series resistance. However, the
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ASC7621
5. 6. Avoid running diode connections close to on-board switching power supply inductors. PC board leakage should be minimized by maintaining minimum trace spacing and covering traces over their full length with solder mask. PC's fan and CPU diode to evaluate various settings under real operating conditions without the need to adjust BIOS code. After optimization, the settings may be programmed into the system. Features: * Interactive GUI for setting limits and operational configuration * aSC7512 and ASC7621 Automatic Fan Control * Powered and operated from the USB port * Support for reading or writing to any register * User-defined, time-stamped logging of any registers, saved in spreadsheet-compatible format * Graphical readouts: * Temperature and alarms * Fan RPM * Automatic fan control state * Voltage * Selectable on-board 2N3904 or wired remote diode * Headers for 2-, 3- and 4-wire fans with PWM for aSC7512 * Headers for 3 4-wire fans for ASC7621 * Saving of register setting configurations * LED indicators of pin alarm states * Optional use of external 12V fan power for higher current fans * Optional connection to off-board SMBus clients
Thermal Considerations
The temperature of the ASC7621 will be close to that of the PC board on which it is mounted. Conduction through the leads is the primary path for heat flow. The reported local sensor is very close to the circuit board temperature and typically between the board and ambient. In order to measure PC board temperature in an area of interest, such as the area around the CPU where voltage regulator components generate significant heat, a remote diode-connected transistor should be used. A surfacemount SOT-23 or SOT-223 is recommended. The small size is advantageous in minimizing response time because of its low thermal mass, but at the same time it has low surface area and a high thermal resistance to ambient air. A compromise must be achieved between minimizing thermal mass and increasing the surface area to lower the junction-to-ambient thermal resistance. In order to sense temperature of air-flows near boardmounted heat sources, such as memory modules, the sensor should be mounted above the PC board. A TO-92 packaged transistor is recommended. The power consumption of the ASC7621 is relatively low and should have little self-heating effect on the local sensor reading. At the highest measurement rate the dissipation is less than 2mW, resulting in only a few tenths of a degree rise.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Application Diagrams
The ASC7621 may be easily adapted to 2-, 3- or 4-wire fans for precise, wider-range fan speed control when compared to variable DC drive. Up to four fans may be controlled. Fans 1 and 2 are independent. Fan 3 is independent and may be tied to fan 4 for speed control. Separate tachometer readings may be reported for all four. Application diagram in Figure 16 shows connections to four 4-wire fans. External FETs may be added to the PWM output to drive 3-wire fans.
Evaluation Board
The Andigilog SMBus EVB provides a platform for evaluation of the operational characteristics of the aSC7511, aSC7512 and ASC7621. The board features a graphical user interface (GUI) to control and monitor all activities and readings of these parts. The provided software will run on a Windows XPTM-based desktop or laptop PC with a USB port. In addition to being a self-contained fan speed control demonstration, it may be connected into an operating
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ASC7621
12V 10K 15K REMOTE 1+ CPU
Substrate
1nF
REMOTE 1-
TACH 1 PWM 1
7.5K 0.01F 12V
2N3904 1nF
REMOTE 2 + REMOTE 2 -
Preliminary Specification - Subject to change without notice
10K 15K
Preliminary Specification - Subject to change without notice
TACH 2 PWM 2
7.5K 12V 10K 15K 0.01F
VCCP 2.5V 5V 12V 3.3V
VCCP 2.5V 5V ASC7621 12V 3.3V GND TACH 3 PWM 3
7.5K
0.1F 100pF
GPIO / Alerts PECI Vtt SMBus
GPIO1 GPIO2 GPIO3 PECI Vtt SMBDAT SMBCLK
0.01F 12V 10K 15K
TACH 4
7.5K
0.01F
Figure 16 Application Diagram
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ASC7621
Physical Dimensions
inches unless otherwise noted
24-Lead Molded QSOP Package
D X
0.010 E1 E 2 Pin 1 L e b
GAUGE PLANE SEATING PLANE
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
DETAIL "A"
0.015 0.004 x 45 A1 1 A
DETAIL "A" C
Notes: 1. 2. 3. 4. 5. Pb-Free Co-planarity is 0 to 0.004" MAX Package surface finish - Matte (VDI #24~27) All dimensions exclude mold flash The lead width, B, to be determined at 0.0075" from the lead tip
Symbol A A1 B D E1 E E C L X 1 2
MIN 0.054 0.004 0.008 0.337 0.150 0.229 0.0075 0.016 0
MAX 0.068 0.0098 0.012 0.344 0.157 0.244 0.0098 0.034 8 7 BSC
0.025 BSC
0.0325 REF
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ASC7621
Data Sheet Classifications
Preliminary Specification
This classification is shown on the heading of each page of a specification for products that are either under development (design and qualification), or in the formative planning stages. Andigilog reserves the right to change or discontinue these products without notice.
New Release Specification
This classification is shown on the heading of the first page only of a specification for products that are either under the later stages of development (characterization and qualification), or in the early weeks of release to production. Andigilog reserves the right to change the specification and information for these products without notice.
Preliminary Specification - Subject to change without notice
Preliminary Specification - Subject to change without notice
Fully Released Specification
Fully released datasheets do not contain any classification in the first page header. These documents contain specification on products that are in full production. Andigilog will not change any guaranteed limits without written notice to the customers. Obsolete datasheets that were written prior to January 1, 2001 without any header classification information should be considered as obsolete and non-active specifications, or in the best case as Preliminary Specifications.
PentiumTM is a trademark of Intel Corporation AthlonTM and DuronTM are trademarks of AMD Corporation SST and Simple Serial Transport are trademarks of Analog Devices, Inc. Windows XPTM is a trademark of Microsoft, Inc.
LIFE SUPPORT POLICY ANDIGILOG'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF ANDIGILOG, INC. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
Andigilog, Inc. 8380 S. Kyrene Rd., Suite 101 Tempe, Arizona 85284 Tel: (480) 940-6200 Fax: (480) 940-4255 (c) Andigilog, Inc. 2006 - 50 www.andigilog.com October 2006 - 70A06010

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