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STK17T88
nvTime Event Data Recorder 32K x 8 AutoStoreTM nvSRAM With Real-Time Clock
* Data Integrity of Simtek nvSRAM Combined with Full-Featured Real-Time Clock o Low Power, 300 nA Max, RTC current o Capacitor or battery backup for RTC * Watchdog Timer * Clock Alarm with programmable Interrupts * 25ns, 35ns and 45ns Access Times * "Hands-off" Automatic STORE on Power Down with only a small capacitor * STORE to QuantumTrapTM Initiated by Software , device pin, or on Power Down * RECALL to SRAM Initiated by Software or Power Up * Unlimited READ, WRITE and RECALL Cycles * High-reliability o Endurance to 1 Million Cycles o Retention to 100 years at 125 C * 5mA Typical ICC at 200ns Cycle Time * Single 3V +20%, -10% Operation * SSOP and DIP Packages, (ROHS compliant)
TM
FEATURES
DESCRIPTION
The Simtek STK17T88 combines a 256 Kbit nonvolatile static RAM with a full-featured real-time clock in a reliable, monolithic integrated circuit. The embedded nonvolatile elements incorporate Simtek's QuantumTrapTM technology producing the world's most reliable nonvolatile memory. The SRAM can be read and written an unlimited number of times, while independent, nonvolatile data resides in the nonvolatile elements. The Real-Time Clock function provides an accurate clock with leap year tracking and a programmable, high accuracy oscillator. The Alarm function is programmable for one-time alarms or periodic seconds, minutes, hours, or days. There is also a programmable Watchdog Timer for process control.
BLOCK DIAGRAM
Quantum Trap 512 X 512 A5 A6 A7 A8 A9 A11 A12 A13 A14 DQ0 DQ1 DQ2 DQ3 DQ4 DQ5 DQ6 DQ7 ROW DECODER STORE STATIC RAM ARRAY 512 X 512 RECALL VCC VCAP VRTCbat VRTCcap
POWER CONTROL STORE/ RECALL CONTROL
HSB
SOFTWARE DETECT INPUT BUFFERS COLUMN I/O COLUMN DEC RTC
A13 - A0
X1 X2 INT A14 - A0
G E W
A 0 A 1 A 2 A 3 A 4 A10 MUX
Figure 1. Block Diagram
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PACKAGES
VCAP A14 A12 A7 A6 A5 INT A4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 VCC VCAP HSB W A13 A8 A9 A11 A14 A12 A7 A6 A5 INT A4 VSS VRTCbat DQ0 A3 A2 A1 A0 DQ1 DQ2 X1 X2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 VCC HSB W A13 A8 A9 A11 VSS G A10 E DQ7 DQ6 VRTCcap DQ5 DQ4 DQ3 VCC
48 Pin SSOP
VSS VRTCbat DQ0 A3 A2 A1 A0 DQ1 DQ2 X1 X2
VSS VRTCcap DQ6 G A10 E DQ7 DQ5 DQ4 DQ3 VCC
40 Pin PDIP
48 Pin SSOP
Relative PCB area usage. See website for detailed package size specifications.
PIN DESCRIPTIONS
Pin Name
A14 - A0 DQ7 -DQ0 E Input I/O Input
I/O
Description
Address: The 15 address inputs select one of 32,752 bytes in the nvSRAM array or one of 16 bytes in the clock register map. Data: Bi-directional 8-bit data bus for accessing the nvSRAM array and RTC. Chip Enable: The active low E input selects the device.
W
Input
Write Enable: The active low W enables data on the DQ pins to be written to the address location latched by the falling edge of E .
G X1 X2 VRTCcap VRTCbat VCC HSB INT VCAP VSS (Blank)
Input Output Input Power Supply Power Supply Power Supply I/O Output Power Supply Power Supply No Connect
Output Enable: The active low G input enables the data output buffers during read cycles. De-asserting G high causes the DQ pins to tri-state. Crystal Connection, drives crystal on startup. Crystal Connection for 32.768 kHz crystal. Capacitor supplied backup RTC supply voltage. (Left unconnected if VRTCbat is used.) Battery supplied backup RTC supply voltage. (Left unconnected if VRTCcap is used.) Power 3.0V +20%, -10% Hardware Store Busy: When low this output indicates a Hardware Store is in progress. When pulled low external to the chip it will initiate a nonvolatile STORE operation. A weak internal pull up resistor keeps this pin high if not connected. (Connection Optional) Interrupt Output: Can be programmed to respond to the clock alarm, the watchdog timer and the power monitor. Programmable to either active high (push/pull) or active low (open-drain). Autostore Capacitor: Supplies power to nvSRAM during power loss to store data from SRAM to nonvolatile elements. Ground Unlabeled pins have no internal connection.
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STK17T88 ABSOLUTE MAXIMUM RATINGSa
-0.5V to +4.1V Power Supply Voltage -0.5V to (VCC + 0.5V) Voltage on Input Relative to VSS -0.5V to (VCC + 0.5V) Voltage on Outputs Temperature under Bias -55C to 125C Junction Temperature -55C to 140C Storage Temperature -65C to 150C Power Dissipation 1W DC Output Current (1 output at a time, 1s duration) 15mA
Notes a: Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only, and functional operation of the device at conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Package Thermal Characteristics see website: http://www.simtek.com/
DC CHARACTERISTICS
Symbol
ICC1
Parameter
Average VCC Current
Commercial MIN MAX
65 55 50
Industrial MIN MAX
70 60 55
Units
mA mA mA
Notes
tAVAV = 25ns tAVAV = 35ns tAVAV = 45ns Dependent on output loading and cycle rate. Values obtained without output loads. All Inputs Don't Care, VCC = max Average current for duration of STORE cycle (tSTORE). W (VCC - 0.2V) All Others Inputs Cycling, at CMOS Levels. Dependent on output loading and cycle rate. Values obtained without output loads. All Inputs Don't Care Average current for duration of STORE cycle (tSTORE). E (VCC - 0.2V) All Others VIN 0.2V or (VCC - 0.2V) Standby current level after nonvolatile cycle is complete. VCC = max
ICC2
Average VCC Current during STORE Average VCC Current at tAVAV = 200ns
3
3
mA
ICC3
3V, 25C, Typical Average VCAP Current during AutoStoreTM Cycle VCC Standby Current
5 3
5 3
mA mA
ICC4
ISB
(Standby, Stable CMOS Input Levels)
2
2
mA
IILK IOLK VIH VIL VOH VOL TA VCC VCAP
Input Leakage Current 1 Off-State Output Leakage Current 1 Input Logic "1" Voltage Input Logic "0" Voltage Output Logic "1" Voltage Output Logic "0" Voltage Operating Temperature Operating Voltage Storage Capacitor 0 2.7 17 2.0 VSS - 0.5 2.4 0.4 70 3.6 57 -40 2.7 17 VCC + 0.3 0.8 2.0 VSS - 0.5 2.4 0.4 85 3.6 57 1 VCC + 0.3 0.8 A V V V V
o
1
A
VIN = VSS to VCC VCC = max VIN = VSS to VCC, E or G VIH All Inputs All Inputs IOUT = -2mA IOUT = 4mA
C 3.0V +20%, -10% Between Vcap pin and Vss, 6.3V rated.
V F
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AC TEST CONDITIONS
0V to 3V Input Pulse Levels Input Rise and Fall Times 5ns Input and Output Timing Reference Levels 1.5V Output Load See Figure 2 and Figure 3
CAPACITANCE
SYMBOL CIN COUT
Notes
b
(TA = 25C, f = 1.0MHz)
MAX 7 7 UNITS pF pF CONDITIONS V = 0 to 3V V = 0 to 3V
PARAMETER Input Capacitance Output Capacitance
b: These parameters are guaranteed but not tested
3.0V 577 Ohms
OUTPUT 789 Ohms OUTPUT
3.0V 577 Ohms
30 pF INCLUDING SCOPE AND FIXTURE
789 Ohms
5 pF 30 pF INCLUDING SCOPE AND FIXTURE
Figure 2. AC Output Loading
Figure 3. AC Output Loading, for tristate specs ( tHZ, tLZ, tWLQZ, tWHQZ, tGLQX, tGHQZ )
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RTC DC CHARACTERISTICS
Symbol
IBAK VRTCbat VRTCcap tOSCS
Parameter
RTC Backup Current RTC Battery Pin Voltage RTC Capacitor Pin Voltage RTC Oscillator time to start
Commercial
MIN MAX
300 3.3 2.7 1 10
Industrial
MIN MAX
350 3.3 2.7 1 10
Units
nA V V min sec
Notes
From either VRTCcap or VRTCbat Typical = 3.0 Volts during normal operation Typical = 2.4 Volts during normal operation @ MIN Temperature from Power up or Enable @25C from Power up or Enable
1.8 1.2
1.8 1.2
-
-
RTC RECOMMENDED COMPONENT CONFIGURATION
C1 RF C2
Y1
X1 X2
Recommended Values Y1 = 32.768 KHz RF = 10M Ohm C1 = 2.2 pF C2 = 47 pF
Figure 4. RTC COMPONENT CONFIGURATION
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SRAM READ CYCLES #1 & #2
SYMBOLS NO. #1 1 2 3 4 5 6 7 8 9 10 11
d tAXQX
STK17T88-25 PARAMETER Alt. tACS tRC tAA Chip Enable Access Time Read Cycle Time Address Access Time Output Enable to Data Valid Output Hold after Address Change Chip Enable to Output Active Chip Disable to Output Inactive Output Enable to Output Active Output Disable to Output Inactive Chip Enable to Power Active Chip Disable to Power Standby 0 25 0 10 3 3 10 25 25 12 MIN MAX 25
STK17T88-35 MIN MAX 35 35 35 15 3 3 13 0 13 0 35
STK17T88-45 UNITS MIN MAX 45 45 45 20 3 3 15 0 15 0 45 ns ns ns ns ns ns ns ns ns ns ns
#2 tELQV
tAVAV
c d
tAVAVc
tAVQV
tGLQV
tOE tOH
tELQX tEHQZ
e
tLZ tHZ tOLZ
e
tGLQX tGHQZ
tOHZ tPA tPS
tELICCb tEHICC
b
Notes c: W must be high during SRAM READ cycles d: Device is continuously selected with E and G both low e: Measured 200mV from steady state output voltage f: HSB must remain high during READ and WRITE cycles.
SRAM READ CYCLE #1: Address Controlledc,d,f
2 tAVAV
ADDRESS
5 tAXQX 3 tAVQV
DATA VALID
DQ (DATA OUT)
SRAM READ CYCLE #2: E Controlledc,f
2 tAVAV
ADDRESS
6 tELQX 7 tEHQZ 1 tELQV 11 tEHICCL
E
G
4 8 tGLQX 10 tELICCH ICC
STANDBY ACTIVE
tGLQV
9 tGHQZ
DQ (DATA OUT)
DATA VALID
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SRAM WRITE CYCLES #1 & #2
NO. #1 12 13 14 15 16 17 18 19 20 21 tAVAV tWLWH tELWH tDVWH tWHDX tAVWH tAVWL tWHAX tWLQZe,g tWHQX SYMBOLS #2 tAVAV tWLEH tELEH tDVEH tEHDX tAVEH tAVEL tEHAX Alt. tWC tWP tCW tDW tDH tAW tAS tWR tWZ tOW
Write Cycle Time Write Pulse Width Chip Enable to End of Write Data Set-up to End of Write Data Hold after End of Write Address Set-up to End of Write Address Set-up to Start of Write Address Hold after End of Write Write Enable to Output Disable Output Active after End of Write
PARAMETER
STK17T88-25 MIN 25 20 20 10 0 20 0 0 10 3 MAX
STK17T88-35 MIN 35 25 25 12 0 25 0 0 13 3 MAX
STK17T88-45 MIN 45 30 30 15 0 30 0 0 15 3 MAX
UNITS
ns ns ns ns ns ns ns ns ns ns
Notes g: If W is low when E goes low, the outputs remain in the high-impedance state. h: E or W must be VIH during address transitions.
SRAM WRITE CYCLE #1: W Controlledh,f
12 tAVAV
ADDRESS
14 tELWH 19 tWHAX
E
17 tAVWH 13 tWLWH 15 tDVWH 16 tWHDX
18 tAVWL
W
DATA IN
20 tWLQZ
DATA VALID
DATA OUT
PREVIOUS DATA
HIGH IMPEDANCE
21 tWHQX
SRAM WRITE CYCLE #2: E Controlledh,f
12 tAVAV
ADDRESS
18 tAVEL 14 tELEH 19 tEHAX
E
17 tAVEH
W
13 tWLEH 15 tDVEH 16 tEHDX
DATA VALID HIGH IMPEDANCE
DATA IN DATA OUT
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MODE SELECTION
E H L L W X H L G X L X A13 - A0 X X X 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x03F8 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x07F0 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x0FC0 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x0C63 MODE Not Selected Read SRAM Write SRAM Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Autostore Disable Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Autostore Enable Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Nonvolatile Store Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Nonvolatile Recall I/O Output High Z Output Data Input Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output Data Output High Z Output Data Output Data Output Data Output Data Output Data Output High Z POWER Standby Active Active NOTES
L
H
L
Active
i, j, k
L
H
L
Active
i, j, k
Active i, j, k ICC2
L
H
L
L
H
L
Active
i, j, k
Notes i: The six consecutive addresses must be in the order listed. W must be high during all six consecutive cycles to enable a nonvolatile cycle. j: While there are 15 addresses on the STK17T88, only the lower 14 are used to control software modes k: I/O state depends on the state of G . The I/O table shown assumes G low.
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AutoStoreTM /POWER-UP RECALL
SYMBOLS NO. Standard 22 23 24 25 tHRECALL tSTORE VSWITCH tVCCRISE tHLHZ Alternate Power-up RECALL Duration STORE Cycle Duration Low Voltage Trigger Level 2.55 150 MIN MAX 20 12.5 2.65 ms ms V s l m PARAMETER STK17T88 UNITS NOTES
VCC Rise Time Notes l: tHRECALL starts from the time VCC rises above VSWITCH m: If an SRAM WRITE has not taken place since the last nonvolatile cycle, no STORE will take place
AutoStoreTM/POWER-UP RECALL
VCC 24 VSWITCH
STORE occurs only if a SRAM write has happened.
No STORE occurs without at least one SRAM write.
25 tVCCRISE
AutoStoreTM
23 tSTORE
23 tSTORE
POWER-UP RECALL
22 tHRECALL
22 tHRECALL
Read & Write Inhibited
POWER-UP RECALL
BROWN OUT TM AutoStore
POWER-UP RECALL
POWER DOWN TM AutoStore
Note: Read and Write cycles will be ignored during STORE, RECALL and while VCC is below VSWITCH.
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SOFTWARE-CONTROLLED STORE/RECALL CYCLEn,o
SYMBOLS NO. E cont 26 27 28 29 tAVAV tAVEL tELEH tELAX G cont tAVAV tAVGL tGLGH tGLAX tRC tAS tCW STORE/RECALL Initiation Cycle Time Address Set-up Time Clock Pulse Width Address Hold Time 25 0 20 20 35 0 25 20 40 45 0 30 20 40 ns ns ns ns s o PARAMETER Alt. MIN MAX MIN MAX MIN MAX STK17T88-25 STK17T88-35 STK17T88-45 UNITS NOTES
30 tRECALL tRECALL 40 RECALL Duration Notes n: The software sequence is clocked with E controlled READs or G controlled READs. o: The six consecutive addresses must be read in the order listed in the Mode Selection Table. W
must be high during all six consecutive cycles.
SOFTWARE STORE/RECALL CYCLE: E Controlledo
26 tAVAV ADDRESS 27 tAVEL
ADDRESS #1
26 tAVAV
ADDRESS #6
E
28 tELEH
G
29 tELAX
23 tSTORE DQ (DATA)
DATA VALID DATA VALID
/
30 tRECALL
HIGH IMPEDENCE
SOFTWARE STORE/RECALL CYCLE: G Controlledo
26 tAVAV ADDRESS
ADDRESS #1
26 tAVAV
ADDRESS #6
E
27 tAVGL
28 tGLGH
G
29 tGLAX DQ (DATA)
DATA VALID DATA VALID
23 tSTORE
/
30 tRECALL
HIGH IMPEDENCE
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HARDWARE STORE CYCLE
SYMBOLS NO. Standard 31 32 tDELAY tHLHX Alternate tHLQZ Time Allowed to Complete SRAM Cycle Hardware STORE Pulse Width PARAMETER MIN 1 15 300 MAX s ns ns p STK17T88 UNITS NOTES
tHLBL Hardware STORE Low to STORE Busy 33 Notes p: Read and Write cycles in progress before HSB is asserted are given this amount of time to complete.
HARDWARE STORE CYCLE
32 tHLHX
HSB (IN)
23 tSTORE
HSB (OUT)
33 tHLBL
HIGH IMPEDENCE
HIGH IMPEDENCE
31 tDELAY DQ (DATA OUT)
DATA VALID DATA VALID
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DEVICE OPERATION
nvSRAM
The STK17T88 nvSRAM is made up of two functional components paired in the same physical cell. These are a SRAM memory cell and a nonvolatile QuantumTrapTM cell. The SRAM memory cell operates as a standard fast static RAM. Data in the SRAM can be transferred to the nonvolatile cell (the STORE operation), or from the nonvolatile cell to SRAM (the RECALL operation). This unique architecture allows all cells to be stored and recalled in parallel. During the STORE and RECALL operations SRAM READ and WRITE operations are inhibited. The STK17T88 supports unlimited reads and writes just like a typical SRAM. In addition, it provides unlimited RECALL operations from the nonvolatile cells and up to 1 million STORE operations.
SRAM WRITE
A WRITE cycle is performed whenever E and W are low and HSB is high. The address inputs must be stable prior to entering the WRITE cycle and must remain stable until either E or W goes high at the end of the cycle. The data on the common I/O pins DQ0-7 will be written into the memory if it is valid tDVWH before the end of a W controlled WRITE or tDVEH before the end of an E controlled WRITE. It is recommended that G be kept high during the entire WRITE cycle to avoid data bus contention on common I/O lines. If G is left low, internal circuitry will turn off the output buffers tWLQZ after W goes low.
AutoStoreTM OPERATION
The STK17T88 stores data to nvSRAM using one of three storage operations. These three operations are Hardware Store, activated by HSB , Software Store, actived by an address sequence, and AutoStoreTM, on device power down. AutoStoreTM operation is a unique feature of Simtek QuantumTrapTM technology and is enabled by default on the STK17T88. During normal operation, the device will draw current from Vcc to charge a capacitor connected to the Vcap pin. This stored charge will be used by the chip to perform a single STORE operation. If the voltage on the Vcc pin drops below Vswitch, the part will automatically disconnect the Vcap pin from Vcc. A STORE operation will be initiated with power provided by the Vcap capacitor. Figure 5 shows the proper connection of the storage capacitor (Vcap) for automatic store operation. Refer to the DC CHARACTERISTICS table for the size of Vcap. The voltage on the Vcap pin is driven to 5V by a charge pump internal to the chip. A pull up should be placed on W to hold it inactive during power up. To reduce unneeded nonvolatile stores, AutoStoreTM and Hardware Store operations will be ignored unless at least one WRITE operation has taken place since the most recent STORE or RECALL cycle. Software initiated STORE cycles are performed regardless of whether a WRITE operation has taken place. The HSB signal can be monitored by the system to detect an AutoStoreTM cycle is in progress.
SRAM READ
The STK17T88 performs a READ cycle whenever E and G are low while W and HSB are high. The address specified on pins A14-0 determines which of the 32,752 data bytes will be accessed. When the READ is initiated by an address transition, the outputs will be valid after a delay of tAVQV (READ cycle #1). If the READ is initiated by E or G , the outputs will be valid at tELQV or at tGLQV, whichever is later (READ cycle #2). The data outputs will repeatedly respond to address changes within the tAVQV access time without the need for transitions on any control input pins, and will remain valid until another address change or until E or G is brought high, or W or HSB is brought low.
VCC VCAP VCC
10k Ohm
VCAP
W
Figure 5: AutoStoreTM Mode
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HARDWARE STORE ( HSB ) OPERATION
The STK17T88 provides the HSB pin for controlling and acknowledging the STORE operations. The HSB pin can be used to request a hardware STORE cycle. When the HSB pin is driven low, the STK17T88 will conditionally initiate a STORE operation after tDELAY. An actual STORE cycle will only begin if a WRITE to the SRAM took place since the last STORE or RECALL cycle. The HSB pin also acts as an open drain driver that is internally driven low to indicate a busy condition while the STORE (initiated by any means) is in progress. SRAM READ and WRITE operations that are in progress when HSB is driven low by any means are given time to complete before the STORE operation is initiated. After HSB goes low, the STK17T88 will continue SRAM operations for tDELAY. During tDELAY, multiple SRAM READ operations may take place. If a WRITE is in progress when HSB is pulled low it will be allowed a time, tDELAY, to complete. However, any SRAM WRITE cycles requested after HSB goes low will be inhibited until HSB returns high. During any STORE operation, regardless of how it was initiated, the STK17T88 will continue to drive the HSB pin low, releasing it only when the STORE is complete. Upon completion of the STORE operation the STK17T88 will remain disabled until the HSB pin returns high. If
HSB
SOFTWARE STORE
Data can be transferred from the SRAM to the nonvolatile memory by a software address sequence. The STK17T88 software STORE cycle is initiated by executing sequential E controlled READ cycles from six specific address locations in exact order. During the STORE cycle an erase of the previous nonvolatile data is first performed, followed by a program of the nonvolatile elements. Once a STORE cycle is initiated, further input and output are disabled until the cycle is completed. Because a sequence of READs from specific addresses is used for STORE initiation, it is important that no other READ or WRITE accesses intervene in the sequence, or the sequence will be aborted and no STORE or RECALL will take place. To initiate the software STORE cycle, the following READ sequence must be performed:
1. 2. 3. 4. 5. 6. Read address Read address Read address Read address Read address Read address 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x0FC0 Valid READ Valid READ Valid READ Valid READ Valid READ Initiate STORE cycle
The software sequence may be clocked with controlled READs or G controlled READs.
E
is not used, it should be left unconnected.
HARDWARE RECALL (POWER-UP)
During power up, or after any low-power condition (VCC < VSWITCH), an internal RECALL request will be latched. When VCC once again exceeds the sense voltage of VSWITCH, a RECALL cycle will automatically be initiated and will take tHRECALL to complete.
Once the sixth address in the sequence has been entered, the STORE cycle will commence and the chip will be disabled. It is important that READ cycles and not WRITE cycles be used in the sequence, although it is not necessary that G be low for the sequence to be valid. After the tSTORE cycle time has been fulfilled, the SRAM will again be activated for READ and WRITE operation.
SOFTWARE RECALL
Data can be transferred from the nonvolatile memory to the SRAM by a software address sequence. A software RECALL cycle is initiated with a sequence of READ operations in a manner similar to the software STORE initiation. To initiate the RECALL cycle, the following sequence of E controlled READ operations must be performed:
1. 2. 3. 4. 5. 6. Read address Read address Read address Read address Read address Read address 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x0C63 Valid READ Valid READ Valid READ Valid READ Valid READ Initiate RECALL cycle
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Internally, RECALL is a two-step procedure. First, the SRAM data is cleared, and second, the nonvolatile information is transferred into the SRAM cells. After the tRECALL cycle time the SRAM will once again be ready for READ and WRITE operations. The RECALL operation in no way alters the data in the nonvolatile elements.
NOISE CONSIDERATIONS
The STK17T88 is a high-speed memory and so must have a high-frequency bypass capacitor of approximately 0.1F connected between VCC and VSS, using leads and traces that are as short as possible. As with all high-speed CMOS ICs, careful routing of power, ground and signals will reduce circuit noise.
PREVENTING AUTOSTORETM
The AutoStoreTM function can be disabled by initiating an AutoStore Disable sequence. A sequence of read operations is performed in a manner similar to the software STORE initiation. To initiate the AutoStore Disable sequence, the following sequence of E controlled read operations must be performed:
1. 2. 3. 4. 5. 6. Read address Read address Read address Read address Read address Read address 0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x03F8 Valid READ Valid READ Valid READ Valid READ Valid READ AutoStore Disable
LOW AVERAGE ACTIVE POWER
CMOS technology provides the STK17T88 this the benefit of drawing significantly less current when it is cycled at times longer than 50ns. Figure 6 shows the relationship between ICC and READ/WRITE cycle time. Worst-case current consumption is shown for commercial temperature range, VCC = 3.6V, and chip enable at maximum frequency. Only standby current is drawn when the chip is disabled. The overall average current drawn by the STK17T88 depends on the following items: 1. 2. 3. 4. 5. 6. The duty cycle of chip enable. The overall cycle rate for accesses. The ratio of READs to WRITEs. The operating temperature. The VCC level. I/O loading.
The AutoStoreTM can be re-enabled by initiating an AutoStore Enable sequence. A sequence of read operations is performed in a manner similar to the software RECALL initiation. To initiate the AutoStore Enable sequence, the following sequence of E controlled read operations must be performed:
Average Active Current (mA)
1. 2. 3. 4. 5. 6.
Read address Read address Read address Read address Read address Read address
0x0E38 0x31C7 0x03E0 0x3C1F 0x303F 0x07F0
Valid READ Valid READ Valid READ Valid READ Valid READ AutoStore Enable
50 40 30 20 10 0 50 100 150 200 300 Cycle Time (ns)
Writes
If the AutoStoreTM function is disabled or re-enabled a manual STORE operation (Hardware or Software) needs to be issued to save the AutoStore state through subsequent power down cycles. The part comes from the factory with AutoStoreTM enabled.
DATA PROTECTION
The STK17T88 protects data from corruption during low-voltage conditions by inhibiting all externally initiated STORE and WRITE operations. The lowvoltage condition is detected when VCC < VSWITCH . If the STK17T88 is in a WRITE mode (both E and W low ) at power-up, after a RECALL, or after a STORE, the WRITE will be inhibited until a negative transition on E or W is detected. This protects against inadvertent writes during power up or brown out conditions.
Reads
Figure 6 Current vs. Cycle time
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REAL TIME CLOCK OPERATION
nvTIME OPERATION
The STK17T88 offers internal registers that contain Clock, Alarm, Watchdog, Interrupt, and Control functions. Internal double buffering of the clock and the clock/timer information registers prevents accessing transitional internal clock data during a read or write operation. Double buffering also circumvents disrupting normal timing counts or clock accuracy of the internal clock while accessing clock data. Clock and Alarm Registers store data in BCD format.
SETTING THE CLOCK
Setting the write bit "W" (in the flags register at 0x7FF0) to a "1" halts updates to the STK17T88 registers. The correct day, date and time can then be written into the registers in 24-hour BCD format. The time written is referred to as the "Base Time." This value is stored in nonvolatile registers and used in calculation of the current time. Resetting the write bit to "0" transfers those values to the actual clock counters, after which the clock resumes normal operation.
CLOCK OPERATIONS
The clock registers maintain time up to 9,999 years in one second increments. The user can set the time to any calendar time and the clock automatically keeps track of days of the week and month, leap years and century transitions. There are eight registers dedicated to the clock functions which are used to set time with a write cycle and to read time during a read cycle. These registers contain the Time of Day in BCD format. Bits defined as "X" are currently not used and are reserved for future use by Simtek.
BACKUP POWER
The RTC in the STK17T88 is intended for permanently powered operation. Either the VRTCcap or VRTCbat pin is connected depending on whether a capacitor or battery is chosen for the application. When primary power, Vcc, fails and drops below Vswitch the device will switch to the backup power supply. The clock oscillator uses very little current, which maximizes the backup time available from the backup source. Regardless of clock operation with the primary source removed, the data stored in nvSRAM is secure, having been stored in the nonvolatile elements as power was lost. Factors to be considered when choosing a backup power source include: the expected duration of power outages and the cost trade-off of using a battery versus a capacitor. During backup operation the STK17T88 consumes a maximum of 300 nanoamps at 2 volts. Capacitor or battery values should be chosen according to the application. Backup time values based on maximum current specs are shown below. Nominal times are approximately 3 times longer.
Capacitor Value 0.1 F 0.47 F 1.0 F 72 hours 14 days 30 days Backup Time
READING THE CLOCK
While the double-buffered RTC register structure reduces the chance of reading incorrect data from the clock, the user should halt internal updates to the STK17T88 clock registers before reading clock data to prevent the reading of data in transition. Stopping the internal register updates does not affect clock accuracy. The updating process is stopped by writing a "1" to the read bit "R" (in the flags register at 0x7FF0), and will not restart until a "0" is written to the read bit. The RTC registers can then be read while the internal clock continues to run. Within 20ms after a "0" is written to the read bit, all STK17T88 registers are simultaneously updated.
Using a capacitor has the obvious advantage of recharging the backup source each time the system is powered up.
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If a battery is used, a 3V lithium is recommended and the STK17T88 will only source current from the battery when the primary power is removed. The battery will not, however, be recharged at any time by the STK17T88. The battery capacity should be chosen for total anticipated cumulative down-time required over the life of the system. calibration circuit adds or subtracts counts from the oscillator divider circuit. The number of times pulses are suppressed (subtracted, negative calibration) or split (added, positive calibration) depends upon the value loaded into the five calibration bits found in calibration register at 0x7FF8. Adding counts speeds the clock up; subtracting counts slows the clock down. The Calibration bits occupy the five lower order bits in the control register 8. These bits can be set to represent any value between 0 and 31 in binary form. Bit D5 is a Sign bit, where a "1" indicates positive calibration and a "0" indicates negative calibration. Calibration occurs within a 64 minute cycle. The first 62 minutes in the cycle may, once per minute, have one second either shortened by 128 or lengthened by 256 oscillator cycles. If a binary "1" is loaded into the register, only the first 2 minutes of the 64 minute cycle will be modified; if a binary 6 is loaded, the first 12 will be affected, and so on. Therefore each calibration step has the effect of adding 512 or subtracting 256 oscillator cycles for every 125,829,120 actual oscillator cycles. That is +4.068 or -2.034 ppm of adjustment per calibration step in the calibration register. In order to determine how to set the calibration one may set the CAL bit in the flags register at 0x7FF0 to 1, which causes the INT pin to toggle at a nominal 512 Hz. Any deviation measured from the 512 Hz will indicate the degree and direction of the required correction. For example, a reading of 512.010124 Hz would indicate a +20 ppm error, requiring a -10 (001010) to be loaded into the Calibration register. Note that setting or changing the calibration register does not affect the frequency test output frequency.
STOPPING AND STARTING THE OSCILLATOR
The OSCEN bit in calibration register at 0x7FF8 controls the starting and stopping of the oscillator. This bit is nonvolatile and shipped to customers in the "enabled" (set to 0) state. To preserve battery life while system is in storage OSCEN should be set to a 1. This will turn off the oscillator circuit extending the battery life. If the OSCEN bit goes from disabled to enabled, it will take approximately 5 seconds (10 seconds max) for the oscillator to start. The STK17T88 has the ability to detect oscillator failure. This is recorded in the OSCF (Oscillator Failed bit) of the flags register at address 0x7FF0. When the device is powered on (VCC goes above Vswitch) the OSCEN bit is checked for "enabled" status. If the OSCEN bit is enabled and the oscillator is not active, the OSCF bit is set. The user should check for this condition and then write a 0 to clear the flag. It should be noted that in addition to setting the OSCF flag bit, the time registers are reset to the "Base Time" (see the section "Setting the Clock"), which is the value last written to the timekeeping registers. The Control/Calibration register and the OSCEN bit are not affected by the oscillator failed condition. If the voltage on the backup supply (either VRTCcap or VRTCbat) falls below their respective minimum level the oscillator may fail, leading to the oscillator failed condition which can be detected when system power is restored. The value of OSCF should be reset to 0 when the time registers are written for the first time. This will initialize the state of this bit which may have become set when the system was first powered on.
ALARM
The alarm function compares user-programmed values to the corresponding time-of-day values. When a match occurs, the alarm event occurs. The alarm drives an internal flag, AF, and may drive the INT pin if desired. There are four alarm match fields. They are date, hours, minutes and seconds. Each of these fields also has a Match bit that is used to determine if the field is used in the alarm match logic. Setting the Match bit to "0" indicates that the corresponding field will be used in the match process. Depending on the Match bits, the alarm can occur as specifically as one particular second on one day of the month, or as frequently as once per second
CALIBRATING THE CLOCK
The RTC is driven by a quartz controlled oscillator with a nominal frequency of 32.768 KHz. Clock accuracy will depend on the quality of the crystal, usually specified to 35 ppm limits at 25C. This error could equate to + 1.53 minutes per month. The STK17T88 employs a calibration circuit that can improve the accuracy to +1/-2 ppm at 25C. The
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continuously. The MSB of each alarm register is a Match bit. Selecting none of the Match bits (all 1's) indicates that no match is required. The alarm occurs every second. Setting the match select bit for seconds to "0" causes the logic to match the seconds alarm value to the current time of day. Since a match will occur for only one value per minute, the alarm occurs once per minute. Likewise, setting the seconds and minutes Match bits causes an exact match of these values. Thus, an alarm will occur once per hour. Setting seconds, minutes and hours causes a match once per day. Lastly, selecting all match values causes an exact time and date match. Selecting other bit combinations will not produce meaningful results; however the alarm circuit should follow the functions described. There are two ways a user can detect an alarm event, by reading the AF flag or monitoring the INT pin. The AF flag in the flags register at 0x7FF0 will indicate that a date/time match has occurred. The AF bit will be set to 1 when a match occurs. Reading the Flags/Control register clears the alarm flag bit (and all others). A hardware interrupt pin may also be used to detect an alarm event. set the WDS bit without concern that the watchdog timer value will be modified. A logical diagram of the watchdog timer is shown below. Note that setting the watchdog time-out value to 0 would be otherwise meaningless and therefore disables the watchdog function.
Oscillator 32.768KH2 Clock Divider 32 Hz Counter Zero Compare WDF
1 Hz
WDS
DQ Q
Load Register
WDW
write to Watchdog Register
Watchdog Register
Figure 7. Watchdog Timer Block Diagram
WATCHDOG TIMER
The watchdog timer is a free running down counter that uses the 32 Hz clock (31.25 ms) derived from the crystal oscillator. The oscillator must be running for the watchdog to function. It begins counting down from the value loaded in the Watchdog Timer register. The counter consists of a loadable register and a free running counter. On power up, the watchdog time-out value in register 0x7FF7 is loaded into the counter load register. Counting begins on power up and restarts from the loadable value any time the Watchdog Strobe (WDS) bit is set to 1. The counter is compared to the terminal value of 0. If the counter reaches this value, it causes an internal flag and an optional interrupt output. The user can prevent the time-out interrupt by setting WDS bit to 1 prior to the counter reaching 0. This causes the counter to be reloaded with the watchdog time-out value and to be restarted. As long as the user sets the WDS bit prior to the counter reaching the terminal value, the interrupt and flag never occurs. New time-out values can be written by setting the watchdog write bit to 0. When the WDW is 0 (from the previous operation), new writes to the watchdog timeout value bits D5-D0 allow the time-out value to be modified. When WDW is a 1, then writes to bits D5-D0 will be ignored. The WDW function allows a user to
The output of the watchdog timer is a flag bit WDF that is set if the watchdog is allowed to time-out. The flag is set upon a watchdog time-out and cleared when the Flags/Control register is read by the user. The user can also enable an optional interrupt source to drive the INT pin if the watchdog time-out occurs.
POWER MONITOR
The STK17T88 provides a power management scheme with power-fail interrupt capability. It also controls the internal switch to backup power for the clock and protects the memory from low-VCC access. The power monitor is based on an internal band-gap reference circuit that compares the VCC voltage to various thresholds. As described in the AutoStoreTM section previously, when Vswitch is reached as VCC decays from power loss, a data store operation is initiated from SRAM to the nonvolatile elements, securing the last SRAM data state. Power is also switched from VCC to the backup supply (battery or capacitor) to operate the RTC oscillator. When operating from the backup source no data may be read or written and the clock functions are not available to the user. The clock continues to operate in the background. Updated clock data is available to
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the user after tHRECALL delay (See AutoStoreTM /POWER-UP RECALL) after VCC has been restored to the device. According to the programming selections, the pin can be driven in the backup mode for an alarm interrupt. In addition, the pin can be an active low (open-drain) or an active high (push-pull) driver. If programmed for operation during backup mode, it can only be active low. Lastly, the pin can provide a one-shot function so that the active condition is a pulse or a level condition. In one-shot mode, the pulse width is internally fixed at approximately 200 ms. This mode is intended to reset a host microcontroller. In level mode, the pin goes to its active polarity until the Flags/Control register is read by the user. This mode is intended to be used as an interrupt to a host microcontroller. The control bits are summarized as follows: Watchdog Interrupt Enable - WIE. When set to 1, the watchdog timer drives the INT pin as well as an internal flag when a watchdog time-out occurs. When WIE is set to 0, the watchdog timer affects only the internal flag. Alarm Interrupt Enable - AIE. When set to 1, the alarm match drives the INT pin as well as an internal flag. When set to 0, the alarm match only affects to internal flag.
INT VSS
INTERRUPTS
The STK17T88 provides three potential interrupt sources. They include the watchdog timer, the power monitor, and the clock/calendar alarm. Each can be individually enabled and assigned to drive the INT pin. In addition, each has an associated flag bit that the host processor can use to determine the cause of the interrupt. Some of the sources have additional control bits that determine functional behavior. In addition, the pin driver has three bits that specify its behavior when an interrupt occurs. A functional diagram of the interrupt logic is shown below.
WDF Watchdog Timer WIE PF Power Monitor VINT AF Clock Alarm AIE PFE P/L Pin Driver H/L VCC
Power Fail Interrupt Enable - PFE. When set to 1, the power fail monitor drives the pin as well as an internal flag. When set to 0, the power fail monitor affects only the internal flag. High/Low - H/L. When set to a 1, the INT pin is active high and the driver mode is push-pull. The INT pin can drive high only when VCC>Vswitch. When set to a 0, the INT pin is active low and the drive mode is opendrain. Active low (open drain) is operational even in battery backup mode. Pulse/Level - P/L. When set to a 1 and an interrupt occurs, the INT pin is driven for approximately 200 ms. When P/L is set to a 0, the INT pin is driven high or low (determined by H/L) until the Flags/Control register is read. When an enabled interrupt source activates the INT pin, an external host can read the Flags/Control register to determine the cause. Remember that all flags will be cleared when the register is read. If the INT pin is programmed for Level mode, then the condition will clear and the INT pin will return to its inactive state. If the pin is programmed for Pulse mode, then reading the flag also will clear the flag and the pin. The pulse will not complete its specified duration if the Flags/Control register is read. If the INT pin is used as a host reset, then the Flags/Control register should not be read during a reset.
Figure 8. Interrupt Block Diagram
The three interrupts each have a source and an enable. Both the source and the enable must be active (true high) in order to generate an interrupt output. Only one source is necessary to drive the pin. The user can identify the source by reading the Flags/Control register, which contains the flags associated with each source. All flags are cleared to 0 when the register is read. The cycle must be a complete read cycle ( WE high); otherwise the flags will not be cleared. The power monitor has two programmable settings that are explained in the power monitor section. Once an interrupt source is active, the pin driver determines the behavior of the output. It has two programmable settings as shown below. Pin driver control bits are located in the Interrupts register.
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During a power-on reset with no battery, the interrupt register is automatically loaded with the value 24h. This causes power-fail interrupt to be enabled with an active-low pulse.
RTC Register Map
Register 0x7FFF 0x7FFE 0x7FFD 0x7FFC 0x7FFB 0x7FFA 0x7FF9 0x7FF8 0x7FF7 0x7FF6 0x7FF5 0x7FF4 0x7FF3 0x7FF2 0 0 0 0 0 OSCEN WDS WIE M M M M D7 D6 D5 10s Years 0 0 0 BCD Format Data D4 D3 10s Months D2 D1 Years Months Day of Month 0 Day of Week Hours Minutes Seconds Calibration WDT PFE ABE H/L P/L 0 0 D0 Function / Range Years: 00-99 Months: 01-12 Day of Month: 01-31 Day of week: 01-07 Hours: 00-23 Minutes: 00-59 Seconds: 00-59 Calibration values* Watchdog* Interrupts* Alarm, Day of Month: 01-31 Alarm, hours: 00-23 Alarm, minutes: 00-59 Alarm, seconds: 00-59 R Centuries: 00-99 Flags*
10s Day of Month 0 0 0 0 10s Hours 10s Minutes 10s Seconds Cal 0 Sign WDW AIE 0 0
10s Alarm Date 10s Alarm Hours
Alarm Day Alarm Hours Alarm Minutes Alarm Seconds 0 Centuries CAL W
10 Alarm Minutes 10 Alarm Seconds
0x7FF1 10s Centuries 0x7FF0 WDF AF PF OSCF * - Is a binary value, not a BCD value. 0 - Not implemented, reserved for future use.
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Register Map Detail
0x7FFF Timekeeping - Years D6 D5 D4 D3 D2 D1 D0 10s Years Years Contains the lower two BCD digits of the year. Lower nibble contains the value for years; upper nibble contains the value for 10s of years. Each nibble operates from 0 to 9. The range for the register is 0-99. D7 Timekeeping - Months D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 10s Month Months Contains the BCD digits of the month. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble (one bit) contains the upper digit and operates from 0 to 1. The range for the register is 1-12. Timekeeping - Date D7 D6 D5 D4 D3 D2 D1 D0 0 0 10s Day of month Day of month Contains the BCD digits for the date of the month. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper digit and operates from 0 to 3. The range for the register is 1-31. Leap years are automatically adjusted for. Timekeeping - Day D7 D6 D5 D4 D3 D2 D1 D0 0 0 0 0 0 Day of week Lower nibble contains a value that correlates to day of the week. Day of the week is a ring counter that counts from 1 to 7 then returns to 1. The user must assign meaning to the day value, as the day is not integrated with the date. Timekeeping - Hours D7 D6 D5 D4 D3 D2 D1 D0 12/24 0 10s Hours Hours Contains the BCD value of hours in 24 hour format. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble (two bits) contains the upper digit and operates from 0 to 2. The range for the register is 0-23. Timekeeping - Minutes D7 D6 D5 D4 D3 D2 D1 D0 0 10s Minutes Minutes Contains the BCD value of minutes. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper minutes digit and operates from 0 to 5. The range for the register is 0-59. Timekeeping - Seconds D7 D6 D5 D4 D3 D2 D1 D0 0 10s Seconds Seconds Contains the BCD value of seconds. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper digit and operates from 0 to 5. The range for the register is 059.
0x7FFE
0x7FFD
0x7FFC
0x7FFB
0x7FFA
0x7FF9
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0x7FF8 D7 D6 D5 Calibration / Control D4 D3 D2 D1 D0
OSCEN Calibration Sign Calibration
Calibration OSCEN 0 Calibration Sign Oscillator Enable. When set to 1, the oscillator is halted. When set to 0, the oscillator runs. Disabling the oscillator saves battery/capacitor power during storage. On a no-battery power-up, this bit is set to 0. Determines if the calibration adjustment is applied as an addition to or as a subtraction from the time-base. These five bits control the calibration of the clock.
0x7FF7
D7 WDS
D6 WDW
D5
Watchdog Timer D4 D3
D2 WDT
D1
D0
WDS
WDW
WDT
Watchdog Strobe. Setting this bit to 1 reloads and restarts the watchdog timer. Setting the bit to 0 has no affect. The bit is cleared automatically once the watchdog timer is reset. The WDS bit is write only. Reading it always will return a 0. Watchdog Write Enable. Setting this bit to 1 masks the watchdog time-out value (WDT5-WDT0) so it cannot be written. This allows the user to strobe the watchdog without disturbing the time-out value. Setting this bit to 0 allows bits 5-0 to be written on the next write to the Watchdog register. The new value will be loaded on the next internal watchdog clock after the write cycle is complete. This function is explained in more detail in the watchdog timer section. Watchdog time-out selection. The watchdog timer interval is selected by the 6-bit value in this register. It represents a multiplier of the 32 Hz count (31.25 ms). The minimum range or time-out value is 31.25 ms (a setting of 1) and the maximum time-out is 2 seconds (setting of 3Fh). Setting the watchdog timer register to 0 disables the timer. These bits can be written only if the WDW bit was cleared to 0 on a previous cycle.
0x7FF6
D7 WIE
D6 AIE
D5 PFIE
Interrupt Status / Control D4 D3 D2 ABE H/L P/L
D1 0
D0 0
WIE AIE PFIE ABE H/L P/L
Watchdog Interrupt Enable. When set to 1 and a watchdog time-out occurs, the watchdog timer drives the INT pin as well as the WDF flag. When set to 0, the watchdog time-out affects only the WDF flag. Alarm Interrupt Enable. When set to 1, the alarm match drives the INT pin as well as the AF flag. When set to 0, the alarm match only affects the AF flag. Power-Fail Enable. When set to 1, the alarm match drives the INT pin as well as the AF flag. When set to 0, the power-fail monitor affects only the PF flag. Alarm Battery-backup Enable. When set to 1, the alarm interrupt (as controlled by AIE) will function even in battery backup mode. When set to 0, the alarm will occur only when Vcc>Vswitch. High/Low. When set to a 1, the INT pin is driven active high. When set to 0, the INT pin is open drain, active low. Pulse/Level. When set to a 1, the INT pin is driven active (determined by H/L ) by an interrupt source for approximately 200 ms. When set to a 0, the INT pin is driven to an active level (as set by H/L ) until the Flags/Control register is read.
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0x7FF5 D7 M D6 0 D5 D4 Alarm - Day D3 D2 D1 Alarm Date D0
10s Alarm Date
M
Contains the alarm value for the date of the month and the mask bit to select or deselect the date value. Match. Setting this bit to 0 causes the date value to be used in the alarm match. Setting this bit to 1 causes the match circuit to ignore the date value. Alarm - Hours D3
0x7FF4
D7 M
D6 0
D5
D4
D2
D1 Alarm Hours
D0
10s Alarm Hours
M
Contains the alarm value for the hours and the mask bit to select or deselect the hours value. Match. Setting this bit to 0 causes the hours value to be used in the alarm match. Setting this bit to 1 causes the match circuit to ignore the hours value. Alarm - Minutes D4 D3
0x7FF3
D7 M
D6
D5 10s Alarm Minutes
D2
D1 Alarm Minutes
D0
M
Contains the alarm value for the minutes and the mask bit to select or deselect the minutes value. Match. Setting this bit to 0 causes the minutes value to be used in the alarm match. Setting this bit to 1 causes the match circuit to ignore the minutes value.
0x7FF2
D7 M
D6
D5 10s Alarm Seconds
Alarm - Seconds D4 D3
D2
D1 Alarm Seconds
D0
M
Contains the alarm value for the seconds and the mask bit to select or deselect the seconds' value. Match. Setting this bit to 0 causes the seconds' value to be used in the alarm match. Setting this bit to 1 causes the match circuit to ignore the seconds value.
0x7FF1
D7 0
D6 0
Timekeeping - Centuries D5 D4 D3 D2 10s Centuries
D1 Centuries
D0
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0x7FF0 Flags D7 D6 D5 D4 D3 D2 D1 D0 WDF AF PF OSCF 0 CAL W R Watchdog Timer Flag. This read-only bit is set to 1 when the watchdog timer is allowed to reach 0 without being reset by the user. It is cleared to 0 when the Flags/Control register is read. Alarm Flag. This read-only bit is set to 1 when the time and date match the values stored in the alarm registers with the match bits = 0. It is cleared when the Flags/Control register is read. Power-fail Flag. This read-only bit is set to 1 when power falls below the power-fail threshold Vswitch. It is cleared to 0 when the Flags/Control register is read. Oscillator Fail Flag. Set to 1 on power-up only if the oscillator is not running in the first 5ms of power-on operation. This indicates that time counts are no longer valid. The user must reset this bit to 0 to clear this condition. The chip will not clear this flag. This bit survives power cycles. Calibration Mode. When set to 1, a 512Hz square wave is output on the INT pin. When set to 0, the INT pin resumes normal operation. This bit defaults to 0 (disabled) on power up. Write Time. Setting the W bit to 1 freeze updates of the timekeeping registers. The user can then write them with updated values. Setting the W bit to 0 causes the contents of the time registers to be transferred to the timekeeping counters. Read Time. Setting the R bit to 1 copies a static image of the timekeeping registers and places them in a holding register. The user can then read them without concerns over changing values causing system errors. The R bit going from 0 to 1 causes the timekeeping capture, so the bit must be returned to 0 prior to reading again.
WDF AF PF OSCF CAL W
R
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ORDERING INFORMATION
STK17T88 - R F 45 I
Temperature Range
Blank = Commercial (0 to 70 C) I = Industrial (-40 to 85C)
Access Time
25 = 25ns 35 = 35ns 45 = 45ns
Lead Finish
Blank = 85% Sn / 15% Pb F = 100% Sn (Matte Tin) ROHS Compliant
Package
R = Plastic 48-pin 300 mil SSOP (25 mil pitch) W = Plastic 40-pin 600 mil DIP (100 mil pitch)
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Document Revision History
Revision 0.0 0.1 Date February 2003 March 2003 Summary Publish new datasheet Remove 525 mil SOIC, Add 48 Pin SSOP and 40 Pin DIP packages; Modified Block Diagram in AutoStore description section
Parameter
Vcap Min tVCCRISE ICC1 Max Com. ICC1 Max Com. ICC1 Max Com. ICC1 Max Ind. ICC1 Max Ind. ICC1 Max Ind. ICC2 Max ICC4 Max tHRECALL tSTORE tRECALL tGLQV
Old Value
10F NA 35 mA 40 mA 50 mA 35 mA 45 mA 55 mA 1.5 mA 0.5 mA 5 ms 10 ms 20 s 10 ns
New Value
17 F 150 s 50 mA 55 mA 65 mA 55 mA 60 mA 70 mA 3.0 mA 3 mA 20 ms 12.5 ms 40 s 12 ns
Notes
New Spec @ 45ns access @ 35ns access @ 25ns access @ 45ns access @ 35ns access @ 25ns access Com. & Ind. Com & Ind.
1.0
December 2004
@ 25ns access
1.1 1.2
January 2005 April 2005
Changed "N" package reference to "R" package. Changed RTC register unused bits "X" to require zero "0" value when writing values.
SIMTEK STK17T88 Data Sheet, April 2005 Copyright 2005, Simtek Corporation. All rights reserved. This datasheet may only be printed for the express use of Simtek Customers. No part of this datasheet may be reproduced in any other form or means without express written permission from Simtek Corporation. The information contained in this publication is believed to be accurate, but changes may be made without notice. Simtek does not assume responsibility for, or grant or imply any warranty, including MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE regarding this information, the product or its use. Nothing herein constitutes a license, grant or transfer of any rights to any Simtek patent, copyright, trademark or other proprietary right.
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