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STK17TA8
nvTimeTM Event Data Recorder
128K x 8 AutoStoreTM nvSRAM with Real-Time Clock
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FEATURES
* Data Integrity of Simtek nvSRAM Combined with Full-Featured Real-Time Clock * 25ns, 35ns and 45ns Access Times * Software or AutoStoreTMSTORE to QuantumTrapTM Nonvolatile Elements * RECALL to SRAM Initiated by Software or Power Restore * Unlimited READ, WRITE and RECALL Cycles * 100-Year Data Retention * Watchdog Timer * Clock Alarm with programmable Interrupts * Capacitor or battery backup for RTC * Single 3V +20%, -10% Operation * Commercial and Industrial Temperatures * Packages: 48 pin SSOP, 40 pin DIP
DESCRIPTION
The Simtek STK17TA8 combines a 1 Mbit 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
HSB Quantum Trap 1024 x 1024
ROW DECODER
VCCX
VCAP Vrtcbat Vrtccap
A5 A6 A7 A8 A9 A12 A13 A14 A15 A16
DQ0 DQ1 DQ2 DQ3 DQ4 DQ5 DQ6 DQ7
STORE STATIC RAM ARRAY 1024 x 1024 RECALL
STORE/ RECALL CONTROL
POWER CONTROL SOFTWARE DETECT
A0 - A16
INPUT BUFFERS
COLUMN I/O COLUMN DEC
RTC
X1 X2 INT
A0 A1 A2 A3 A4 A10 A11
MUX
A0 A16 G E W
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PACKAGES
48 Pin 300 mil SSOP
(not to scale)
40 Pin 600 mil DIP
PIN DESCRIPTIONS
Pin Name A0 - A16 DQ0 -DQ7 E W G X1, X2 Vrtccap Vrtcbat VCCX HSB INT I/O Input I/O Input Input Input Input Power Supply Power Supply Power Supply I/O Output Description Address: The 17 address inputs select one of 131,072 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 clock. Chip Enable: The active low E input selects the device. Write Enable: The active low W enables data on the DQ pins to be written to the adddress location latched by the falling edge of E. Output Enable: The active low G input enables the data output buffers during read cycles. Deasserting G high causes the DQ pins to tri-state. Crystal: Connections for 32.768 kHz crystal. Capacitor supplied backup RTC supply voltage. Battery supplied backup RTC supply voltage. Power (+ 3V) Hardware Store Busy (I/O) 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
VCAP VSS
Power Supply Power Supply
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ABSOLUTE MAXIMUM RATINGSa
Power Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . .-0.5V to +3.9V Voltage on Input Relative to VSS . . . . . . . . . . -0.5V to (VCC + 0.5V) Voltage on DQ0-7 . . . . . . . . . . . . . . . . . . . . . . -0.5V to (VCC + 0.5V) Temperature under Bias . . . . . . . . . . . . . . . . . . . . . -55C to 125C Storage Temperature. . . . . . . . . . . . . . . . . . . . . . . . -65C to 150C Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W DC Output Current (1 output at a time, 1s duration) . . . . . . . . 15mA
Note 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.
DC CHARACTERISTICS(VCC = 3.0V +20%, -10%)e
SYMBOL ICC
b
PARAMETER Average VCC Current
COMMERCIAL MIN MAX 70 60 55 1 5 0.5 0.3 1 1 200 1.6 2.0 VSS - .5 2.4 0.4 0 70 VCC + .3 0.8
INDUSTRIAL MIN MAX 75 65 60 1 5 0.5 0.3 1 1 300 1.6 2.0 VSS - .5 2.4 0.4 - 40 85 VCC + .3 0.8
UNITS mA mA mA mA mA mA mA A A nA V V V V V C All Inputs All Inputs IOUT = - 2mA IOUT = 4mA tAVAV = 25ns tAVAV = 35ns tAVAV = 45ns
NOTES
1
ICC ICC ICC
c b
2 3 c
Average VCC Current during STORE Average VCC Current at tAVAV = 200ns 3V, 25C, Typical Average VCAP Current during AutoStoreTM Cycle VCC Standby Current (Standby, Stable CMOS Input Levels) Input Leakage Current Off-State Output Leakage Current RTC Backup Current RTC Backup Voltage Input Logic "1" Voltage Input Logic "0" Voltage Output Logic "1" Voltage Output Logic "0" Voltage Operating Temperature
All Inputs Don't Care, VCC = max W (V CC - 0.2V) All Others Cycling, CMOS Levels All Inputs Don't Care E (V CC - 0.2V) All Others VIN 0.2V or (VCC - 0.2V) VCC = max VIN = VSS to VCC VCC = max VIN = VSS to VCC, E or G VIH
4
ISBd IILK IOLK IBAK VBAK VIH VIL VOH VOL TA
Note b: Note c: Note d: Note e:
ICC and ICC are dependent on output loading and cycle rate. The specified values are obtained with outputs unloaded. 1 3 ICC and ICC are the average currents required for the duration of the respective STORE cycles (tSTORE ) . 2 4 E VIH will not produce standby current levels until any nonvolatile cycle in progress has timed out. VCC reference levels throughout this datasheet refer to VCCX. 3.0V
AC TEST CONDITIONS
Input Pulse Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0V to 3V Input Rise and Fall Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5ns Input and Output Timing Reference Levels . . . . . . . . . . . . . . . 1.5V Output Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Figure 1
577 Ohms OUTPUT 789 Ohms 30 pF INCLUDING SCOPE AND FIXTURE
CAPACITANCEf
SYMBOL CIN COUT PARAMETER Input Capacitance Output Capacitance
(TA = 25C, f = 1.0MHz)
MAX 5 7 UNITS pF pF CONDITIONS V = 0 to 3V V = 0 to 3V
Figure 1: AC Output Loading
Note f:
These parameters are guaranteed but not tested.
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SRAM READ CYCLES #1 & #2
NO. 1 2 3 4 5 6 7 8 9 10 11 SYMBOLS #1, #2 tELQV tAVAVg tAVQVh tGLQV tAXQXh tELQX tEHQZi tGLQX tGHQZi tELICCHf tEHICCLf Alt. tACS tRC tAA tOE tOH tLZ tHZ tOLZ tOHZ tPA tPS PARAMETER 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 0 35 3 3 10 0 13 0 45 25 25 10 3 3 13 0 15 MIN
(VCC = 3.0V +20%, -10%)e
STK17TA8-25 MAX 25 35 35 15 3 3 15 STK17TA8-35 MIN MAX 35 45 45 20 STK17TA8-45 MIN MAX 45 UNITS ns ns ns ns ns ns ns ns ns ns ns
Note g: W must be high during SRAM READ cycles. Note h: Device is continuously selected with E and G both low. Note i: Measured 200mV from steady state output voltage.
SRAM READ CYCLE #1: Address Controlledg, h
2 tAVAV ADDRESS 5 tAXQX DQ (DATA OUT) 3 tAVQV
DATA VALID
SRAM READ CYCLE #2: E Controlledg
2 tAVAV ADDRESS 6 1 tELQV 1 1 tEHICCL 7 tEHQZ
E
tELQX
G 8 4 tGLQV
9 tGHQZ
tGLQX DQ (DATA OUT)
DATA VALID
tELICCH
ACTIVE
10
ICC
STANDBY
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SRAM WRITE CYCLES #1 & #2
NO. 12 13 14 15 16 17 18 19 20 21 SYMBOLS #1 tAVAV tWLWH tELWH tDVWH tWHDX tAVWH tAVWL tWHAX t WLQZ i, j tWHQX #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 3 PARAMETER MIN 25 20 20 10 0 20 0 0 10 3
(VCC = 3.0V +20%, -10%)e
STK17TA8-25 MAX STK17TA8-35 MIN 35 25 25 12 0 25 0 0 13 3 MAX STK17TA8-45 MIN 45 30 30 15 0 30 0 0 15 MAX UNITS ns ns ns ns ns ns ns ns ns ns
Note j: If W is low when E goes low, the outputs remain in the high-impedance state. Note k: E or W must be VIH during address transitions. Note l: HSB must be high during SRAM write cycles.
SRAM WRITE CYCLE #1: W Controlledk, l
12 tAVAV ADDRESS 14 tELWH E 17 tAVWH 13 tWLWH 15 tDVWH DATA IN tWLQZ DATA OUT
PREVIOUS DATA HIGH IMPEDANCE DATA VALID
19 tWHAX
tAVWL W
18
16 tWHDX
20
21 tWHQX
SRAM WRITE CYCLE #2: E Controlledk, l
12 tAVAV ADDRESS 18 tAVEL E 14 tELEH 19 tEHAX
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 A15 - A0 (hex) X X X 4E38 B1C7 83E0 7C1F 703F 8B45 4E38 B1C7 83E0 7C1F 703F 4B46 4E38 B1C7 83E0 7C1F 703F 8FC0 4E38 B1C7 83E0 7C1F 703F 4C63 MODE Not Selected Read SRAM Write SRAM Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Autostore Inhibit Read SRAM Read SRAM Read SRAM Read SRAM Read SRAM Autostore inhibit off 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
m, n, o
L
H
L
Active
m, n, o
L
H
L
Active
m, n, o
lCC
2
L
H
L
Active
m, n, o
Note m: The six consecutive addresses must be in the order listed. W must be high during all six consecutive cycles to enable a nonvolatile cycle. Note n: While there are 17 addresses on the STK17TA8, only the lower 16 are used to control software modes. Note o: 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
NO. 22 23 24 SYMBOLS Standard tRESTORE tSTORE VSWITCH tHLHZ Alternate PARAMETER Power-up RECALL Duration STORE Cycle Duration Low Voltage Trigger Level 2.55
(VCC = 3.0V +20%, -10%)e
STK17TA8 MIN MAX 5 10 2.65 UNITS ms ms V NOTES p q
Note p: tRESTORE starts from the time VCC rises above VSWITCH. Note q: 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
AutoStoreTM 23 tSTORE POWER-UP RECALL 22 tRESTORE W
DQ (DATA OUT)
POWER-UP RECALL
BROWN OUT NO STORE (NO SRAM WRITES)
BROWN OUT AutoStoreTM
BROWN OUT AutoStoreTM RECALL WHEN VCC RETURNS ABOVE VSWITCH
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SOFTWARE-CONTROLLED STORE/RECALL CYCLEs
NO. 25 26 27 28 29 SYMBOLS E cont tAVAV tAVEL tELEH tELAX tRECALL G cont tAVAV tAVGL tGLGH tGLAX tRECALL Alternate tRC tAS tCW PARAMETER STORE/RECALL Initiation Cycle Time Address Set-up Time Clock Pulse Width Address Hold Time RECALL Duration STK17TA8-25 MIN 25 0 20 20 20 MAX
(VCC = 3.0V +20%, -10%)e
STK17TA8-35 MIN 35 0 25 20 20 MAX STK17TA8-45 MIN 45 0 30 20 20 MAX UNITS NOTES ns ns ns ns s s
Note r: The software sequence is clocked with E controlled READs or G controlled READs. Note s: The six consecutive addresses must be in the order listed in the Hardware Mode Selection Table: (4E38, B1C7, 83E0, 7C1F, 703F, 8FC0) for a STORE cycle or (4E38, B1C7, 83E0, 7C1F, 703F, 4C63) for a RECALL cycle. W must be high during all six consecutive cycles.
SOFTWARE STORE/RECALL CYCLE: E CONTROLLEDs
tAVAV ADDRESS
26 ADDRESS #1 25
tAVAV
ADDRESS #6
25
tAVEL E
tELEH
27
tELAX G
23 29 / tRECALL
28
tSTORE DQ (DATA)
DATA VALID DATA VALID
HIGH IMPEDANCE
SOFTWARE STORE/RECALL CYCLE: G CONTROLLEDs
tAVAV ADDRESS
ADDRESS #1 25
tAVAV
ADDRESS #6
25
E
tAVGL G
26
tGLGH
27
tGLAX DQ (DATA)
DATA VALID DATA VALID
28
tSTORE
23
29 / tRECALL
HIGH IMPEDANCE
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HARDWARE STORE CYCLEt (VCC = 3.0V +20%, -10%)e
NO. 30 31 32 33 34 SYMBOLS Standard tSTORE tDELAY tRECOVER tHLHX tHLBL Alternate tHLHZ tHLQZ tHHQX STORE Cycle Duration Time Allowed to Complete SRAM Cycle Hardware STORE High to Inhibit Off Hardware STORE Pulse Width Hardware STORE Low to STORE Busy 15 300 1 100 PARAMETER STK17TA8 MIN MAX 10 UNITS ms s ns ns ns NOTES i i t
Note t:
tRECOVER is only applicable after tSTORE is complete.
HARDWARE STORE CYCLE
33 tHLHX HSB (IN) 32 tRECOVER 30 tSTORE
HSB (OUT)
34 tHLBL
HIGH IMPEDANCE HIGH IMPEDANCE
tDELAY DQ (DATA OUT)
DATA VALID DATA VALID
31
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DEVICE OPERATION
nvSRAM
The STK17TA8 has two separate modes of operation: SRAM mode and nonvolatile mode. In SRAM mode, the memory operates as a standard fast static RAM. In nonvolatile mode, data is transferred from SRAM to the nonvolatile elements (the STORE operation) or from the nonvolatile elements to SRAM (the RECALL operation). In this mode SRAM functions are disabled. The STK17TA8 supports unlimited reads and writes to the SRAM, unlimited recalls from the nonvolatile elements and up to 1 million stores to the nonvolatile elements current from VCCX to charge a capacitor connected to the VCAP pin. This stored charge will be used by the chip to perform a single STORE operation. After power up, when the voltage on the VCCX pin drops below VSWITCH, the part will automatically disconnect the VCAP pin from VCCX and initiate a STORE operation. Figure 2 shows the proper connection of capacitors for automatic store operation. A charge storage capacitor having a capacity of between 10F and 100F ( 20%) rated at minimum of 5V should be provided. In order to prevent unneeded STORE operations, automatic STOREs as well as those initiated by externally driving HSB low, 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. HSB can be used to signal the system that the AutoStoreTM cycle is in progress.
10k
SRAM READ
The STK17TA8 performs a READ cycle whenever E and G are low and W is high. The address specified on pins A0-16 determines which of the 131,072 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 is brought low.
Vcap
Vccx
10F 5v, 20%
+
W
A WRITE cycle is performed whenever E and W are low. 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.
Vss
Figure 2: AutoStoreTM Mode
If HSB is not used it should be left unconnected
HSB OPERATION
The STK17TA8 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 STK17TA8 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
AutoStoreTM OPERATION
The STK17TA8 can be powered in one of three modes. During normal operation, the STK17TA8 will draw
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0.1F Bypass
SRAM WRITE
10k
STK17TA8
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
SOFTWARE NONVOLATILE STORE
The STK17TA8 software STORE cycle is initiated by executing sequential E controlled READ cycles from six specific address locations. During the STORE cycle an erase of the previous nonvolatile data is first performed, followed by a program of the nonvolatile elements. The program operation copies the SRAM data into nonvolatile memory. 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 4E38 (hex) B1C7 (hex) 83E0 (hex) 7C1F (hex) 703F (hex) 8FC0 (hex) Valid READ Valid READ Valid READ Valid READ Valid READ Initiate STORE cycle
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 STK17TA8 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. The HSB pin can be used to synchronize one STK17TA8 with one or more STK14CA8 nvSRAMs to expand the memory space. To operate in this mode the HSB pins from each device should be connected together. An external pull-up resistor to + 3.0V is required since HSB acts as an open drain pull down. The VCAP pins from the other parts can be tied together and share a single capacitor. The capacitor size must be scaled by the number of devices connected to it. When any one of the devices detects a power loss and asserts HSB, the common HSB pin will cause all parts to request a STORE cycle (a STORE will take place in those devices that have been written since the last nonvolatile cycle). During any STORE operation, regardless of how it was initiated, the STK17TA8 will continue to drive the HSB pin low, releasing it only when the STORE is complete. Upon completion of the STORE operation the STK17TA8 will remain disabled until the HSB pin returns high. If HSB is not used, it should be left unconnected.
The software sequence may be clocked with E controlled READs or G controlled READs. 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 NONVOLATILE RECALL
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 4E38 (hex) B1C7 (hex) 83E0 (hex) 7C1F (hex) 703F (hex) 4C63 (hex) Valid READ Valid READ Valid READ Valid READ Valid READ Initiate RECALL cycle
POWER-UP RECALL
During power up, or after any low-power condition (VCCX < VSWITCH), an internal RECALL request will be latched. When VCAP once again exceeds the sense voltage of VSWITCH, a RECALL cycle will automatically be initiated and will take tRESTORE to complete. If the STK17TA8 is in a WRITE state at the end of power-up RECALL, the WRITE will be inhibited and E or W must be brought high and then low for a write to initiate.
Internally, RECALL is a two-step procedure. First, the SRAM data is cleared, and second, the nonvolatile
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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.
WRITEs will be inhibited.
LOW AVERAGE ACTIVE POWER The STK17TA8 draws significantly less current when it is cycled at times longer than 50ns. Figure 3 shows the relationship between ICC and READ cycle time. Worst-case current consumption is shown for commercial temperature range, VCC = 3.6V, and 100% duty cycle on chip enable. Figure 4 shows the same relationship for WRITE cycles. If the chip enable duty cycle is less than 100%, only standby current is drawn when the chip is disabled. The overall average current drawn by the STK17TA8 depends on the following items: 1) the duty cycle of chip enable; 2) the overall cycle rate for accesses; 3) the ratio of READs to WRITEs; 4) the operating temperature; 5) the Vcc level; and 6) I/O loading.
50
PREVENTING STORES
The AutoStoreTM function can be disabled by initiating an AutoStore Inhibit sequence. A sequence of read operations is performed in a manner similar to the software STORE initiation. To initiate the AutoStore Inihibit 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 4E38 (hex) B1C7 (hex) 83E0 (hex) 7C1F (hex) 703F (hex) 8B45 (hex) Valid READ Valid READ Valid READ Valid READ Valid READ AutoStore Inhibit
Average Active Current (mA)
The AutoStore Inhibit can be disabled by initiating an AutoStore Inhibit Off sequence. A sequence of read operations is performed in a manner similar to the software RECALL initiation. To initiate the AutoStore Inhibit Off 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 4E38 (hex) B1C7 (hex) 83E0 (hex) 7C1F (hex) 703F (hex) 4B46 (hex) Valid READ Valid READ Valid READ Valid READ Valid READ AutoStore Inhibit Off
40
30
20
10
0 50 100 150 Cycle Time (ns) 200
The last AutoStore Inhibit state is stored in nonvolatile memory and is retained through power cycling.
Figure 3: Icc (max) Reads
50
NOISE CONSIDERATIONS
Average Active Current (mA)
The STK17TA8 is a high-speed memory and so must have a high-frequency bypass capacitor of approximately 0.1F connected between VCAP and VSS, using leads and traces that are as short as possible. As with all high-speed CMOS ICs, normal careful routing of power, ground and signals will help prevent noise problems.
40
30
20
HARDWARE WRITE PROTECT
The STK17TA8 offers hardware protection against inadvertent STORE operation and SRAM WRITEs during low-voltage conditions. When VCCX < VSWITCH, all externally initiated STORE operations and SRAM
10
0 50 100 150 Cycle Time (ns) 200
Figure 4: Icc (max) Writes
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nvTIME OPERATION
The STK17TA8 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.
BACKUP POWER
The STK17TA8 is intended for permanently powered operation, but when primary power, Vcc, fails and drops below Vswitch the device will switch to backup power from either Vbakcap or Vbakbat, depending on whether a capacitor or battery is chosen for the application. 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 vSRAM 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 tradeoff of using a battery versus a capacitor. During backup operation the STK17TA8 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
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.
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 STK17TA8 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 (in the control register 1FFF0h), 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 10 msec after a "0" is written to the read bit, all STK17TA8 registers are simultaneously updated.
Using a capacitor has the obvious advantage of recharging the backup source each time the system is powered up. If a battery is used a 3V lithium is recommended and the STK17TA8 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 STK17TA8. The battery capacity should be chosen for total anticipated cumulative down-time required over the life of the system.
SETTING THE CLOCK
Setting the write bit (in the control register 1FFF0h) to a "1" halts updates to the STK17TA8 registers. The correct day, date and time can then be written into the registers in 24-hour BCD format. Resetting the write bit to "0" transfers those values to the actual clock counters, after which the clock resumes normal operation.
STOPPING AND STARTING THE OSCILLATOR
The oscillator may be stopped at any time. This feature may be used to save battery or capacitor energy during long-term storage to increase shelf life. Setting the OSCEN bit in register 1FFF8h to 1 halts the oscillator. Setting the bit to 0 enables the oscillator. The RTC does not run until the oscillator
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is enabled. ues 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 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 register 1FFF0h 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.
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 STK17TA8 employs a calibration circuit that can improve the accuracy to + 1/-2 ppm at 25C. The 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 control register 1FFF8h. Adding counts speeds the clock up; subtracting counts slows the clock down. The Calibration bits occupy the 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 register 1FFF0h 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.
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 timeout value in register 1FFF7h is loaded into the
ALARM
The alarm function compares user-programmed val-
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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 timeout interrupt by setting WDS bit to 1 prior to the counter reaching 0. This causes the counter to be reloaded with the watchdog timeout 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 timeout 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 timeout 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 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 timeout value to 0 would be otherwise meaningless and therefore disables the watchdog function. The output of the watchdog timer is a flag bit WDF that is set if the watchdog is allowed to timeout. The flag is set upon a watchdog timeout 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 timeout occurs. 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 descibed 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 Vccx 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 the user 10 msec after Vcc has been restored to the device.
INTERRUPTS
The STK17TA8 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.
POWER MONITOR
The STK17TA8 provides a power management
Figure 6. Interrupt Block Diagram Figure 5. Watchdog Timer 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
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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. 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 (opendrain) 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 oneshot 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 timeout occurs. WhenWIE 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 fla. When set to 0, the alarm match only affects to internal flag. 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. Alarm Battery-backup Enable - ABE. When set to 1, the clock 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. AIE should only be set when the INT pin is programmed for active low operation. In addition, it only functions with the clock alarm, not the watchdog. If enabled, the power monitor will drive the interrupt during all normal Vcc conditions regardless of the ABE bit. The application for ABE is intended for power control, where the system powers up at a predetermined time. Depending on the application, it may require dedicating the INT pin to this function. 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 open-drain. 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, as 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 cannot be read during a reset. 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.
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RTC Register Map
Register D7 1FFFFh 1FFFEh 1FFFDh 1FFFCh 1FFFBh 1FFFAh 1FFF9h 1FFF8h 1FFF7h 1FFF6h 1FFF5h 1FFF4h 1FFF3h 1FFF2h 1FFF1h 1FFF0h X - resevered for future use * - not BCD values WDF X X X X X X OSCEN WDS WIE M M M M X WDW AIE X X PFE ABE H/L X X X X D6 10 Years X 10s Months D5 BCD DATA D4 D3 D2 Years Months Day of Month X Day of Week Hours Minutes Seconds Calibration WDT P/L alarm date alarm hours alarm minutes alarm seconds Centuries X X CAL W R X X D1 D0 FUNCTION/RANGE Years: Months: 00 - 99 01 - 12
10s Day of month X X 10s Hours 10s Minutes 10s Seconds Cal Sign
Day of Month:01 - 31 Day of Week:01 - 07 Hours: Minutes: 00 - 23 00 - 59
Seconds: 00 - 59 Calibration values* Watchdog* Interrupts* Alarm, Day of the Month: 01-31 Alarm, Hours: 00-23 Alarm, minutes: 00-59 Alarm, seconds: 00-59 Centuries: 00 - 99 Flags*
10s alarm date 10s alarm hours 10 alarm minutes 10 alarm seconds
10s Centuries AF PF
Register Map Detail
1FFFFh Timekeeping - Years D7 D6 10 Years D5 D4 D3 D2 Years D1 D0
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.
1FFFEh
Timekeeping - Months D7 X D6 X D5 X D4 10s Months D3 D2 Months D1 D0
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.
1FFFDh
Timekeeping - Date D7 X D6 X D5 D4 D3 D2 Day of Month D1 D0
10s 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.
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1FFFCh
Timekeeping - Day D7 X D6 X D5 X D4 X D3 X D2 Day of Week D1 D0
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 meanting to the day value, as the day is not integrated with the date.
1FFFBh
Timekeeping - Hours D7 12/24 D6 X D5 10s Hours D4 D3 D2 Hours D1 D0
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.
1FFFAh
Timekeeping - Minutes D7 X D6 D5 10s Minutes D4 D3 D2 Minutes D1 D0
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.
1FFF9h
Timekeeping - Seconds D7 X D6 D5 10s Seconds D4 D3 D2 Seconds D1 D0
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 0-59.
1FFF8h
Contol/Calibration D7 OSCEN D6 X D5 Calibration Sign D4 D3 D2 Calibration D1 D0
OSCEN Calibration Sign Calibration
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 1. The RTC will not run until the oscillator is enabled. Set this bit to 0 to activate the RTC. 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.
1FFF7h
Watchdog Timer D7 WDS D6 WDW D5 D4 D3 WDT D2 D1 D0
WDS
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 timeout value (WDT5-WDT0) so it cannot be written. This allows the user to strobe the watchdg without disturbing the timeout value. Setting this bit to 0 allows bits 5-0 to be witten on the next write to the Watchdog register. The new value will be loaded on the nex internal watchdog clock after the write cycle is complete. This function is explained in more detail in the watchdog timer section.
WDW
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1FFF7h Watchdog Timer D7 D6 D5 D4 D3 D2 D1 D0 Watchdog timeout 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 timeout value is 31.25 ms (a setting of 1) and the maximum timeout 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.
WDT
1FFF6h
Interrupt Status/Control D7 WIE D6 AIE D5 PFE D4 ABE D3 H/L D2 P/L D1 X D0 X
WIE AIE PFE ABE H/L P/L
Watchdog Interrupt Enable. When set to 1 and a watchdog timeout occurs, the watchdog timer drives the INT pin as well as the WDF flag. When set to 0, the watchdog timeout affects only the WDF flag. Alarm Interrup 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. Alarm - Day D7 M D6 0 D5 D4 10s alarm date D3 D2 alarm date D1 D0
1FFF5h
Contains the alarm value for the date of the month and the mask bit to select or deselect the date value. M 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.
1FFF4h
Alarm - Hours D7 M D6 0 D5 D4 10s alarm hours D3 D2 D1 alarm hours D0
Contains the alarm value for the hours and the mask bit to select or deselect the hours value. M 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.
1FFF3h
Alarm - Minutes D7 M D6 D5 10s alarm minutes D4 D3 D2 D1 alarm minutes D0
Contains the alarm value for the minutes and the mask bit to select or deselect the minutes value M 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.
1FFF2h
Alarm - Seconds D7 M D6 D5 10s alarm seconds D4 D3 D2 D1 alarm seconds D0
Contains the alarm value for the seconds and the mask bit to select or deselect the seconds value
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1FFF2h M Alarm - Seconds D7 D6 D5 D4 D3 D2 D1 D0 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.
1FFF1h
Timekeeping - Centuries D7 X D6 X D5 10s Centuries D4 D3 D2 Centuries D1 D0
1FFF0h
Flags D7 WDF D6 AF D5 PF D4 X D3 X D2 CAL D1 W D0 R
WDF AF PF CAL W
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. Calibration Mode. When set to 1, the clock enters calibration mode. When set to 0, the clock operates normally. Write Time. Setting the W bit to 1 freezes 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.
R
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STK17TA8 ORDERING INFORMATION
STK17TA8 - R F 45 I
Temperature Range
Blank = Commercial (0 to 70C) 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)
Package
R = Plastic 48-pin 300 mil SSOP W = Plastic 40-pin 600 mil DIP
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Document Revision History
Revision 0.0 0.1
Date February 2003 March 2003 June 2003 February 2004
Summary Publish new datasheet Remove 525 mil SOIC, Add 48 Pin SSOP and 40 Pin DIP packages; Modified Block Diagram in AutoStore description section Modify 600 mil DIP pinout (switch pins 32 and 33), Update Power-up Recall specs, Update Software Controlled Store/Recall Cycle, Added Hardware Store Description, Modified Mode Selection Table, Updated Vswitch, Updated tstore, Modify IBAK and VBAK Change part number from STK17CA8 to STK17TA8; Add lead-free finish option
0.2 0.3
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