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STK16C68-WF25 Datasheet(PDF) 7 Page - Simtek Corporation |
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STK16C68-WF25 Datasheet(HTML) 7 Page - Simtek Corporation |
7 / 10 page STK16C68 March 2006 7 Document Control # ML0010 rev 0.2 The AutoStorePlus™ STK16C68 is a fast 8K x 8 SRAM that does not lose its data on power-down. The data is preserved in integral QuantumTrap™ Nonvolatile Elements while power is unavailable. The nonvolatility of the STK16C68 does not require any system intervention or support: AutoStore- Plus™ on power-down and automatic RECALL on power-up guarantee data integrity without the use of batteries. NOISE CONSIDERATIONS Note that the STK16C68 is a high-speed memory and so must have a high-frequency bypass capaci- tor of approximately 0.1 μF connected between V CC and V SS, 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. SRAM READ The STK16C68 performs a READ cycle whenever E and G are low and W is high. The address specified on pins A 0-12 determines which of the 8,192 data bytes will be accessed. When the READ is initiated by an address transition, the outputs will be valid after a delay of t AVQV (READ cycle #1). If the READ is initiated by E or G, the outputs will be valid at t ELQV or at t GLQV, whichever is later (READ cycle #2). The data outputs will repeatedly respond to address changes within the t AVQV access time without the need for tran- sitions 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. SRAM WRITE 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 DQ 0-7 will be writ- ten into the memory if it is valid t DVWH before the end of a W controlled WRITE or t DVEH 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 the common I/O lines. If G is left low, internal circuitry will turn off the output buffers t WLQZ after W goes low. AutoStorePlus™ OPERATION The STK16C68’s automatic STORE on power-down is completely transparent to the system. The AutoStore™ initiation takes less than 500ns when power is lost (V CC < VSWITCH) at which point the part depends only on its internal capacitor for STORE completion. This safe transfer of data from SRAM to Nonvolatile Elements takes place regardless of power supply slew rate. In order to prevent unneeded STORE operations, the automatic STORE 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 or not a WRITE operation has taken place. POWER-UP RECALL During power up, or after any low-power condition (V CC < VRESET), an internal RECALL request will be latched. When V CC once again exceeds the sense voltage of V SWITCH, a RECALL cycle will automatically be initiated and will take t RESTORE to complete. If the STK16C68 is in a WRITE state at the end of power-up RECALL, the SRAM data will be corrupted. To help avoid this situation, a 10k Ω resistor should be connected either between W and system V CC or between E and system V CC. SOFTWARE NONVOLATILE STORE The STK16C68 software STORE cycle is initiated by executing sequential 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 initi- ated, 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 impor- tant that no other READ or WRITE accesses inter- vene 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: DEVICE OPERATION |
Similar Part No. - STK16C68-WF25 |
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Similar Description - STK16C68-WF25 |
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