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STK11C68-LF35 Datasheet(PDF) 8 Page - Simtek Corporation |
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STK11C68-LF35 Datasheet(HTML) 8 Page - Simtek Corporation |
8 / 16 page 8 February, 2007 Document Control #ML0007 Rev 0.3 STK11C68 (SMD5962–92324) The STK11C68 is a versatile memory chip that pro- vides several modes of operation. The STK11C68 can operate as a standard 8K x 8 SRAM. It has an 8K x 8 Nonvolatile Elements shadow to which the SRAM information can be copied or from which the SRAM can be updated in nonvolatile mode. NOISE CONSIDERATIONS Note that the STK11C68 is a high-speed memory and so must have a high-frequency bypass capaci- tor of approximately 0.1 μF connected between Vcc 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. SRAM READ The STK11C68 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. 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. SOFTWARE NONVOLATILE STORE The STK11C68 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: 1. Read address 0000 (hex) Valid READ 2. Read address 1555 (hex) Valid READ 3. Read address 0AAA (hex) Valid READ 4. Read address 1FFF (hex) Valid READ 5. Read address 10F0 (hex) Valid READ 6. Read address 0F0F (hex) Initiate STORE cycle The software sequence must be clocked with E con- trolled 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 t STORE 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 soft- ware STORE initiation. To initiate the RECALL cycle, the following sequence of READ operations must be performed: 1. Read address 0000 (hex) Valid READ 2. Read address 1555 (hex) Valid READ 3. Read address 0AAA (hex) Valid READ 4. Read address 1FFF (hex) Valid READ 5. Read address 10F0 (hex) Valid READ 6. Read address 0F0E (hex) Initiate RECALL cycle DEVICE OPERATION |
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