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STK16CA8 Datenblatt(PDF) 8 Page - Simtek Corporation |
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STK16CA8 Datenblatt(HTML) 8 Page - Simtek Corporation |
8 / 12 page STK16CA8 September 2003 8 Document Control # ML0023 rev 0.1 The STK16CA8 has two separate modes of opera- tion: 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 func- tions are disabled. SRAM READ The STK16CA8 performs a READ cycle whenever E and G are low and W is high. The address specified on pins A 0-16 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 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 new output data appears 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 STK16CA8’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. In order to prevent unneeded STORE operations, automatic STOREs 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 CCX < VSWITCH), 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 STK16CA8 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. SOFTWARE NONVOLATILE STORE The STK16CA8 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 nonvol- atile elements. The program operation copies the SRAM data into nonvolatile memory. Once a STORE cycle is initiated, further input and output are dis- abled 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 4E38 (hex) Valid READ 2. Read address B1C7 (hex) Valid READ 3. Read address 83E0 (hex) Valid READ 4. Read address 7C1F (hex) Valid READ 5. Read address 703F (hex) Valid READ 6. Read address 8FC0 (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, and it is necessary that G be low for the sequence to be DEVICE OPERATION |
Ähnliche Teilenummer - STK16CA8 |
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Ähnliche Beschreibung - STK16CA8 |
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