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CY14B104K_1106 Datasheet(PDF) 5 Page - Cypress Semiconductor |
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CY14B104K_1106 Datasheet(HTML) 5 Page - Cypress Semiconductor |
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5 / 35 page  CY14B104K, CY14B104M Document #: 001-07103 Rev. *U Page 5 of 35 chip. A pull-up should be placed on WE to hold it inactive during power-up. This pull-up is effective only if the WE signal is tristate during power-up. Many MPUs tristate their controls on power-up. This should be verified when using the pull-up. When the nvSRAM comes out of power-on-RECALL, the MPU must be active or the WE held inactive until the MPU comes out of reset. To reduce unnecessary non-volatile STOREs, AutoStore, and Hardware STORE operations are 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 is monitored by the system to detect if an AutoStore cycle is in progress. Hardware STORE (HSB) Operation The CY14B104K/CY14B104M provides the HSB pin to control and acknowledge the STORE operations. The HSB pin is used to request a Hardware STORE cycle. When the HSB pin is driven LOW, the CY14B104K/CY14B104M conditionally initiates a STORE operation after tDELAY. An actual STORE cycle begins only if a write to the SRAM has taken place since the last STORE or RECALL cycle. The HSB pin also acts as an open drain driver (internal 100 k weak pull-up resistor) that is internally driven LOW to indicate a busy condition when the STORE (initiated by any means) is in progress. Note After each Hardware and Software STORE operation HSB is driven HIGH for a short time (tHHHD) with standard output high current and then remains HIGH by internal 100 k pull-up resistor. SRAM write operations that are in progress when HSB is driven LOW by any means are given time (tDELAY) to complete before the STORE operation is initiated. However, any SRAM write cycles requested after HSB goes LOW are inhibited until HSB returns HIGH. In case the write latch is not set, HSB is not driven LOW by the CY14B104K/CY14B104M. But any SRAM read and write cycles are inhibited until HSB is returned HIGH by MPU or other external source. During any STORE operation, regardless of how it is initiated, the CY14B104K/CY14B104M continues to drive the HSB pin LOW, releasing it only when the STORE is complete. Upon completion of the STORE operation, the nvSRAM memory access is inhibited for tLZHSB time after HSB pin returns HIGH. Leave the HSB unconnected if it is not used. Hardware RECALL (Power-Up) During power-up or after any low power condition (VCC<VSWITCH), an internal RECALL request is latched. When VCC again exceeds the VSWITCH on powerup, a RECALL cycle is automatically initiated and takes tHRECALL to complete. During this time, the HSB pin is driven LOW by the HSB driver and all reads and writes to nvSRAM are inhibited. Software STORE Data is transferred from the SRAM to the non-volatile memory by a software address sequence. The CY14B104K/CY14B104M Software STORE cycle is initiated by executing sequential CE or OE controlled read cycles from six specific address locations in exact order. During the STORE cycle, an erase of the previous non-volatile data is first performed, followed by a program of the non-volatile elements. After a STORE cycle is initiate, 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 is aborted and no STORE or RECALL takes place. To initiate the Software STORE cycle, the following read sequence must be performed: 1. Read address 0x4E38 Valid READ 2. Read address 0xB1C7 Valid READ 3. Read address 0x83E0 Valid READ 4. Read address 0x7C1F Valid READ 5. Read address 0x703F Valid READ 6. Read address 0x8FC0 Initiate STORE cycle The software sequence may be clocked with CE controlled reads or OE controlled reads, with WE kept HIGH for all the six READ sequences. After the sixth address in the sequence is entered, the STORE cycle commences and the chip is disabled. HSB is driven LOW. After the tSTORE cycle time is fulfilled, the SRAM is activated again for the read and write operation. Software RECALL Data is transferred from the non-volatile 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, perform the following sequence of CE or OE controlled read operations: 1. Read address 0x4E38 Valid READ 2. Read address 0xB1C7 Valid READ 3. Read address 0x83E0 Valid READ 4. Read address 0x7C1F Valid READ 5. Read address 0x703F Valid READ 6. Read address 0x4C63 Initiate RECALL cycle Internally, RECALL is a two step procedure. First, the SRAM data is cleared; then, the non-volatile information is transferred into the SRAM cells. After the tRECALL cycle time, the SRAM is again ready for read and write operations. The RECALL operation does not alter the data in the non-volatile elements. [+] Feedback |
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