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CY14MC256J Datasheet(PDF) 8 Page - Cypress Semiconductor |
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CY14MC256J Datasheet(HTML) 8 Page - Cypress Semiconductor |
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8 / 30 page  CY14MC256J CY14MB256J CY14ME256J Document Number: 001-65233 Rev. *G Page 8 of 30 Memory Control Register The Memory Control Register contains the following bits: ■ BP1:BP0: Block Protect bits are used to protect one-quarter, one-half, or full memory array. These bits can be written through a write instruction to the 0x00 location of the Control Register Slave device. However, any STORE cycle causes transfer of SRAM data into a nonvolatile cell regardless of whether or not the block is protected. The default value shipped from the factory for BP0 and BP1 is ‘0’. SNL (S/N Lock) Bit: Serial Number Lock bit (SNL) is used to lock the serial number. Once the bit is set to ‘1’, the serial number registers are locked and no modification is allowed. This bit cannot be cleared to ‘0’. The serial number is secured on the next STORE operation (Software STORE or AutoStore). If AutoStore is not enabled, user must perform the Software STORE operation to secure the lock bit status. If a STORE was not performed, the serial number lock bit will not survive the power cycle. The default value shipped from the factory for SNL is ‘0’. Command Register The Command Register resides at address “AA” of the Control Registers Slave device. This is a write only register. The byte written to this register initiates a STORE, RECALL, AutoStore Enable, AutoStore Disable and sleep mode operation as listed in Table 5. Refer to Serial Number on page 16 for details on how to execute a command register byte. ■ STORE: Initiates nvSRAM Software STORE. The nvSRAM cannot be accessed for tSTORE time after this instruction has been executed. When initiated, the device performs a STORE operation regardless of whether a write has been performed since the last NV operation. After the tSTORE cycle time is completed, the SRAM is activated again for read and write operations. ■ RECALL: Initiates nvSRAM Software RECALL. The nvSRAM cannot be accessed for tRECALL time after this instruction has been executed. The RECALL operation does not alter the data in the nonvolatile elements. A RECALL may be initiated in two ways: Hardware RECALL, initiated on power-up; and Software RECALL, initiated by a I2C RECALL instruction. ■ ASENB: Enables nvSRAM AutoStore. The nvSRAM cannot be accessed for tSS time after this instruction has been executed. This setting is not nonvolatile and needs to be followed by a manual STORE sequence if this is desired to survive power cycle. The part comes from the factory with AutoStore Enabled and 0x00 written in all cells. ■ ASDISB: Disables nvSRAM AutoStore. The nvSRAM cannot be accessed for tSS time after this instruction has been executed. This setting is not nonvolatile and needs to be followed by a manual STORE sequence if this is desired to survive power cycle. Note If AutoStore is disabled and VCAP is not required, it is required that the VCAP pin is left open. VCAP pin must never be connected to ground. Power-Up RECALL operation cannot be disabled in any case. ■ SLEEP: SLEEP instruction puts the nvSRAM in a sleep mode. When the SLEEP instruction is registered, the nvSRAM takes tSS time to process the SLEEP request. Once the SLEEP command is successfully registered and processed, the nvSRAM toggles HSB LOW, performs a STORE operation to secure the data to nonvolatile memory and then enters into SLEEP mode. Whenever nvSRAM enters into sleep mode, it initiates non volatile STORE cycle which results in losing an Table 2. Control Registers map Address Description Read/Write Details 0x00 Memory Control Register Read/Write Contains Block Protect Bits and Serial Number Lock bit 0x01 Serial Number 8 Bytes Read/Write (Read only when SNL is set) Programmable Serial Number. Locked by setting the Serial Number lock bit in Memory Control Register to ‘1’. 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 Device ID Read only Device ID is factory programmed 0x0A 0x0B 0x0C 0x0D Reserved Reserved Reserved 0xAA Command Register Write only Allows commands for STORE, RECALL, AutoStore Enable/Disable, SLEEP Mode Table 3. Memory Control Register Bits Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 0SNL (0) 0 0 BP1 (0) BP0 (0) 00 Table 4. Block Protection Level BP1:BP0 Block Protection 000 None 1/4 01 0x6000–0x7FFF 1/2 10 0x4000–0x7FFF 1 11 0x0000–0x7FFF Table 5. Command Register bytes Data Byte [7:0] Command Description 0011 1100 STORE STORE SRAM data to nonvolatile memory 0110 0000 RECALL RECALL data from nonvolatile memory to SRAM 0101 1001 ASENB Enable AutoStore 0001 1001 ASDISB Disable AutoStore 1011 1001 SLEEP Enter Sleep Mode for low power consumption |
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