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AT45DB642D-TU Datasheet(PDF) 16 Page - ATMEL Corporation |
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AT45DB642D-TU Datasheet(HTML) 16 Page - ATMEL Corporation |
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16 / 55 page  16 3542F–DFLASH–09/06 AT45DB642D the register can be reprogrammed, then the erroneous program or erase command will not be processed because all sectors would be protected. Figure 9-2. Erase Sector Protection Register 9.1.2 Program Sector Protection Register Command Once the Sector Protection Register has been erased, it can be reprogrammed using the Pro- gram Sector Protection Register command. To program the Sector Protection Register, the CS pin must first be asserted and the appropri- ate 4-byte opcode sequence must be clocked into the device via the SI or I/O7 - I/O0 pin. The 4- byte opcode sequence must start with 3DH and be followed by 2AH, 7FH, and FCH. After the last bit of the opcode sequence has been clocked into the device, the data for the contents of the Sector Protection Register must be clocked in. As described in Section 9.1, the Sector Protec- tion Register contains 32 bytes of data, so 32 bytes must be clocked into the device. The first byte of data corresponds to sector 0, the second byte corresponds to sector 1, and so on with the last byte of data corresponding to sector 31. After the last data byte has been clocked in, the CS pin must be deasserted to initiate the inter- nally self-timed program cycle. The programming of the Sector Protection Register should take place in a time of t P, during which time the Status Register will indicate that the device is busy. If the device is powered-down during the program cycle, then the contents of the Sector Protection Register cannot be guaranteed. If the proper number of data bytes is not clocked in before the CS pin is deasserted, then the protection status of the sectors corresponding to the bytes not clocked in can not be guaranteed. For example, if only the first two bytes are clocked in instead of the complete 32 bytes, then the protection status of the last 30 sectors cannot be guaranteed. Furthermore, if more than 32 bytes of data is clocked into the device, then the data will wrap back around to the beginning of the register. For instance, if 33 bytes of data are clocked in, then the 33rd byte will be stored at byte location 0 of the Sector Protection Register. If a value other than 00H or FFH is clocked into a byte location of the Sector Protection Register, then the protection status of the sector corresponding to that byte location cannot be guaran- teed. For example, if a value of 17H is clocked into byte location 2 of the Sector Protection Register, then the protection status of sector 2 cannot be guaranteed. The Sector Protection Register can be reprogrammed while the sector protection enabled or dis- abled. Being able to reprogram the Sector Protection Register with the sector protection enabled allows the user to temporarily disable the sector protection to an individual sector rather than dis- abling sector protection completely. Command Byte 1 Byte 2 Byte 3 Byte 4 Erase Sector Protection Register 3DH 2AH 7FH CFH Opcode Byte 1 Opcode Byte 2 Opcode Byte 3 Opcode Byte 4 CS Each transition represents 8 bits SI or IO 7 - IO0 |
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