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AT45DB642D-TU Datasheet(PDF) 15 Page - ATMEL Corporation |
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AT45DB642D-TU Datasheet(HTML) 15 Page - ATMEL Corporation |
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15 / 55 page  15 3542F–DFLASH–09/06 AT45DB642D 9.1 Sector Protection Register The nonvolatile Sector Protection Register specifies which sectors are to be protected or unpro- tected with either the software or hardware controlled protection methods. The Sector Protection Register contains 32 bytes of data, of which byte locations 0 through 31 contain values that specify whether sectors 0 through 31 will be protected or unprotected. The Sector Protection Register is user modifiable and must first be erased before it can be reprogrammed. Table 9-3 illustrates the format of the Sector Protection Register.: Note: 1. The default value for bytes 0 through 31 when shipped from Atmel is 00H. x = don’t care 9.1.1 Erase Sector Protection Register Command In order to modify and change the values of the Sector Protection Register, it must first be erased using the Erase Sector Protection Register command. To erase the Sector Protection Register, the CS pin must first be asserted as it would be with any other command. Once the CS pin has been asserted, the appropriate 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 CFH. After the last bit of the opcode sequence has been clocked in, the CS pin must be deasserted to initiate the internally self-timed erase cycle. The erasing of the Sector Protection Register should take place in a time of t PE, during which time the Status Register will indicate that the device is busy. If the device is powered-down before the completion of the erase cycle, then the contents of the Sector Protec- tion Register cannot be guaranteed. The Sector Protection Register can be erased with the sector protection enabled or disabled. Since the erased state (FFH) of each byte in the Sector Protection Register is used to indicate that a sector is specified for protection, leaving the sector protection enabled during the erasing of the register allows the protection scheme to be more effective in the prevention of accidental programming or erasing of the device. If for some reason an erroneous program or erase com- mand is sent to the device immediately after erasing the Sector Protection Register and before Table 9-2. Sector Protection Register Sector Number 0 (0a, 0b) 1 to 31 Protected See Table 9-3 FFH Unprotected 00H Table 9-3. Sector 0 (0a, 0b) 0a 0b Bit 3, 2 Data Value (Page 0-7) (Page 8-255) Bit 7, 6 Bit 5, 4 Bit 1, 0 Sectors 0a, 0b Unprotected 00 00 xx xx 0xH Protect Sector 0a 11 00 xx xx CxH Protect Sector 0b (Page 8-255) 00 11 xx xx 3xH Protect Sectors 0a (Page 0-7), 0b (Page 8-255)(1) 11 11 xx xx FxH |
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