m24256-bw STMicroelectronics, m24256-bw Datasheet - Page 17

• Manufacturer Part Number: m24256-bw
• Description: 512 Kbit And 256 Kbit Serial I?c Bus Eeprom With Three Chip Enable Lines
• Manufacturer: STMicroelectronics

M24512-Dx, M24512-x, M24256-Bx
3.10
3.11
3.12
Identification Page Write (M24512-DR only)
The Identification page is written by issuing an ID Write instruction. This instruction uses the
same protocol and format as the Page Write in memory array, except for the following
differences:
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If the Identification page is locked, the data bytes transferred during the Identification Page
Write instruction are not acknowledged (NoAck).
Lock Identification Page (M24512-DR only)
The Lock Identification Page instruction (Lock ID) permanently locks the Identification page
in read-only mode. The Lock ID instruction is similar to Byte Write (into memory array) with
the following specific conditions:
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If the Identification Page is locked, the data bytes transferred during the ID Write instruction
are not acknowledged (NoAck).
ECC (error correction code) and write cycling
The M24256-Bx, M24512-x, and M24512-DR devices offer an ECC (error correction code)
logic which compares each 4-byte word with its six associated ECC EEPROM bits. As a
result, if a single bit out of 4 bytes of data happens to be erroneous during a Read operation,
the ECC detects it and replaces it by the correct value. The read reliability is therefore much
improved by the use of this feature.
Note however that even if a single byte has to be written, 4 bytes are internally modified
(plus the ECC bits), that is, the addressed byte is cycled together with the other three bytes
making up the word. It is therefore recommended to write by word (4 bytes) in order to
benefit from the larger amount of Write cycles.
The M24256-Bx, M24512-x, and M24512-DR devices are qualified at 1 million (1 000 000)
Write cycles, using a cycling routine that writes to the device by multiples of 4-bytes.
Device Type Identifier = 1011b
Address bit A10 must be ‘0’; all other address bits are don't care
Device Type Identifier = 1011b
Address bit A10 must be ‘1’; all other address bits are don't care
The data byte must be equal to the binary value xxxx xx1x, where x is don't care.
Doc ID 6757 Rev 15
Device operation
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