M24C64-R datasheet(17/45 Pages) STMICROELECTRONICS

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M24C64-W M24C64-R M24C64-F

5.1.3

Write Identification Page (M24C64-D only)

The Identification Page (32 bytes) is an additional page which can be written and (later)

permanently locked in Read-only mode. It is written by issuing the Write Identification Page

instruction. This instruction uses the same protocol and format as Page Write (into memory

array), except for the following differences:

•

Device type identifier = 1011b

•

MSB address bits A15/A5 are don't care except for address bit A10 which must be ‘0’.

LSB address bits A4/A0 define the byte address inside the Identification page.

If the Identification page is locked, the data bytes transferred during the Write Identification

Page instruction are not acknowledged (NoAck).

5.1.4

Lock Identification Page (M24C64-D 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:

•

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

5.1.5

ECC (Error Correction Code) and Write cycling

The ECC is offered only in devices identified with process letter K, all other devices

(identified with a different process letter) do not embed the ECC logic.

The Error Correction Code (ECC) is an internal logic function which is transparent for the

I2C communication protocol.

The ECC logic is implemented on each group of four EEPROM bytes(1). Inside a group, if a

single bit out of the four bytes happens to be erroneous during a Read operation, the ECC

detects this bit and replaces it with the correct value. The read reliability is therefore much

improved.

Even if the ECC function is performed on groups of four bytes, a single byte can be

written/cycled independently. In this case, the ECC function also writes/cycles the three

other bytes located in the same group(1). As a consequence, the maximum cycling budget is

defined at group level and the cycling can be distributed over the 4 bytes of the group: the

sum of the cycles seen by byte0, byte1, byte2 and byte3 of the same group must remain

below the maximum value defined Table 11: Cycling performance.

1. A group of four bytes is located at addresses [4*N, 4*N+1, 4*N+2, 4*N+3], where N is an integer.

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