M24C64-W datasheet(21/42 Pages) STMICROELECTRONICS

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M24C64-W M24C64-R M24C64-F M24C64-DF

Instructions

Doc ID 16891 Rev 27

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5.2.2

Current Address Read

For the Current Address Read operation, following a Start condition, the bus master only

sends a device select code with the R/W bit set to 1. The device acknowledges this, and

outputs the byte addressed by the internal address counter. The counter is then

incremented. The bus master terminates the transfer with a Stop condition, as shown in

Figure 11, without acknowledging the byte.

5.2.3

Sequential Read

This operation can be used after a Current Address Read or a Random Address Read. The

bus master does acknowledge the data byte output, and sends additional clock pulses so

that the device continues to output the next byte in sequence. To terminate the stream of

bytes, the bus master must not acknowledge the last byte, and must generate a Stop

condition, as shown in Figure 11.

The output data comes from consecutive addresses, with the internal address counter

automatically incremented after each byte output. After the last memory address, the

address counter “rolls-over”, and the device continues to output data from memory address

00h.

5.3

Read 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.

The Identification Page can be read by issuing an Read Identification Page instruction. This

instruction uses the same protocol and format as the Random Address Read (from memory

array) with device type identifier defined as 1011b. The MSB address bits A15/A5 are don't

care, the LSB address bits A4/A0 define the byte address inside the Identification Page. The

number of bytes to read in the ID page must not exceed the page boundary (e.g.: when

reading the Identification Page from location 10d, the number of bytes should be less than

or equal to 22, as the ID page boundary is 32 bytes).

5.4

Read the lock status (M24C64-D only)

The locked/unlocked status of the Identification page can be checked by transmitting a

specific truncated command [Identification Page Write instruction + one data byte] to the

device. The device returns an acknowledge bit if the Identification page is unlocked,

otherwise a NoAck bit if the Identification page is locked.

Right after this, it is recommended to transmit to the device a Start condition followed by a

Stop condition, so that:

●

Start: the truncated command is not executed because the Start condition resets the

device internal logic,

●

Stop: the device is then set back into Standby mode by the Stop condition.

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