ST25DV04K datasheet(70/200 Pages) STMICROELECTRONICS

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6.5

I2C read operations

Read operation in user memory is performed successfully only if:

•

Area to which the byte belongs is not read protected by I2CSS register.

•

Area to which the byte belongs is read protected by I2CSS register, but I2C security session is open.

Read operations in system memory and dynamic registers are done independently of any protection mechanism,

except I2C_PWD register which needs I2C security session to be open first.

Read operation in fast transfer mode’s mailbox is performed successfully only if fast transfer mode is activated.

If read is not successful, ST25DVxxx releases the bus and I2C host reads byte value FFh.

After the successful completion of a read operation, the device’s internal address counter is incremented by one,

to point to the next byte address.

After an unsuccessful read operation, ST25DVxxx enters in I2C dead state: internal address counter is not

incremented, and ST25DVxxx is waiting for a full new I2C instruction.

6.5.1

Random Address Read

A dummy write is first performed to load the address into this address counter (as shown in Figure 29. Read

mode sequences) but without sending a Stop condition. Then, the bus master sends another Start condition, and

repeats the device select code, with the Read/Write bit (RW) set to 1. The device acknowledges this, and outputs

the contents of the addressed byte. The bus master must not acknowledge the byte, and terminates the transfer

with a Stop condition.

6.5.2

Current Address Read

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

code with the Read/Write bit (RW) 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 29. Read mode sequences, without acknowledging the byte.

ST25DV04K ST25DV16K ST25DV64K

I2C read operations

DS10925 - Rev 9

page 70/200

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