M24256E-FDW6TP datasheet(22/46 Pages) STMICROELECTRONICS

22 / 46 page

6.6

Read the lock status

The locked/unlocked status of the identification page can be checked by transmitting a specific truncated

command.

Following a start condition the bus master sends a device select code with the R/W bit (RW) set to 0. The device

acknowledges this and waits for the address bytes where the identification page is located. The device responds

to each address byte with an acknowledge bit, and then waits for the data byte. See in Section 5.5 Device

addressing (Table 5, Table 6 and Table 7) how to address the identification page.

The device returns an acknowledge bit after the data byte if the identification page is unlocked as shown in

Figure 13, otherwise a NoAck bit as shown in Figure 14, 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.

Figure 13. Read lock status with identification page unlocked

Dev sel

Byte addr

Data in

ACK

Figure 14. Read lock status with identification page locked

Dev sel

Byte addr

Data in

ACK

NOACK

M24256E-F

Read the lock status

DS12687 - Rev 3

page 22/46

M24256E-FDW6TP Datasheet(PDF) 22 Page - STMicroelectronics