ST25TB02K datasheet(14/47 Pages) STMICROELECTRONICS

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4.3

System area

This area is used to modify the settings of the ST25TB02K. It contains 2 registers: OTP_Lock_Reg and ST

Reserved. See Table 7. System area for a map of this area.

A Write_block command in this area will not erase the previous contents. Selected bits can thus be set from 1

to 0. All bits previously at 0 remain unchanged. Once all the 32 bits of a block are at 0, the block is empty and

cannot be updated any more.

Table 7. System area

Block Address

MSB

32-bit block

LSB

Description

b31

b24

b23

b16

b15

b14

255

OTP_Lock_Reg

ST reserved

OTP

4.3.1

OTP_Lock_Reg

The 8 bits, b31 to b24, of the System area (block address 255) are used as OTP_Lock_Reg bits in the

ST25TB02K. They control the write access to the 9 EEPROM blocks with addresses 7 to 15 as follows:

•

When b24 is at 0, blocks 7 and 8 are write-protected

•

When b25 is at 0, block 9 is write-protected

•

When b26 is at 0, block 10 is write-protected

•

When b27 is at 0, block 11 is write-protected

•

When b28 is at 0, block 12 is write-protected

•

When b29 is at 0, block 13 is write-protected

•

When b30 is at 0, block 14 is write-protected

•

When b31 is at 0, block 15 is write-protected.

The OTP_Lock_Reg bits cannot be erased. Once write-protected, EEPROM blocks behave like ROM blocks and

cannot be unprotected.

After any modification of the OTP_Lock_Reg bits, it is necessary to send a Select command with a valid Chip_ID

to the ST25TB02K in order to load the block write protection into the logic.

ST25TB02K

System area

DS11469 - Rev 7

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