SRT512 datasheet(18/46 Pages) STMICROELECTRONICS

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Memory mapping

SRT512

18/46

Doc ID 13277 Rev 4

4.4

System area

This area is used to modify the settings of the SRT512. It contains 3 registers:

OTP_Lock_Reg, Fixed Chip_ID and ST Reserved. See Figure 17 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.

Figure 17.

System area

4.4.1

OTP_Lock_Reg

The 16 bits, b31 to b16, of the System area (block address 255) are used as

OTP_Lock_Reg bits in the SRT512. They control the write access to the 16 blocks 0 to 15

as follows:

●

When b16 is at 0, block 0 is write-protected

●

When b17 is at 0, block 1 is write-protected

●

When b18 is at 0, block 2 is write-protected

●

When b19 is at 0, block 3 is write-protected

●

When b20 is at 0, block 4 is write-protected

●

When b21 is at 0, block 5 is write-protected

●

When b22 is at 0, block 6 is write-protected

●

When b23 is at 0, block 7 is write-protected

●

When b24 is at 0, block 8 is 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, the 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 SRT512 in order to load

the block write protection into the logic.

This bit is set by ST during production tests on customer request. It cannot be modified by

the user.

Block

address

255

MSB

32-bit block

LSB

Description

OTP

OTP_Lock_Reg

ST reserved

Fixed Chip_ID

(Option)

ai13505b

b31

b16 b15 b14

b8 b7

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