SRI512_08 datasheet(19/47 Pages) STMICROELECTRONICS

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SRI512

Memory mapping

19/47

4.4

System area

This area is used to modify the settings of the SRI512. It contains 3 registers:

OTP_Lock_Reg, Fixed Chip_ID and ST Reserved. See Figure 18 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 18.

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 SRI512. 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 SRI512 in order to load

the block write protection into the logic.

Block

Address

255

MSb

32-bit Block

LSb

Description

OTP

OTP_Lock_Reg

ST Reserved

Fixed Chip_ID

(Option)

ai12374b

b31

b16 b15 b14

b8 b7

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