SR176_07 datasheet(21/35 Pages) STMICROELECTRONICS

21 / 35 page

SR176

Device operations (instructions)

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5.7

PROTECT_BLOCK

Command Code = 09h,0Fh,00h,LOCK_REG

Prior to any PROTECT_BLOCK command, the SR176 must have been set into the

SELECTED state.

The PROTECT_BLOCK command allows the write access to be blocked to memory blocks

4 to 15. It must be followed by a SELECT() command. This re-initializes the write protection

conditions to blocks 4 to 15. Until then, the new protection setting is not taken into account

by the SR176 logic. The SR176 does not generate any response when it executes a

PROTECT_BLOCK command (Figure 32). The reader must use the GET_PROTECTION

command to get the information on the protection status.

The OTP LOCK_REG controls the write-protection on blocks 4 to 15, and is, itself, One-

Time Programmable. Each ‘1’ in the LOCK_REG parameter indicates that the

corresponding bit in the OTP LOCK_REG should be set. Each ‘0’ indicates that the

corresponding bit should be left unchanged. Once a bit in the OTP LOCK_REG has been

set to ‘1’, it is not possible to reset it to ‘0’ and the corresponding memory blocks are forever

write protected (and behaves like ROM).

Request parameters (Figure 31):

●

LOCK_REG (Table 3)

Figure 31.

PROTECT_BLOCK request format

Table 3.

Bits in the LOCK_REG parameter, and in the OTP LOCK_REG Register

Lock Reg

Parameter Bit

Meaning

Block 15 Bit

Meaning

1: set b15 of Block 15 to ‘1’

0: leave it unchanged

b15

1: Write-Protect Blocks 14 and 15

0: Allow write access

1: set b14 of Block 15 to ‘1’

0: leave it unchanged

b14

1: Write-Protect Blocks 12 and 13

0: Allow write access

1: set b13 of Block 15 to ‘1’

0: leave it unchanged

b13

1: Write-Protect Blocks 10 and 11

0: Allow write access

1: set b12 of Block 15 to ‘1’

0: leave it unchanged

b12

1: Write-Protect Blocks 8 and 9

0: Allow write access

1: set b11 of Block 15 to ‘1’

0: leave it unchanged

b11

1: Write-Protect Blocks 6 and 7

0: Allow write access

1: set b10 of Block 15 to ‘1’

0: leave it unchanged

b10

1: Write-Protect Blocks 4 and 5

0: Allow write access

1: set b9 of Block 15 to ‘1’

0: leave it unchanged

1: Write-Protect Blocks 2 and 3

0: Allow write access

1: set b8 of Block 15 to ‘1’

0: leave it unchanged

1: Write-Protect Blocks 0 and 1

0: Allow write access

SOF

CRCL

CRCH

EOF

AI07711B

LOCK_REG

00h

8 bIts

PROTECT_BLOCK

09h

0Fh

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