LRIS2K_08 datasheet(17/102 Pages) STMICROELECTRONICS

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LRIS2K

LRIS2K block security

17/102

The LRIS2K password protection is organized around a dedicated set of commands plus a

system area of four password blocks where the password values and the Kill code are

stored. Each password block also has a Protect Status area, making it possible to set the

Read / Write access right of each individual block. This system area is described in Table 7.

The dedicated password commands are:

●

Write Password:

The Write Password command is used to write a 32-bit block into the password system

area. This command must be used to write or update password values and to set the

kill code. After the write cycle, the password block, or the kill code, must be activated by

issuing the Lock password command. Depending on the Read/Write access set in the

Protect Status area, it is possible to modify a password value after issuing a valid

Present Password command.

●

Lock Password:

The Lock Password command is used to set the Protect Status area of the selected

block. Bits b4 to b1 of the Protect Status are affected by the Lock Password command.

The Block Lock bit, b0, is set to ‘1’ automatically. After issuing a Lock Password

command, the protection settings of the selected block are activated. The protection of

a locked block cannot be changed. A Lock Password command sent to a locked block

returns an error code.

The Lock Password command is also used to set the Protect Status areas of the

password blocks. RFU bit 8 of the Request_flag is used to select either the memory

area (bit 8 = ‘0’) or the password area (bit 8 = ‘1’).

●

Present Password:

The Present Password command is used to present one of the three passwords to the

LRIS2K in order to modify the access rights of all the memory blocks linked to that

password (Table 5) including the password itself. If the presented password is correct,

the access rights remain activated until the tag is powered off or until a new Present

Password command is issued.

Table 7.

Password system area

Add

7 8

15 16

Protect status

Kill code

5 bits

Password 1

5 bits

Password 2

5 bits

Password 3

5 bits

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