AN3002

RF password mechanisms

Doc ID 15912 Rev 2

11/22

value of these two bits is used to link a password to the sector as defined in Table 6.

The M24LRxx password protection is organized around a dedicated set of commands plus a

system area of three password blocks where the password values are stored. This system

area is described in Table 7.

The dedicated password commands are:

Write-sector Password

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

system area. This command must be used to update password values. After the write cycle,

the new password value is automatically activated. It is possible to modify a password value

after issuing a valid Present-sector Password command.

On delivery, the three default password values are set to 0000 0000h and are activated.

Lock-sector Password

The Lock-sector Password command is used to set the Sector security status byte of the

After issuing a Lock-sector Password command, the protection settings of the selected

sector are activated. The protection of a locked block cannot be changed in RF mode.

Table 5.

Read / Write protection bit setting

Sector lock

Sector access when password

presented

Sector access when password not

presented

0

xx

Read

Write

Read

Write

1

00

Read

Write

Read

No Write

1

01

Read

Write

Read

Write

1

10

Read

Write

No Read

No Write

1

11

Read

No Write

No Read

No Write

Table 6.

Password Control bits

Password

00

No password protection: Password 0 condition

01

The sector is protected by the Password 1

10

The sector is protected by the Password 2

11

The sector is protected by the Password 3

Table 7.

Password system area

Add

0

7 8

15

16

23

24

31

1

Password 1

2

Password 2

3

Password 3