AN3002

M24LRxx’s conditional memory access

Doc ID 15912 Rev 2

17/22

M24LRxx memory access after a valid Present-sector Password command

After a valid Present-sector Password command, the memory sector accesses are changed

as shown in Table 14: RF memory access condition after a valid Present-sector Password.

The sector 0 can be updated by a write command, the sector 3 is now accessible in read

mode, and the sector 2 is accessible in both read and write modes.

This protection mechanism is submitted to an RF password value. The example above uses

the password value 1 as defined by the Sector security status bits b3 & b4. The M24LRxx

provides 3 different passwords, so that 3 different applications can manage its memory

access conditions.

In the multiple RF password protection scheme, the M24LRxx memory can be divided into 6

different areas using the 4 different passwords conditions listed below:

●

The public EEPROM area, no password protection

●

The public ROM area, controlled by the password 0 condition

●

The non-accessible area controlled by the password 0 condition

●

The “application 1” area protected by the password 1

●

The “application 2” area protected by the password 2

●

The “application 3” area protected by the password 3

It is not mandatory to have contiguous sectors affected to the same area as each individual

sector in the M24LRxx can be set to any one of the 4 password conditions.

Table 14.

RF memory access condition after a valid Present-sector Password

Access condition

M24LRxx user memory

SSS byte

Read and Write

Sector 0

0000 1001b

Read and Write

Sector 1

0000 1011b

Read and Write

Sector 2

0000 1101b

Read only

Sector 3

0000 1111b

Read and Write

…

0000 0000b

Read and Write

Sector 62

0000 0000b

Read and Write

Sector 63

0000 0000b

Not accessible in RF

I2C_Write lock bit area

Not applicable

Write once in RF

Sector_Security_Status area

Not applicable