M24LR64-R_1004 datasheet(25/126 Pages) STMICROELECTRONICS

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M24LR64-R

System memory area

Doc ID 15170 Rev 9

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4.3

I2C_Write_Lock bit area

In the I2C mode only, it is possible to protect individual sectors against Write operations.

This feature is controlled by the I2C_Write_Lock bits stored in the 8 bytes of the

I2C_Write_Lock bit area starting from the location 2048 (see Table 13). Using these 64 bits,

it is possible to write-protect all the 64 sectors of the M24LR64-R memory.

Each bit controls the I2C write access to a specific sector as shown in Table 13. It is always

possible to unprotect a sector in the I2C mode. When an I2C_Write_Lock bit is reset to 0,

the corresponding sector is unprotected. When the bit is set to 1, the corresponding sector

is write-protected.

In I2C mode, read access to the I2C_Write_Lock bit area is always allowed. Write access

depends on the correct presentation of the I2C password.

To access the I2C_Write_Lock bit area, the device select code used for any I2C command

must have the E2 Chip Enable address at 1.

On delivery, the default value of the 8 bytes of the I2C_Write_Lock bit area is reset to 00h.

4.4

System parameters

The M24LR64-R provides the system area required by the ISO 15693 RF protocol, as

shown in Table 14.

The first 32-bit block starting from I2C address 2304 stores the I2C password. This password

is used to activate/deactivate the write protection of the protected sector in I2C mode. At

power-on, all user memory sectors protected by the I2C_Write_Lock bits can be read but

cannot be modified. To remove the write protection, it is necessary to use the I2C Present

Password described in Figure 8. When the password is correctly presented — that is, when

all the presented bits correspond to the stored ones — it is also possible to modify the I2C

password using the I2C Write Password command described in Figure 9.

The next three 32-bit blocks store the three RF passwords. These passwords are neither

read- nor write- accessible in the I2C mode.

The next 2 bytes are used to store the AFI, at I2C location 2322, and the DSFID, at I2C

location 2323. These 2 values are used during the RF Inventory sequence. They are read-

only in the I2C mode.

The next 8 bytes, starting from location 2324, store the 64-bit UID programmed by ST on the

production line. Bytes at I2C locations 2332 to 2335 store the IC Ref and the Mem_Size data

used by the RF Get_System_Info command. The UID, Mem_Size and IC Ref values are

read-only data.

Table 13.

I2C_Write_Lock bit

I2C byte address

Bits [31:24]

Bits [23:16]

Bits [15:8]

Bits [7:0]

E2 = 1

2048

sectors 31-24

sectors 23-16

sectors 15-8

sectors 7-0

E2 = 1

2052

sectors 63-56

sectors 55-48

sectors 47-40

sectors 39-32

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