ST25DV04K datasheet(13/197 Pages) STMICROELECTRONICS

13 / 197 page

4.2.1

User memory areas

The user memory can be split into different areas, each one with a distinct access privilege.

RF and I2C read and write commands are legal only within the same zone:

•

In RF, a multiple read or a multiple write command is not executed and returns the error code 0Fh if

addresses cross the area borders.

•

In I2C, a read data always return FFh after crossing an area border. A write command is not acknowledged

and not executed if the command crosses the area border.

Each user memory area is defined by its ending block address ENDAi. The starting block address is defined by

the end of the preceding area.

There are three ENDAi registers in the configuration system memory, used to define the end block addresses of

Area 1, Area 2 and Area 3. The end of Area 4 is always the last block of memory, and is not configurable.

Figure 8. ST25DVxxx user memory areas

Area1

(8 Blocks/32 Bytes minimum)

Area2

Area3

Area4

ST25DV user memory

ENDA1

ENDA2

ENDA3

Areas limit

registers

Block/Byte 0000h

Last Block/Byte

of user memory

On factory delivery all ENDAi are set to their maximum value, only Area1 exists and includes the full user

memory.

A granularity of 8 blocks (32 bytes) is offered to code area ending points.

An area end limit is coded as follows in ENDAi registers:

•

Last RF block address of area = 8 * ENDAi + 7 → ENDAi = int(Last Areai RF block address / 8)

•

Last I2C byte address of area = 32 * ENDAi + 31 → ENDAi = int(Last Areai I2C byte address / 32)

•

As a consequence, ENDA1 = 0 minimum size of Area 1 is 8 blocks (32 bytes).

Table 3. Maximum user memory block and byte addresses and ENDAi value

Device

Last user memory block address

seen by RF

Last user memory byte address seen

by I2C

Maximum ENDAi value

ST25DV04K-xx

007Fh

01FFh

0Fh

ST25DV16K-xx

01FFh

07FFh

3Fh

ST25DV64K-xx

07FFh

1FFFh

FFh

ST25DV04K ST25DV16K ST25DV64K

User memory

DS10925 - Rev 11

page 13/197

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