Accessing the M24LRxx memory

AN3163

4/13

Doc ID 17157 Rev 2

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Accessing the M24LRxx memory

Access to the memory contents of the M24LRxx dual-interface memory is a three-step

process:

1.

Inventory of the tags present in the reader field:

This is performed by ISO 15693 RF readers, by using the standard Inventory

command or, if the population is already known, by issuing a product-dedicated

command like Initiate, Inventory Initiated, Fast Initiate or Fast Inventory Initiated. These

commands are all available with the M24LRxx.

At this step, ISO 15693 RF readers knows all tags present in its RF field.

The unique identifier (UID) specifies the chip provider, and the data storage format

identifier (DSFID) indicates the data storage organization.

Your ISO 15693 RF reader is now ready to manage the tag population by using the

mandatory or optional commands (Select, Stay Quiet, Reset to Ready) to access a

single tag (M24LRxx).

2.

Recognition of the chip and its data structure:

Once the tag has been isolated, the ISO 15693 RF reader can access it and get an

overview of the device capability by using the Get System Info command.

The “memory size” of the M24LRxx needs to be coded on 3 bytes. To tell the

ISO 15693 RF reader that it will receive one more byte than usual, the Get System Info

command requests the setting of the Protocol_Extension _flag (bit 4) to ‘1’ in the

Request_flag byte preceding the command code. (See Table 5: Definition of request

flags when the Inventory_flag is NOT set.)

An ISO 15693 RF reader looking for M24LRxx devices has to issue the Get System

Info command with the Protocol_Extension _flag at ‘1’ to receive a valid response. (The

reader can also alternate the value of the Protocol_Extension_flag, to detect other

devices.)

Table 2.

Inventory request format

Request

SOF

Request_flags Inventory

Optional

AFI

Mask

length

Mask

value

CRC16

Request

EOF

8 bits

01h

8 bits

8 bits

0 - 64 bits

16 bits

Table 3.

Get System Info request format

Request

SOF

Request

1.

See Table 5: Definition of request flags when the Inventory_flag is NOT set.

Get System

Info

2.

Gray means that the field is optional.

CRC16

Request

EOF

8 bits

2Bh

64 bits

16 bits