ST25TV02K datasheet(21/90 Pages) STMICROELECTRONICS

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Bit

Type

Name

Function

Factory value

b15-b0

CNT_VAL

Counter value

Note:

Refer to Table 4. System configuration memory map accessible through write_cfg and read_cfg commands for

the CNT_VAL register.

5.7.2

Counter description

A 16 bits counter can track the write events on the NDEF file.

It benefits from an anti-tearing mechanism that ensures the consistency of the counter, even if there is an

electrical problem during its increment.

The value of the counter (CNT_VAL) can be checked by any application, by reading the Counter register.

If enabled (when CNT_EN = 1), the Write counter will be incremented on first successful Write event which

is performed in the user area, inside an RF session (an RF session is entered when ST25TV02K/512 receive

enough power from the RF field). After enabling the counter, the counter will not count until the next RF field on/off

cycle.

The default configuration is with a counter disabled.

The counter cannot be locked. When the counter reach its maximum (216-1) the increment mechanism is blocked.

The counter is cleared and automatically disabled when CNT_CLR is set to 1.

Apart from these procedures, there is no way to act on the value of this counter.

The Read/Write counter can be configured through the Counter Configuration register.

This Counter Configuration register allows to:

•

Enable or disable this counter (CNT_EN)

•

Clear the counter (CNT_CLR)

The Counter Configuration register is protected by the configuration password.

5.8

Inventory Read

ST25TV02K/512 have the ability to perform in a single command Inventory Read (Refer to

Section 6.4.37 Inventory read), an Inventory in accordance with the regular anticollision sequence followed by

a Multiple Block Read, reducing the overall communication time. ST25TV02K/512 return the requested memory

content if ST25TV02K/512 match the mask specified in the command.

When using the Fast Inventory Read (refer to Section 6.4.38 Fast inventory read), the response is twice the data

rate.

5.9

Inventory Initiated

ST25TV02K/512 provide a special feature to improve the inventory time response of moving tags using the

Initiate_flag value. This flag, controlled by the Initiate command (refer to Section 6.4.36 Initiate), allows tags to

answer to Inventory Initiated commands (refer to Section 6.4.35 Inventory Initiated).

For applications where multiple tags are moving in front of a reader, it is possible to miss tags using the standard

inventory command. The reason is that the inventory sequence has to be performed on a global tree search. For

example, a tag with a particular UID value may have to wait the run of a long tree search before being inventoried.

If the delay is too long, the tag may be out of the field before it has been detected.

Using the Initiate command, the inventory sequence is optimized. When multiple tags are moving in front of a

reader, the ones which are within the reader field will be initiated by the Initiate command. In this case, a small

batch of tags will answer to the Inventory Initiated command which will optimize the time necessary to identify all

the tags. When finished, the reader has to issue a new Initiate command in order to initiate a new small batch of

tags which are new inside the reader field.

It is also possible to reduce the inventory sequence time using the Fast Initiate (refer to Section 6.4.34 Fast

Initiate), and Fast Inventory Initiated commands (refer to Section 6.4.33 Fast Inventory Initiated). These

commands allow the ST25TV02K/512 to increase their response data rate by a factor of 2, up to 53 kbit/s.

ST25TV02K ST25TV512

Inventory Read

DS12074 - Rev 11

page 21/90

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