ST25TV02K datasheet(28/90 Pages) STMICROELECTRONICS

28 / 90 page

Any ST25TV02K/512 that receive a request with the Address_flag set to 1 compares the received Unique ID to its

own. If it matches, then the ST25TV02K/512 execute the request (if possible) and return a response to the VCD

as specified in the command description.

If the UID does not match, then it remains silent.

Non-addressed mode (general request)

When the Address_flag is cleared to 0 (Non-Addressed mode), the request does not contain a UID.

Select mode

When the Select_flag is set to 1 (Select mode), the request does not contain a unique ID. The ST25TV02K/512 in

the Selected state that receives a request with the Select_flag set to 1 executes it and returns a response to the

VCD as specified in the command description.

Only the ST25TV02K/512 in the Selected state answers a request where the Select_flag is set to 1.

The system design ensures that only one ST25TV02K/512 can be in the Select state at a time.

6.2.4

Request format

The request consists of:

•

an SOF

•

flags

•

a command code

•

parameters and data

•

a CRC

•

an EOF

Table 32. General request format

SOF

Request_flags

Command code

Parameters

Data

2 byte CRC

EOF

6.2.5

Request flags

In a request, the “flags” field specifies the actions to be performed by the ST25TV16K/64K and whether

corresponding fields are present or not.

The flags field consists of eight bits. Bit 3 (Inventory_flag) of the request flag defines the contents of the four

MSBs (bits 5 to 8). When bit 3 is reset (0), bits 5 to 8 define the ST25TV16K/64K selection criteria. When bit 3 is

set (1), bits 5 to 8 define the ST25TV16K/64K Inventory parameters.

Table 33. Definition of request flags 1 to 4

Bit No

Flag

Level

Description

Bit 1

Subcarrier_flag (1)

A single subcarrier frequency is used by the ST25TV16K/64K

Two subcarriers are used by the ST25TV16K/64K

Bit 2

Data_rate_flag (2)

Low data rate is used

High data rate is used

Bit 3

Inventory_flag

The meaning of flags 5 to 8 is described in Table 34. Request flags 5 to 8 when

inventory_flag, Bit 3 = 0

The meaning of flags 5 to 8 is described in Table 35. Request flags 5 to 8 when

inventory_flag, Bit 3 = 1

Bit 4

Protocol_extension_flag

No Protocol format extension

Protocol format extension. Reserved for future use.

1. Subcarrier_flag refers to the ST25TV16K/64K-to-VCD communication.

2. Data_rate_flag refers to the ST25TV16K/64K-to-VCD communication.

ST25TV02K ST25TV512

RF protocol description

DS12074 - Rev 11

page 28/90

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