AN3408 datasheet(12/38 Pages) STMICROELECTRONICS

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NDEF data

AN3408

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DocID018867 Rev 4

2.3.2

L field format

The L field can be either coded on 1 or 3 bytes, as shown in Table 13.

2.3.3

V field: NDEF message

The V field is composed of a record head byte, the NDEF message and TLV terminator. The

record head byte is described in a): Record head byte.

An application example is given to illustrate a TLV field: it is a URL, as specified in the “URI

Record Type Definition” document (NFC forum). see Chapter 4.2: URI record.

Record head byte

An NDEF message can contain 1 or more NDEF records. The record head byte gives some

information on the current NDEF record.

The different fields of record head byte are described in Table 14.

Type name format field values

The type name format (TNF) is a 3 bits value that indicates the structure of the value of the

type field.

Table 13. L field byte format

Byte format

Byte number

Value

0x00 to 0xFE

0xFF

0x00FF to 0xFFFE(1)

The 0xFF FFFF value is the concatenation of the bytes 0xFF and 0xFFFF.

Table 14. Record head byte fields description

Name

Bit

Function

MB (message begin)

1: This record is the first of NDEF message.

0: This record is not the first of NDEF message.

ME (message end)

1: This record is the last of NDEF message.

: This record is not the last of NDEF message.

CF (chunk flag)

1: this record is the initial or middle record chunk.

0: this record is the terminating record chunk.

SR (short record)

1: the payload(1) length is on one byte.

Payload is NDEF message body.

0: the payload(1) length is more than one byte.

IL (ID_length flag)

1: ID length field is present.

0: ID length field is omitted.

TNF

2:0

TNF indicates the structure of the type field (see Table 15).

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