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Ligne 263 :
Ligne 263 : − === TLV Blocks ===+ − ==== Tag Field ====+ Ligne 278 :
Ligne 278 : − ==== Length Field ====+ Ligne 289 :
Ligne 289 : − ==== Value Field ====+ − ==== Terminator TLV ====+
PN532-RFID-NFC-Format-NDEF (voir la source)
Version du 9 septembre 2015 à 11:04
, 9 septembre 2015 à 11:04→TLV Blocks
In order to store an NDEF Message on the Mifare Classic card, the message needs to be wrapped inside something called a TLV Block. The basic structure of a '''TLV''' Block is described below.
In order to store an NDEF Message on the Mifare Classic card, the message needs to be wrapped inside something called a TLV Block. The basic structure of a '''TLV''' Block is described below.
== TLV Blocks ==
TLV is an abbreviation for three different fields: T for Tag Field, L for Length Field and V for Value Field. A TLV Block consist of one or more bytes, depending on which of these three fields is present. Note that the TLV Block will always be at least one byte since the T Field is mandatory in every case.
TLV is an abbreviation for three different fields: T for Tag Field, L for Length Field and V for Value Field. A TLV Block consist of one or more bytes, depending on which of these three fields is present. Note that the TLV Block will always be at least one byte since the T Field is mandatory in every case.
=== Tag Field ===
The Tag Field (or T Field) is the only mandatory field, and uses a single-byte to identify the type of TLV block accordingly to a pre-determined table of values:
The Tag Field (or T Field) is the only mandatory field, and uses a single-byte to identify the type of TLV block accordingly to a pre-determined table of values:
Terminator 0xFE Last TLV block in the data area</nowiki>
Terminator 0xFE Last TLV block in the data area</nowiki>
=== Length Field ===
The Length Field (or L Field) contains the size (in bytes) of the value field. The Length Field can be organised in two different ways, using either one or three bytes.
The Length Field (or L Field) contains the size (in bytes) of the value field. The Length Field can be organised in two different ways, using either one or three bytes.
Both the one byte and three byte format must be supported for NFC Forum and NDEF compatability.
Both the one byte and three byte format must be supported for NFC Forum and NDEF compatability.
=== Value Field ===
The Value Field (or V Field) is only present if the Length Field (described above) is present and not equal to 0x00. If the Length Field is not equal to 0, the Value Fields will contain N bytes of data in the format indicated by the T Field above.
The Value Field (or V Field) is only present if the Length Field (described above) is present and not equal to 0x00. If the Length Field is not equal to 0, the Value Fields will contain N bytes of data in the format indicated by the T Field above.
The value field is where the payload (an '''NDEF Message''', for example) is stored.
The value field is where the payload (an '''NDEF Message''', for example) is stored.
=== Terminator TLV ===
The Terminator TLV is the last TLV block in the data area, and consist of a single byte: 0x0FE (see the TLV Block Type table above). This TLV Block in mandatory.
The Terminator TLV is the last TLV block in the data area, and consist of a single byte: 0x0FE (see the TLV Block Type table above). This TLV Block in mandatory.