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[v1-10] 2018-Apr-27

AS3956 − Application Information

Following is an example of an NDEF message with one Well

Known URL record, which carries the http://www.ams.com URL:

• In the NDEF message format, the URL above will be

represented by the bytes:

[D1 01 08 55 01 61 6D 73 2E 63 6F 6D]h

• The NDEF Message TLV will have the content: [03 0C D1 01

08 55 01 61 6D 73 2E 63 6F 6D]h; first byte is 03h – T field

value, indicating this is an NDEF Message TLV, second byte

is 0Ch saying the V field is 12 bytes long, the following 12

bytes are the V field holding the NDEF message.

The NDEF message TLV given above will fully occupy the first 3

blocks of the data area and the first two bytes of the 4th block

of the data area (each memory block is 4 bytes long).

Reading/Writing with an NFC Device

NFC devices use the T2T WRITE command to write data into a

T2T platform. The T2T WRITE command consists of 6 bytes, 1st

byte is the command code – A2h, 2nd byte is the block number

where data is to be written and the remaining 4 bytes are the

data content. When the execution of the command is

successful, the tag will return an ACK response – A0h. In case of

failure, a NACK code will be returned (see Error Handling section

of this datasheet for NACK codes). If a write EEPROM command

is the very last command to be sent from an NFC device then it

is good practice to read back the data sent in the last write

command. This is because EEPROM writing takes longer to

execute. A successful read back will confirm the RF field and

hence power was maintained during the EEPROM write and that

the write was successful.

The T2T READ command consists of 2 bytes, first byte is the

command code and is equal to 30h, second byte is the first block

number from which data will be returned. The response, when

successful, will return 4 blocks of data, each block is 4 bytes

long, so 16 bytes of data. In case of error, one byte NACK

response will be returned (see Error Handlingsection of AS3956

datasheet for NACK codes).

AS3956 has to be configured in Extended or Normal mode in

order for an NFC device to write/read NDEF data from the

EEPROM of the tag.

An NFC device has to send 4 write commands to the tag to write

the NDEF Message TLV bytes [03 0C D1 01 08 55 01 61 6D 73 2E

63 6F 6D]hex defined in the section above into blocks 04h-07h:

[A2 04 03 0C D1 01]hex

[A2 05 08 55 01 61]hex

[A2 06 6D 73 2E 63]hex

[A2 07 6F 6D 00 00]hex

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