AS3909 datasheet(58/77 Pages) AMSCO

58 / 77 page

AS3909/AS3910 – 58

ams Datasheet, Confidential: 2013-Oct [3-02]

A p pl i c at io n I n f o r m at i o n

When all the data is transmitted an interrupt is sent to

inform the microcontroller that transmission is finished

(INTR due to end of transmission)

When the reception of part2 of the bit oriented

anticollision frame is finished and there was no collision

detected, data is put in the FIFO and an interrupt is sent

to microcontroller (INTR due to end of receive),

additionally the FIFO Status Register displays the number

of bytes in the FIFO, so the microcontroller can

proceeded with downloading data from the FIFO.

Sequence in case of a split byte (no collision during transponder

response):

Send the direct command Clear

Define the number of full bytes and the number of bits

in the split byte to be transmitted in the registers #0B

and #0C (bits ntx define the number of full bytes, bits

nbtx in register #0B define the number of bits in the split

byte). Bit 0 (antcl) of register #0B has to be additionally

set to 1 to indicate that anticollision frame is sent.

Write the bytes to be transmitted in FIFO. Since the SPI

communication is byte oriented 8 bits have to

transferred also for split byte (sent last), the MSB bits of

split byte which are not transmitted are don’t care.

Send the direct command Transmit Without CRC

When all the data is transmitted an interrupt is sent to

inform the microcontroller that the transmission is

finished (INTR due to end of transmission)

When the reception of part2 of the bit oriented

anticollision frame is finished and there was no collision

detected, data is put in the FIFO and an interrupt is sent

to the microcontroller (INTR due to end of receive),

additionally the FIFO Status Register displays the number

of bytes in the FIFO so the microcontroller can

proceeded with downloading data from the FIFO. First

downloaded byte contains second part of the split byte,

so only the MSB part of byte which was not sent during

transmit is valid.

Collision Detection

The AS3909/10 Framing block is able to detect the bit collision

in case of presence of more ISO-14443A transponders. This

feature is very useful during the select sequence. The collision

is detected during the ANTICOLLISION command (different

transponders have different UIDs); it may already be detected

in the ATQA (answer to REQA or WUPA). When the bit collision

is detected an interrupt is sent (INTR due to collision) and the

bit at which collision occurred is indicated in the Collision

AS3909/10 by bit 0 of register #0B) the bit collision position

displayed in Collision Register is counted from beginning of

anticollision frame (including the part which is transmitted).

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