AS3955 datasheet(47/111 Pages) AMSCO

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[v1-01] 2015-Apr-29

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AS3955 − Detailed Description

Figure 50:

Data Reception in Extended Mode

MCU to NFC Device Data Flow Protocol

NFC devices can receive data from a MCU through AS3955 by

using standard READ commands.

Prior to writing data into the buffer, the MCU shall issue a Clear

Buffer command to AS3955 to ensure data are correctly

mapped into the buffer. To start data transmission, the MCU

shall issue then a Transmit Buffer command. In this way, the flag

io_data_rdy is set and data can be transmitted to the reader.

The transmission of the data from the tag to the NFC device is

done by issuing a READ command on block FCh. The fourth

block being read during the read command contains the status

flags of the ongoing communication.

NFC devices can receive data from a MCU through AS3955 by

using standard READ commands.

Prior to writing data into the buffer, it is advisable that to issue

a Clear Buffer command to AS3955 to ensure data are correctly

mapped into the buffer. MCU can trigger data transmission by

writing three words of data into the buffer at addresses

FCh-FEh, and issuing a Transmit Buffer command. This will also

set io_data_rdy flag. The transmission of the data from the tag

to the read is done by issuing a read command on word 0xFC.

The NFC device can then retrieve the data from the buffer by

sending a READ command to address FCh. The fourth word

contains the status flags as shown in Figure 51.

PCD

AS3955

ACK

MCU

DATA RD O

WRITE @ FC

Rx end

WRITE @ FD

ACK

WRITE @

FEh

ACK

WRITE @

FFh

ACK

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