AS3911 datasheet(146/159 Pages) AMSCO

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[v2-11] 2016-Jun-13

AS3911 − Application Information

Stream Mode and Transparent Mode

Standard and custom 13.56 MHz RFID reader protocols, which

are not supported by the AS3911 framing, can be realized using

the AS3911 AFE and framing implemented in the external

microcontroller.

Transparent Mode

After sending the direct command Transparent Mode the

external microcontroller directly controls the transmission

modulator and gets the Receiver output (control logic becomes

“transparent”).

The Transparent Mode is entered on rising edge of signal /SS

after sending the command Transparent Mode and is

maintained as long as the signal /SS is kept high. Before sending

the direct command Transparent Mode the Transmitter and

Receiver have to be turned on, the AFE has to be configured

properly.

While the AS3911 is in the Transparent Mode the AFE is

controlled directly through SPI interface:

• Transmitter modulation is controlled by pin MOSI (high is

modulator on)

• Signal rx_on is controlled by pin SCLK (high enables RSSI

and AGC)

• Output of Receiver AM demodulation chain (digitized

sub-carrier signal) is sent to pin MISO

• Output of Receiver PM demodulation chain (digitized

sub-carrier signal) is sent to pin IRQ

By controlling the rx_on advanced Receiver features like the

RSSI and AGC can be used. The receiver channel selection bits

are valid also in Transparent mode, therefore it is possible to

use only one of the two channel outputs. In case single channel

is selected it is always multiplexed to MISO, while IRQ is kept

low.

Configuration bits related to the ISO mode, framing and FIFO

are of course meaningless in Transparent Mode, all other

configuration bits are respected.

Use of Transparent Mode to implement active peer to peer

(NFC) communication:

The framing implemented in the AS3911 supports all active

modes according to the NFCIP-1 specification (ISO/IEC

18092:2004). In case any amendments to this specification or

some custom active NFC communication need to be

implemented Transparent mode can be used.

There is no special NFC active communication transparent

mode, controlling of the Tx modulation and the Rx is done as

described above.

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