User's Manual

Table Of Contents

TRF7970A

Microcontroller

Drive the MOD pin

according to the data coding

specified by the standard

Decode the subcarrier

information according

to the standard

MOD

(Pin 14)

I/O_6

(Pin 23)

TRF7970A

SLOS743K –AUGUST 2011–REVISED APRIL 2014

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Step 5: Transmit Data Using Direct Mode

The application now has direct control over the RF modulation through the MOD input (see Figure 6-29).

Figure 6-29. Direct Control Signals

The microcontroller is responsible for generating data according to the coding specified by the particular

standard. The microcontroller must generate SOF, EOF, Data, and CRC. In direct mode, the FIFO is not

used and no IRQs are generated. See the applicable ISO standard to understand bit and frame

definitions. As an example of what the developer sees when using DM0 in an actual application, Figure 6-

30 is presented to clearly show the relationship between the MOD pin being controlled by the MCU and

the resulting modulated 13.56-MHz carrier signal.

Figure 6-30. TX Sequence Out in DM0

Step 6: Receive Data Using Direct Mode

After the TX operation is complete, the tag responds to the request and the subcarrier data is available on

pin I/O_6. The microcontroller needs to decode the subcarrier signal according to the standard. This

includes decoding the SOF, data bits, CRC, and EOF. The CRC then needs to be checked to verify data

integrity. The receive data bytes must be buffered locally.

As an example of the receive data bits and framing level according to the ISO14443A standard is shown

in Figure 6-31 (taken from ISO14443 specification and TRF7970A air interface).

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