TRF796xA
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)
IO_6
(pin 23)
37
SLOS758G – DECEMBER 2011 – REVISED MARCH 2020
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Detailed Description
Copyright © 2011–2020, Texas Instruments Incorporated
NOTE
The write command should not be terminated with a Stop condition (for example, in SPI
mode this is done by bringing the SS line high after the register write), because the Stop
condition terminates the direct mode and clears bit 6 of the Chip Status Control register
(0x00), making it a 0.
Figure 6-21. Entering Direct Mode 0
Step 5:
Transmit data using direct mode
The user now has direct control over the RF modulation through the MOD input.
Figure 6-22. Control of RF Modulation Using MOD
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.
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 must decode the subcarrier signal according to the standard. This includes
decoding the SOF, data bits, CRC, and EOF. The CRC then must be checked to verify data integrity. The
receive data bytes must be buffered locally.
shows an example of the receive data bits and framing level according to the ISO/IEC 14443
A standard (sourced from the ISO/IEC 14443 specification and TRF7963A air interface).
