Texas Instruments TRF7960A Manual page 40

TRF7960A
SLOS732G – JUNE 2011 – REVISED MARCH 2020
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.
Step 5: Transmit data using direct mode
The user now has direct control over the RF modulation through the MOD input.
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.
Figure 6-29 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 TRF7960A air interface).
40 Detailed Description
Figure 6-27. Entering Direct Mode 0
TRF796xA
MOD
(pin 14)
IO_6
(pin 23)
Figure 6-28. Control of RF Modulation Using MOD
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NOTE
Microcontroller
Drive the MOD pin
according to the data-coding
specified by the standard
Decode the subcarrier
information according
to the standard
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