Texas Instruments TRF7970A Instruction Manual page 53

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6.13.1.3 Initial RF Collision Avoidance (0x04)
This command executes the initial collision avoidance and sends out IRQ after 5 ms from establishing RF
field (so the MCU can start sending commands/data). If the external RF field is present (higher than the
level set in NFC Low Field Detection Level register (0x16)) then the RF field can not be switched on and
hence a different IRQ is returned.
6.13.1.4 Response RF Collision Avoidance (0x05)
This command executes the response collision avoidance and sends out IRQ after 75 µs from establishing
RF field (so the MCU can start sending commands/data). If the external RF field is present (higher than
the level set in NFC Low Field Detection Level register (0x16)) then the RF field can not be switched on
and hence a different IRQ is returned.
6.13.1.5 Response RF Collision Avoidance (0x06, n = 0)
This command executes the response collision avoidance without random delay. It sends out IRQ after 75
µs from establishing RF field (so the MCU can start sending commands/data). If the external RF field is
present (higher than the level set in NFC Low Field Detection Level register (0x16)) then the RF field can
not be switched on and hence a different IRQ is returned.
6.13.1.6 Reset (0x0F)
The reset command clears the FIFO contents and FIFO status register (0x1C). It also clears the register
storing the collision error location (0x0E).
6.13.1.7 Transmission With CRC (0x11)
The transmission command must be sent first, followed by transmission length bytes, and FIFO data. The
reader starts transmitting after the first byte is loaded into the FIFO. The CRC byte is included in the
transmitted sequence.
6.13.1.8 Transmission Without CRC (0x10)
Same as Section 6.13.1.7
6.13.1.9 Delayed Transmission With CRC (0x13)
The transmission command must be sent first, followed by the transmission length bytes, and FIFO data.
The reader transmission is triggered by the TX timer.
6.13.1.10 Delayed Transmission Without CRC (0x12)
Same as Section 6.13.1.9
6.13.1.11 Transmit Next Time Slot (0x14)
When this command is received, the reader transmits the next slot command. The next slot sign is defined
by the protocol selection.
6.13.1.12 Block Receiver (0x16)
The block receiver command puts the digital part of receiver (bit decoder and framer) in reset mode. This
is useful in an extremely noisy environment, where the noise level could otherwise cause a constant
switching of the subcarrier input of the digital part of the receiver. The receiver (if not in reset) would try to
catch a SOF signal, and if the noise pattern matched the SOF pattern, an interrupt would be generated,
falsely signaling the start of an RX operation. A constant flow of interrupt requests can be a problem for
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with CRC excluded.
with CRC excluded.
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SLOS743K – AUGUST 2011 – REVISED APRIL 2014
TRF7970A
TRF7970A
Detailed Description 53