4.1 Active Communication

The TRF7970A ISO Control register (0x01) sets the modulation of the transceiver's RF field when is in initiator mode or active NFC target. The NFC initiator and active target for baud rate of 106 kbps can be achieved by initializing the transceiver as a NFC-A RFID reader (0x08). Each time the transceiver finishes sending a command while being an initiator and active Target it must:

1. Turn off the field by modifying the ISO Control register → 0x21 (passive target).
2. Write to the RX Special Setting register (0x0A) → 0x30 (band-pass 450 kHz to 1.5 MHz and band-pass 100 kHz to 1.5 MHz).
3. Write to the Adjustable FIFO IRQ Levels register (0x14) → 0x0F (IRQ triggered when there are 96 bytes in FIFO during RX or 32 bytes during TX).