25.3.3.2.7 IRCOM Mode of Operation

The USART peripheral can be configured in Infrared Communication mode (IRCOM) which is IrDA® 1.4 compatible with baud rates up to 115.2 kbps. When enabled, the IRCOM mode enables infrared pulse encoding/decoding for the USART.

Figure 25-13. Block Diagram

The USART is set in IRCOM mode by writing 0x02 to the CMODE bits in the USARTn.CTRLC register. The data on the TXD/RXD pins are the inverted values of the transmitted/received infrared pulse. It is also possible to select an event channel from the Event System as an input for the IRCOM receiver. This enables the IRCOM to receive input from the I/O pins or sources other than the corresponding RXD pin. This will disable the RxD input from the USART pin.

For transmission, three pulse modulation schemes are available:

  • 3/16 of the baud rate period
  • Fixed programmable pulse time based on the peripheral clock frequency
  • Pulse modulation disabled

For the reception, a fixed programmable minimum high-level pulse-width for the pulse to be decoded as a logical ‘0’ is used. Shorter pulses will then be discarded, and the bit will be decoded to logical ‘1’ as if no pulse was received.

When IRCOM mode is enabled, Double-Speed mode cannot be used for the USART.