SWCU193A April 2023 – August 2024 CC2340R2 , CC2340R5 , CC2340R5-Q1
When the UART.CTL[1] SIREN bit is set, the IrDA (SIR) encoder and decoder are enabled and provide hardware bit shaping for IrDA communication. In this protocol, from the transmitter perspective, a zero logic level is transmitted as a high pulse of 3/16th duration of the selected baud rate bit period, while logic one levels are transmitted as a static LOW signal.
The SIR decoder converts the IrDA-compliant receive signal into a bit stream for the UART core. The SIR receive logic interprets a high state as a logic one and low pulses as logic zeros.
Setting the UART.CTL SIRLP[2] bit enables low power mode. In the low-power mode, the width of the pulse is set to three times the time period of the IrLPBaud16 signal. The IrLPBaud16 signal is generated by dividing down CLKSVT (48MHz) according to the low-power divisor value written to the UART.UARTILPR register. The low-power divisor value is calculated as follows:
where FIrLPBaud16 is nominally 1.8432MHz.
The divisor must be selected such that 1.42MHz < FIrLPBaud16 < 2.12MHz, which results in a low-power pulse duration of 1.41-2.11μs (three times the period of IrLPBaud16).
Regardless of whether low-power mode is used or not UART.UARTILPR must be configured to generate IrLPBaud16 at the correct frequency to allow a normal-mode UART to receive data from a low-power mode UART, which can transmit pulses as small as 1.41μs. If reception from a low-power mode UART is not required then UART.UARTILPR can be left unconfigured.
The maximum supported bit-rate for IrDA is 115.2Kbps.