SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
Serial data from the transmit state-machine are encoded to transmit data to the optoelectronics. While the TX FIFO output is high, the TX line is always low, and the counter used to form a pulse on TX is cleared continuously.
After the TX FIFO output resets to 0, TX rises on the falling edge of the seventh 16XCLK. On the falling edge of the tenth 16XCLK pulse, TX falls, creating a 3-clock-wide pulse. While the TX FIFO output stays low, a pulse is transmitted during the seventh clock to the tenth clock of each 16-clock bit cycle.
Figure 12-389 shows the IrDA SIR encoding mechanism.