SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
In TX mode, the PERIF<m>_CLK begins after the firmware loads the TX FIFO and sets either r31[20] (tx_global_go) or r30[17-16] (tx_channel_go) to 1h. After the “go” bit is set, the delay1 (wire delay) compensation counter for each channel begins. After delay1 is complete, PERIF<m>_CLK is driven low and then the delay2 (tst) counter begins. After the delay2 counter expires, the PERIF<m>_CLK starts running (first low and then high). Therefore, first rising edge of PERIF<m>_CLK (measured from the go bit) = delay1 (tx wire delay) + delay2 (tst_counter delay) + half of the 1x clock frequency (since the clock starts low).
Figure 7-32 shows the start condition for TX mode. As shown in the figure, the default value of clock is high. The PRU-ICSS CFG register space has additional registers for controlling the TX start timing delay values: