r30 and r31 output/input only?

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I noticed that very few PRU 0 r30 pins are hooked up to the Expansion headers (P8/P9) There are some r31 pins , but if I am reading correctly, on the PRU, r31 is for input only. I am a tad confused by that, as I see that UART1 tx is connected to r31 (not sure why the transmitter would be connected to an input).

Just wanted to check, r30 is output and r31 is input only on the PRU?

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Just wanted to check, r30 is output and r31 is input only on the PRU?

In short, yes they are.

If you are about the In/Out use of the registers. There is much more.
For example, R31 could be used as a “zero” source, for single-bit mask composition.