It looks like the image
on the beaglebone website
shows P8_16 as being inaccessible to the PRU, however the pinmux reports that it is accessible as an input only. Additionally, I have verified that PRU0 can read data from this pin.
debian@beaglebone:~$ config-pin -l P8_16
default gpio gpio_pu gpio_pd gpio_input qep pruin
debian@beaglebone:~$ config-pin -i P8_16
Pin name: P8_16
Function if no cape loaded: gpio
Function if cape loaded: default gpio gpio_pu gpio_pd gpio_input qep pruin
Function information: gpio1_14 default gpio1_14 gpio1_14 gpio1_14 gpio1_14 eqep2_index pru0_in14
Kernel GPIO id: 46
PRU GPIO id: 78
I would submit a pull request to update the image, but I'm not sure where I should do so.