Now so on, i see there is no way to read directly the Latch Value for example to the accumulator or any register. I have try some expiriences to read it.....
I also design my Software with an RAM buffer. Only a interrupt routine copy the value to the portspins. So i write always to the RAM. (not for highspeed I/O routines) The advantage is the interrupt routine can check for shorts or do a global I/O enable to some critical hardware. (remember security systems with watchdog function can disable the I/O and so on...
And you have a periodical defined I/O
frequency like a SPS.
But the problem(!) is 4 bytes are only in use for the Ports. 256 bytes are often not enough..!!! (or 128 bytes)

Sascha