Keithley PIO-96 Instruction Manual page 34

B-4 I/O Address Map
Table B-3 shows example control-byte codes for Mode 0.
Table B-3
Example control bytes for mode 0
Control byte (hexadecimal)
80
81
82
8B
9B
Etc.... (there are 15 combinations in Mode 0)
When a port is configured as an output, the data that the port outputs can be returned by reading
the same location. However, this may not reflect the actual state of the output lines if one or
more is shorted. The state of the output latch is being read, not the buffered output lines.
PIO-96 User's Manual
Configuration
PA, PB & PC all outputs
PA, PB, PC-upper outputs, PC-lower input
PA & PC outputs, PB input
PA output, PB & PC inputs
PA, PB & PC all inputs