Up to nine 8-bit I/O ports are implemented: P1 through P9 are complete except P5.2, and port PJ contains four individual I/O ports.

• All individual I/O bits are independently programmable.
• Any combination of input, output, and interrupt conditions is possible.
• Programmable pullup or pulldown on all ports.
• Programmable drive strength on all ports.
• Edge-selectable interrupt input capability for all the eight bits of ports P1, P2, P3, and P4.
• Read and write access to port-control registers is supported by all instructions.
• Ports can be accessed byte-wise (P1 through P9) or word-wise (P1 through P8) in pairs (PA through PD).