{|{{Prettytable|width: 700px; font-size: 2em;}}
|''Port''||''A9''||''A8''||''Register''||''Usage in KC Compact''
|-
|&ECxx||0||0||Port B data register||is setup as timer and is connected to the video hardware (?)
|-
|&EDxx||0||1||Port C data register||setup as timer and is connected to the Interrupt hardware
|-
|&EExx||1||0||Control register||control
|-
|&EFxx||1||1||Port A data register)||setup as I/O and is connected to the parallel printer port
|-
|}
(note: A8 is passed through an inverter and this describes the order of the registers in the table compared to the order of the registers in the CIO datasheet)
In the KC Compact:
* Port A is setup as I/O and is connected to the parallel printer port
* Port B is setup as timer and is connected to the video hardware (?)
* Port C is setup as timer and is connected to the Interrupt hardware
On start-up, the KC compact programs the z8536 to the following state: