I/O Map
The following table lists the main I/O definitions of the Studio IV.
| Q | Sound on/off, frequency as defined by tone latch |
| EF3 | Key pressed on selected port (key pad 1) |
| EF4 | Key pressed on selected port (key pad 2) |
| OUT 1 | Tone latch, which sets tone frequency |
| OUT 2 | Select key / port |
| OUT 4 | bit 0-2 background colour, bit 3 white foreground, bit 4-5 enable graphics, bit 6 PAL/NTSC |
| OUT 5 | Signal video chip to enable DMA towards the 1802 to fetch display data |