| Bits | Description |
|---|
| 0 | port e3 divmmc control |
| 1 | multiface (two variable ports) |
| 2 | port 103b,113b i2c |
| 3 | port e7,eb spi |
| 4 | port 133b,143b,153b,163b uart |
| 5 | port fadf,fbdf,ffdf mouse (also disables kempston alias on port df) |
| 6 | port 57,5b,303b sprites |
| 7 | port 123b layer2 |
Notes:
The internal port decoding enables always apply.
When the expansion bus is on, the expansion port decoding enables are logically ANDed with the internal enables.
A zero bit indicates the internal device is disabled. If the expansion bus is on, this allows io cycles for
disabled ports to propagate to the expansion bus, otherwise corresponding io cycles to the expansion bus are filtered.