Internal Port Decoding b8-15 Register
From SpecNext official Wiki
| Number | $83 |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Enabling internal ports decoding |
| Bit | Description |
|---|---|
| 7 | (bit 15) Enabling Layer 2 Access Port ($123B / 4667) |
| 6 | (bit 14) Enabling Sprite Attribute Upload ($xx57 / 87), Sprite Pattern Upload ($xx5B / 91) and Sprite Status/Slot Select ($303B / 12347) |
| 5 | (bit 13) Enabling Kempston Mouse Buttons ($FADF / 64223), Kempston Mouse X ($FBDF / 64479) and Kempston Mouse Y ($FFDF / 65503) |
| 4 | (bit 12) Enabling UART TX ($133B / 4923), UART RX ($143B / 5179) and UART Control ($153B / 5435) (UART) |
| 3 | (bit 11) Enabling ($xxE7) and ($xxEB) (SPI) |
| 2 | (bit 10) Enabling I2C clock ($103B / 4155) and I2C data ($113B / 4411) |
| 1 | (bit 9) Enabling Multiface (two variable ports) |
| 0 | (bit 8) Enabling ($xxE3) (DivMMC control) |
All bits are set to 1 upon soft reset.
(note: Next registers with number higher than $7F are inaccessible from Copper code)