Peripheral 4 Register
From SpecNext official Wiki
| Number | $09 |
|---|---|
| Readable | Yes |
| Writable | Yes |
| Short Description | Sets scanlines, AY mono output, Sprite-id lockstep, disables Kempston and divMMC ports. |
| Bit | Function |
|---|---|
| 7 | Enables AY2 "mono" output (A+B+C is sent to both R and L channels, makes it a bit louder than stereo mode). |
| 6 | Enables AY1 "mono" output (1 = mono, 0 default) |
| 5 | Enables AY0 "mono" output |
| 4 | Sprite id lockstep (1 = Sprite port-mirror Index Register ($34) and Sprite Status/Slot Select ($303B / 12347) are in lockstep, 0 default) |
| 3 | Disables Kempston mouse port ($DF) if set |
| 2 | Disables divMMC ports ($E3, $E7, $EB) if set |
| 1-0 | scanlines configuration (0 after a PoR or Hard-reset):
%00 = scanlines off, %01 = scanlines 75%, %10 = scanlines 50%, %11 = scanlines 25% |