| Bits | Description |
|---|
| 7 | Disable ULA output (soft reset = 0) |
| 6:5 | Blending in SLU modes 6 & 7 (soft reset = 0)
= 00 for ula as blend colour
= 10 for ula/tilemap mix result as blend colour
= 11 for tilemap as blend colour
= 01 for no blending |
| 4 | Cancel entries in 8x5 matrix for extended keys |
| 3 | ULA+ enable (soft reset = 0) |
| 2 | ULA half pixel scroll (may change) (soft reset = 0) |
| 1 | Reserved, must be 0 |
| 0 | Enable stencil mode when both the ULA and tilemap are enabled (soft reset = 0) |
Notes:
(if either are transparent the result is transparent otherwise the result is a logical AND of both colours)