ULA Control Register: Difference between revisions

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|Readable=Yes
|Readable=Yes
|Writable=Yes
|Writable=Yes
|ShortDesc=Disables ULA completely and controls its mixing with Tilemap layer.
|ShortDesc=Disable ULA, controls ULA mixing/blending, enable ULA+
}}
}}
{| class="wikitable"
{| class="wikitable"
! Bit !! Function
! Bit !! Function
|-
|-
| 7 || 1 to disable ULA output
| 7 || 1 to disable ULA output (soft reset = 0)
|-
|-
| 6 || 0 to select the ULA colour for blending in SLU modes 6 & 7
| 6 || 0 to select the ULA colour for blending in SLU modes 6 & 7 (soft reset = 0)
1 to select the ULA/tilemap mix for blending in SLU modes 6 & 7
1 to select the ULA/tilemap mix for blending in SLU modes 6 & 7
|-
|-
| 5-1 || Reserved, must be 0
| 5-4 || Reserved, must be 0
|-
| 3 || ULA+ enable (soft reset = 0)
|-
| 2 || may change (ULA half pixel scroll) (soft reset = 0)
|-
| 1 || Reserved, must be 0
|-
|-
| 0 || 1 to enable stencil mode when both the ULA and tilemap are enabled
| 0 || 1 to enable stencil mode when both the ULA and tilemap are enabled
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|}
|}


Bit 0 can be set to choose stencil mode for the combined output of the ULA and [[Tilemap|tilemap]].
Bit 0 can be set to choose stencil mode for the combined output of the ULA and [[Tilemap]].


Bit 6 determines what colour is used in SLU modes 6 & 7 where the ULA is combined with Layer 2 to generate highlighting effects.
Bit 6 determines what colour is used in SLU modes 6 & 7 where the ULA is combined with Layer 2 to generate highlighting effects.
Default value is 0.

Revision as of 06:56, 12 November 2019

Number TBRegisterNumber::$68
Readable TBRegisterReadable::Yes
Writable TBRegisterWritable::Yes
Short Description ShortDesc::Disable ULA, controls ULA mixing/blending, enable ULA+
Bit Function
7 1 to disable ULA output (soft reset = 0)
6 0 to select the ULA colour for blending in SLU modes 6 & 7 (soft reset = 0)

1 to select the ULA/tilemap mix for blending in SLU modes 6 & 7

5-4 Reserved, must be 0
3 ULA+ enable (soft reset = 0)
2 may change (ULA half pixel scroll) (soft reset = 0)
1 Reserved, must be 0
0 1 to enable stencil mode when both the ULA and tilemap are enabled

(if either are transparent the result is transparent otherwise the result is a logical AND of both colours)

Bit 0 can be set to choose stencil mode for the combined output of the ULA and Tilemap.

Bit 6 determines what colour is used in SLU modes 6 & 7 where the ULA is combined with Layer 2 to generate highlighting effects.