Difference between revisions of "Clip Window Layer 2 Register"

Latest revision as of 18:43, 14 August 2024

Number	$18
Readable	Yes
Writable	Yes
Short Description	Sets and reads clip-window for Layer 2.

The coordinates are stored under index:

Index	Coordinate
0	X1 position
1	X2 position
2	Y1 position
3	Y2 position

The current read/write index (which coordinate is selected) can be read or reset by Clip Window Control Register ($1C).

Write to register will modify currently selected coordinate, and auto-increment index (wrapping from 3 to 0).

Read from register will only read currently selected coordinate, index is not modified (to read next coordinate, write the current coordinate value back, to increment index).

The coordinate values are 0,255,0,191 after a Reset.

The displayed area is "inclusive", i.e. for default values full 256x192 pixel area is displayed.

For Layer 2 modes (Layer 2 Control Register ($70)) with higher X resolution than 256 the X clip coordinates are doubled (320x256) or quadrupled (640x256) in same way how Sprites and Tilemap clip window works.

@@ Line 5: / Line 5: @@
 |ShortDesc=Sets and reads clip-window for Layer 2.
 }}
-# read/write: X1 position
+The coordinates are stored under index:
-# read/write: X2 position
+{| class="wikitable"
-# read/write: Y1 position
+|-
-# read/write: Y2 position
+! Index !! Coordinate
+|-
+| 0 || X1 position
+|-
+| 1 || X2 position
+|-
+| 2 || Y1 position
+|-
+| 3 || Y2 position
+|}
-The values are 0,255,0,191 after a Reset.
+The current read/write index (which coordinate is selected) can be read or reset by {{NextRegNo|$1C}}.
-The current read/write index (which coordinate is next) can be read or reset by {{NextRegNo|$1C}}.
+Write to register will modify currently selected coordinate, and auto-increment index (wrapping from 3 to 0).
+Read from register will only read currently selected coordinate, index is not modified (to read next coordinate, write the current coordinate value back, to increment index).
+The coordinate values are 0,255,0,191 after a Reset.
+The displayed area is "inclusive", i.e. for default values full 256x192 pixel area is displayed.
+For Layer 2 modes ({{NextRegNo|$70}}) with higher X resolution than 256 the X clip coordinates are doubled (320x256) or quadrupled (640x256) in same way how Sprites and Tilemap clip window works.