Difference between revisions of "Sprite port-mirror Attribute 2 (with INC) Register"

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After write into sprite-attribute "byte 3" ({{PortNo|$xx57}}), the {{NextRegNo|$34}} is incremented (with all consequences stemming from such action). If the sprite 63 was modified, the result of the increment is officially "undefined behaviour", and code should explicitly set valid 0..63 sprite index before next sprite-attribute manipulation.
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After write into sprite-attribute "byte 3" ({{PortNo|$xx57}}), the {{NextRegNo|$34}} is incremented (with all consequences stemming from such action). If the sprite 127 was modified, the result of the increment is officially "undefined behaviour", and code should explicitly set valid 0..127 sprite index before next sprite-attribute manipulation.

Revision as of 09:10, 27 January 2019

Number $77
Readable No
Writable Yes
Short Description Same as Sprite port-mirror Attribute 2 Register ($37) (write third byte of sprite-attributes), plus increments Sprite port-mirror Index Register ($34)

Byte 3 is bitmapped:

Bit Description
4-7 Palette offset, added to each palette index from pattern before drawing
3 Enable X mirror
2 Enable Y mirror
1 Enable rotation
0 MSB of X coordinate

After write into sprite-attribute "byte 3" (Sprite Attribute Upload ($xx57 / 87)), the Sprite port-mirror Index Register ($34) is incremented (with all consequences stemming from such action). If the sprite 127 was modified, the result of the increment is officially "undefined behaviour", and code should explicitly set valid 0..127 sprite index before next sprite-attribute manipulation.