Sprite Attribute Upload

Number	$xx57
Decimal
Short desc.	Uploads sprite positions, visibility, colour type and effect flags.
Bit Mask	%---- ---- 0101 0111
Readable	No
Writable	Yes
Subsystem	Sprites

Uploads attributes of the sprite slot selected by Sprite Status/Slot Select ($303B / 12347). Attributes are in 4-5 byte blocks sent in the following order; after sending 4 or 5 bytes the address auto-increments to the next sprite. This auto-increment is independent of other sprite ports. The 4-5 bytes are as follows:

Byte 1 is the low bits of the X position. Legal X positions are 0-319 if sprites are allowed over the border or 32-287 if not. The MSB is in byte 3.

Byte 2 is the Y position. Legal Y positions are 0-255 if sprites are allowed over the border or 32-223 if not (with "core 2.00.22" there's now Y8 bit in b0 of byte 5, allowing for positions 0-511, but I'm not sure at this moment what are legal values).

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

Byte 4 is bitmapped:

Bit	Description
7	Enable visibility
6	If 1, the optional 5th attribute byte should follow. If 0, only four attribute bytes are expected.
5-0	Pattern index ("Name")

Optional (when bit 6 is set in byte 4) byte 5 is bitmapped:

Bit	Description
7	If 1, the pattern will be treated as 4-bit colour one (128 bytes), 0 is for 8-bit colour patterns (256 bytes)
6	Chooses top/bottom part of pattern slot (for 4-bit colour patterns)
5	Reserved, use always 0
4-3	x-axis scale factor: %00 = 1x (16 pixels), %01 = 2x, %10 = 4x, %11 = 8x (128 pixels)
2-1	y-axis scale factor: %00 = 1x (16 pixels), %01 = 2x, %10 = 4x, %11 = 8x (128 pixels)
0	MSB of Y coordinate