NAME   rev ADDR type chip Description
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SPRxDATA  144  W      D    Sprite x image data register A
SPRxDATB  146  W      D    Sprite x image data register B

	These registers buffer the sprite image data.They are
	usually loaded by the sprite DMA channel but may be
	loaded by either processor at any time. When a horizontal
	coincidence occurs the buffers are dumped into shift
	registers and serially outputed to the display, MSB first
	on the left.
	NOTE: Writing to the A buffer enables (arms) the sprite.
	Writing to the SPRxCTL registers disables the sprite.
	If enabled, data in the A and B buffers will be output
	whenever the beam counter equals the sprite horizontal
	position value in the SPRxPOS register. In lowres mode,
	1 sprite pixel is 1 bitplane pixel wide.In HRES and
	SHRES mode, 1 sprite pixel is 2 bitplane pixels.
	The DATB bits are the 2SBs (worth 2) for the color registers,
	and MSB for SHRES. DATA bits are LSBs of the pixels.