NAME   rev ADDR type chip Description
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SPRHPTH  H  1E8  W   A    UHRES sprite pointer (high 5 bits)
SPRHPTL  H  1EA  W   A    UHRES sprite pointer (low 15 bits)

	This pointer is activated in the 1st and 3rd `free` cycles
	(see BPLHPTH,L) after horiz line start.It increments
	for the next line.