NAME   rev ADDR type chip Description
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VHPOSR     006  R   A    Read vert and horiz position of beam, or lightpen
VHPOSW     02C  W   A    Write vert horiz position of beam, or lightpen
 BIT#  15  14  13  12  11  10  09  08     07  06  05  04  03  02  01  00
 USE   V7  V6  V5  V4  V3  V2  V1  V0     H8  H7  H6  H5  H4  H3  H2  H1

		RESOLUTION = 1/160 of SCREEN WITH ( 280 nS)