NAME rev ADDR type chip Description --------------------------------------------------------------------------- VSSTOP H 1CA W A Vert position for VSYNC start VTOTAL H 1C8 W A Highest numbered vertival line (VARBEAMEN = 1) It`s the line number to reset the counter, so there`s this many + 1 in a field. The exception is if the LACE bit is set (BPLCON0), in which case every other field is this many + 2 and the short field is this many + 1.