Changes
CRTC
,/* CRTC counter differences */
== CRTC counter differences ==
=== MA reload ===
On CRTC 1, at every raster line start of the first character line of the frame (ie. when VCC=0), MA is reloaded with R12/R13 instead of MA'. This discrepancy is a major source of incompatibility if the programmer does not take care. In demos and games, to be compatible with all CRTCs, program R12/R13 when VCC!=0. This will then take effect at the next frame start.
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=== MA buffering ===
At the end of the display of the last raster line of each character line (ie. when HCC=R1 and VLC=R9), MA' captures the current value of MA.
CRTC 2 is the exception, where MA' captures R12/R13 instead of MA at the last line of the frame.
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