When R0=1:
* VLC Management: VLC increments and R9 updates are considered once per line (when HCC=0).
* Vertical Adjustment: If both VLC=R9 and VCC=R4 are true while HCC is 0 or 1 and R0=1, vertical adjustment starts. It ends when VLC, calculated for the next line, equals R5.
* Register Update: R4, R5, and R9 updates are considered only when HCC=0. R8 is evaluated at each HCC=0.