When R0=1 (2µs frames):
* VLC Management: VLC increments and R9 updates are considered only once per character line because HCC only reaches 1.
* Vertical Adjustment: If 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 a new line equals R5.
* Register Update: R4, R5, and R9 updates are considered only when HCC=0. R8 is evaluated at each HCC=0.