I'm trying to understand how the video hardware (CRTC and Gate Array) in Amstrad CPCs works. Specifically, I have a question about the behavior of the refresh memory addresses and row adresses output by the Motorola 6845 CRT controller during horizontal/vertical retrace.
When the horizontal counter reaches the value "Horizontal Displayed" (register 1) is the refresh memory address reset to the start of the current/next character row immediately?
I'm confused, because I read in the Datasheet for the CRTC:
Both the memory addresses and the row addresses continue to run during vertical retrace thus allowing the CRTC to provide the refresh addresses required to refresh dynamic RAMs.
I guess that would make sense for vertical retrace because the refresh memory address is reset to the value of "Display Start Address" (register 12/13) at the start of the frame anyways.
But I'm unsure what happens during horizontal retrace.
So, in other words what values do the refresh memory addresses and the row addresses have during horizontal and vertical retrace?