Changes
CRTC
,/* UM6845R and R31 */
3. CRTC type 4 is the same as CRTC type 3. The registers also repeat as they do on the type 3.
== Horizontal and Vertical Sync (R3) ==
UM6845:
Bits 7..4 define Vertical Sync Width. If 0 is programmed this gives 16 lines of VSYNC.
Bits 3..0 define Horizontal Sync Width. If 0 is programmed no HSYNC is generated.
UM6845R:
Bits 7..4 are ignored. Vertical Sync is fixed at 16 lines.
Bits 3..0 define Horizontal Sync Width. If 0 is programmed no HSYNC is generated.
MC6845:
Bits 7..4 are ignored. Vertical Sync is fixed at 16 lines.
Bits 3..0 define Horizontal Sync Width. If 0 is programmed this gives a HSYNC width of 16.
Pre-ASIC/ASIC:
Bits 7..4 define Vertical Sync Width. If 0 is programmed this gives 16 lines of VSYNC.
Bits 3..0 define Horizontal Sync Width. If 0 is programmed this gives a HSYNC width of 16.
== UM6845R and R31 ==
