FRAME AND SCANLINE TIMING
VDG FRAME TIMING
| Area | Scanlines |
|---|---|
| Vertical Blanking | 13 |
| Top Border | 25 |
| Display | 192 |
| Bottom Border | 26 |
| Vertical Retrace | 6 |
COCO 1/2 NTSC SCANLINE TIMING
f = 315 MHz
14MHz clock frequency is 315 / 22 1) = 14.318181818181818 MHz
FAST RATE CLOCK DIVIDER 8
Crystal clock divided by SAM fast rate clock divider (/8):
315 / 22 / 8 = 1.7897727272727273 MHz
Scale up for clock ticks per second:
315 / 22 / 8 = 1.7897727272727273
Clock ticks per frame (both fields):
315 / 22 / 8 * 1000000 / 60 = 29829.545454545456
Clock ticks per scanline (262.5 scanlines per field):
315 / 22 / 8 * 1000000 / 60 / 262.5 = 113.63636363636364
NOTE: Running a CoCo 1/2 at SAM Fast rate will cause video and RAM corruption unless a SAM Accelerator is also installed.
SLOW RATE CLOCK DIVIDER 16
Crystal clock divided by SAM slow rate clock divider (/16):
315 / 22 / 16 = 0.8948863636363636 MHz
Scale up to clock ticks per second:
315 / 22 / 16 * 1000000 = 894886.3636363636
Clock ticks per frame (both fields):
315 / 22 / 16 * 1000000 / 60 = 14914.772727272728
Clock ticks per scan line (262.5 scanlines per field):
315 / 22 / 16 * 1000000 / 60 / 262.5 = 56.81818181818182
COCO3 SCANLINE TIMING
FAST RATE CLOCK DIVIDER 16
Crystal clock divided by GIME fast rate clock divider (/16):
28.636363636363637 / 16 = 1.7897727272727273 MHz
Scale up for clock ticks per second:
28.636363636363637 / 16 * 1000000 = 1789772.7272727273
Clock ticks per field:
28.636363636363637 / 16 * 1000000 / 60 = 29829.545454545456
Clock ticks per scanline:
28.636363636363637 / 16 * 1000000 / 60 / 262 = 113.85322692574601
SLOW RATE CLOCK DIVIDER 32
Crystal clock divided by GIME slow rate clock divider (/32):
28.636363636363637 / 32 = 0.8948863636363636 MHz
Scale up for clock ticks per second:
28.636363636363637 / 32 * 1000000 = 894886.3636363636
Clock ticks per field:
28.636363636363637 / 32 * 1000000 / 60 = 14914.772727272728
Clock ticks per scanline:
28.636363636363637 / 32 * 1000000 / 60 / 262 = 56.92661346287301
MC-10 SCANLINE TIMING
NTSC clock divided by 4: 3.578545 / 4 = 0.89488625 MHz
Scale up for clock ticks per second:
3.578545 / 4 * 1000000 = 894886.25
Clock ticks per field:
3.578545 / 4 * 1000000 / 60 = 14914.770833333334
Clock ticks per scanline:
3.578545 / 4 * 1000000 / 60 / 262 = 56.926606234096695
DRAGON PAL SCANLINE TIMING
4.43361875 MHz 625 scanlines
RTS
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