Memory location for sinchronization

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jorodr
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Memory location for sinchronization

Post by jorodr »

Hallo :)
Me and my guys are working to connect Oric (Pravetz 8D) to CGA/EGA monitor. We have success with EGA but have difficults wit CGA. My question is:
Can someone tell me the memory location that rules 50Hz or 60Hz is sinchro-impulses. Thanks in advance,

George
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Dbug
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Post by Dbug »

There is no location.
The video chip does not have any register.

But you can change the frequency by having the video display read a byte of the screen that contains a "frequency change" attribute.

Your choice:

24,25 = TEXT 60hz
26,27 = TEXT 50hz
28,29 = HIRES 60hz
30,31 = HIRES 50hz

You can force to TEXT 60hz by doing that:
POKE #BFDF,24

You can force to HIRES 60hz by writing 28 or 29 instead of 24.
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