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'Composite video signal (50Hz, 625 lines)'
1998\01\02@100603 by Rickard Gunie

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I'm trying to generate a video signal using a PIC16F84 running at 12MHz,
but i have some trouble with the frame-synchronization. (The picture is
not stable) Could someone explain how the frame-sync works ?

1998\01\02@113122 by jrmont

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Rickard Gunie wrote:
>
> I'm trying to generate a video signal using a PIC16F84 running at 12MHz,
> but i have some trouble with the frame-synchronization. (The picture is
> not stable) Could someone explain how the frame-sync works ?

Rickard,

You have not described enough about the signals that you are already
generating, but I am going to take a guess that you are not producing
the equilizing pulses that are needed before and after the vertical sync
pulse. These occur at 1/2 the horizontal period. The timing is too
difficult to explain in text. I suggest that you take a look at one of
the many books on the subject. If you have questions then, I would be
glad to help you.

Also, if you are not tied to using a PIC for this application, you might
consider a chip that Philips called "MTV". As I recall, it is an 8051
core with a video generator built in. Good Luck.

1998\01\02@213855 by Jim Main

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In article <spam_OUT34AD32FA.204ATakeThisOuTspamiquest.net>, John Montalbano
<.....jrmontKILLspamspam@spam@IQUEST.NET> writes
>Rickard Gunie wrote:
>>
>> I'm trying to generate a video signal using a PIC16F84 running at 12MHz,
>> but i have some trouble with the frame-synchronization. (The picture is
>> not stable) Could someone explain how the frame-sync works ?
>
>Rickard,
>
>You have not described enough about the signals that you are already
>generating, but I am going to take a guess that you are not producing
>the equilizing pulses that are needed before and after the vertical sync
>pulse. These occur at 1/2 the horizontal period. The timing is too
>difficult to explain in text. I suggest that you take a look at one of
>the many books on the subject. If you have questions then, I would be
>glad to help you.
>
>Also, if you are not tied to using a PIC for this application, you might
>consider a chip that Philips called "MTV". As I recall, it is an 8051
>core with a video generator built in. Good Luck.

Most modern tv's have no problem in coping with a vertical interval
devoid of equalising pulses - in fact many early videogame consoles
didn't output any (the Sinclair Spectrum for one)

So long as the field sync is present and correctly timed, the tv should
lock up to it.

Jim

--
Jim Main

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