Re: C65 on Ebay

From: Mia Magnusson <mia_at_plea.se>
Date: Mon, 6 Nov 2017 16:54:54 +0100
Message-ID: <20171106165454.00006a95@plea.se>
Den Sun, 5 Nov 2017 20:42:44 +0100 skrev silverdr@wfmh.org.pl:
> 
> > On 2017-11-05, at 20:31, Mia Magnusson <mia@plea.se> wrote:
> > 
> >>> Well, you can use a PLL for the system clock oscillator and
> >>> control the PLL so sync *outputs* from the Amiga is in phase with
> >>> sync from the signal you genlock onto.
> >> 
> >> Theoretically looks like you could probably do this (and then
> >> constantly monitor for drifting and react), but the questions are:
> >> 
> >> 1) why make it more difficult and expensive while at the same time
> >> potentially less reliable and slower to lock?
> > 
> > If you only feed h+v-sync into the computer but let the computer run
> > the pixel clock of it's internal oscillator then you will have
> > jitter of atleast one 28MHz clock cycle.
> 
> Now it's me "?" ...

Which part is hard to understand?

> >> 2) what for - if there is nobody willing to listen to those sync
> >> pulses anyway?
> > 
> > ?
> 
> You wanted to sync the output pulses from the computer. The question
> is what would you use those for if nobody is willing to listen to
> them. The whole "house" listens to "house sync", not to what one of
> the slave appliances in the house is trying to say.
 
A PLL is used to control a 28MHz VCO feeding the 28MHz input so the
outputed h+v-sync from the computer is in sync with the "house sync".

This is the only way to generate a jitter free genlocked picture.

Of course the computer would sync faster if you also feed it h+v-sync,
but that isn't strictly necessary as you anyway need to feed 28MHz.


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Received on 2017-11-06 17:02:12

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