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Re: Video Coprocessor


On Mon, 10 Nov 1997, KC5TJA wrote:

> > Whenever the MP gets a chance -- at the end of the current memory
> > transaction of the stack processor (SP) -- it fetches the next video word
> > and puts it into PR.  In the case it is a jump, MP generates an immediate
> > second memory access go get the video word at the new location.  So, the
> > PR is sometimes filled with one memory access, sometimes with two. 
> 
> Does the video processor have a higher bus priority than the stack
> processor?  

Yes.  I think I've described how when exactly is the VP request serviced
by the MP.

> If not, then that would explain a large number of video
> effects, like jitter and spurious black lines and stuff 

There is one "video jitter" effect explained in my previous posting.

What is a "spurious black line" I have no idea, but I belive that this
might happen.

> (the old TRS-80s
> had this problem).

I'm quite sure the old TSR-80s does not use MuP21 :-)

Cheers,

--
Penio Penev <Penev@pisa.Rockefeller.edu> 1-212-327-7423