Date   : Thu, 05 Mar 2009 09:48:45 +1100
From   : richard@... (Richard Wilson)
Subject: Fwd: New Screen Modes with ARM7 Co-Processor?

 

> -----Original Message-----
> From: John Kortink
> Sent: Wednesday, 4 March 2009 10:54 PM
> To: bbc-micro@...
> Subject: Re: [BBC-Micro] Fwd: New Screen Modes with ARM7 Co-Processor?
> 
> >I would think that determining which field Odd or Even would 
> be relatively
> >easy since the VSYNC is delayed by (R0 + 1) / 2 on the odd 
> frames only. It's
> >a relatively simple task to measure the distance between 
> VSYNC pulses in a
> >frame by reading CA1 on the System VIA.
> 
> That's not how it works.
> 
> The length of the vsync and display periods are always
> exactly the same.

Perhaps you should actually write some code to test this, instead of just
assuming the 6845 was designed to work exactly like an interlaced TV/Video
signal, and telling me (and Tommo) that we are wrong when we both have more
knowledge of the 6845 than you do.

Richard