Date   : Mon, 23 Jan 1995 10:18:21 -0600
From   : barnett@... (David Barnett)
Subject: Re: Scrolling Swapping

David Gilbert wrote:
>
>That is what I do - the scanline timing is calculated directly from the
>horizontal timing registers.  The vertical timing is also calculated that
>way - without
>any bodging the timing in the high res modes comes out at exactly the time for
>312 scanlines per field.
>
As a point of information.  If interlace is on (Depending on TV setting)
then it is 312.5 scan lines per field.

Each PAL line takes 64us (line to line time) but the BBC screen uses just
40us in the middle of each line - the rest is black + TV horizontal sync.

David Barnett