Date   : Mon, 29 Jan 1996 13:17:33 GMT
From   : lamcw <lamcw@...>
Subject: Re: Vertical blank interrupt

Tom Seddon <T.W.Seddon@...> wrote:

;I am aware that the vertical blank interrupt occurs 50 times a second, but
;I am unsure as to when it occurs. Does it occur when the visible display
;area -- that is, 256 scanlines or (display character rows)*(scan lines per
;character row) -- has all been traced, or does it occur when all 312
;scanlines (ie both visible and invisible) have been traced? Or is it
;rather more weird than this? 


I didn't find out either, so I guessed at the value by trial and error
until the Elite screen looked right :)

Chris Lam,
MacBeebEm Keeper.