Jorge ChB wrote:
Michael J. Mahon <mjmahon@aol.com> wrote:mdj wrote:I would suspect that the TEXT/GRAPHICS softswitch triggers it.Correct, and the TEXT softswitch is off in MIXED/GRAPHICS mode.It's possible in this case that the killer doesn't activate until a video cycle ends or starts.Well, if, as you say, the Color Burst is being gated in by the TEXT softswitch then certainly it's going to be toggled on and off by this :LOOP: LDA TEXTMODE WAIT (A FEW TENTHS OF A FRAME) LDA GRAPHICSMODE WAIT (A FEW TENTHS OF A FRAME) JMP LOOPI'd suspect that the colour burst being absent in the middle of a frame would produce pretty bizzarre results.Like for example ? I ran the program above and nothing "bizarre" came on the screen.
I didn't say something bizarre *would* happen, only that it *could* happen, because it is completely outside the NTSC specification. Most analog monitors will probably ignore short-duration changes in burst status, in either direction, but this is not a specified behavior. And the color reference oscillator is free-running during the absence of the burst. I expect that many digital monitors will react much more quickly to burst changes, but it may still take a few lines, and results will not be consistent across monitors. It's undefined behavior. -michael Parallel computing for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."