Hi,
The overscan trick was, I think, first discovered by NOP and used in
"Unknown Reality" at the title screen. Achieving the vertical overscan
on the V9938/V9958 is actually quite simple. You only need two line
interrupts (using r#19) and flip the LN bit (r#9 b7). The LN bit selects
between a screen height of 192 lines and 212 lines.
The first line interrupt needs to be at a line before line 192 and it
should set the LN bit (screen height = 212 lines). The second line
interrupt should be at a line beyond line 212 and clear the LN bit
(screen height = 192 lines). This will somehow 'confuse' the VDP and it
will keep on displaying skipping the black border in Y-direction
alltogether.
Bye, /\/\ark
****
MSX Mailinglist. To unsubscribe, send an email to [EMAIL PROTECTED] and put
in the body (not subject) "unsubscribe msx [EMAIL PROTECTED]" (without the
quotes :-) Problems? contact [EMAIL PROTECTED] (www.stack.nl/~wiebe/mailinglist/)
****
