About VDP command operation code = 0

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By Hrothgar

Champion (479)

Аватар пользователя Hrothgar

21-06-2011, 16:44

But the single large fullscreen copy was ruled out already due to the corruption issues, so my question stands what a command-complete interrupt would solve in practice? The time between two 16×16 copies seems too small to do anything with the CPU apart from preparing the next copy, and continuously polling the status hardly causes overhead and waiting time.

By PingPong

Prophet (4093)

Аватар пользователя PingPong

21-06-2011, 21:54

@mth: unfortunately changing r18 during vblank time gives us corruption. that's exactly what my test program do.
@horthgar: the time for a logical 16x16 copy is long enough to waste z80 time.
time ago i've realized a tilebased scroller in sc5 with differential tile copy. the routine worked by issuing multiple 8x8 copy commands, in high speed. Even in the worst case, the z80 had to wait between two consecutive tile copy operations.

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