Posted By
Csabo
on 2024-11-09
18:37:06
|  Re: Building the Giana Sisters Sources
Delay (done quick-and-dirty), to get the horizontal raster positioning within the IRQ just right. ASL $#### takes 6 cycles, which is the second longest "pause" you can do (7 is the most cycles). The address does not matter, but $FF3F is a safe memory location, no side effects (other than the RAM continues to be paged in, but we'd want that anyway). You can see the last one being commented out, that was "too much" 
In other words, it doesn't matter what the CPU does there as long as it does something (and doesn't mess up the 3 pre-loaded values in A, X and Y). Placing 3 NOPs in place of one ASL would do the exact same thing as well (since one NOP is 2 cycles). |
