I'm going through the source for Fort Apocalypse and right off the bat I'm in need of some clarification.
LDA #%00111110 STA SDMCTL
Looking into applying values to SDMCRL, it seems that the value applied doesn't seem to make sense. Mapping the Atari is also throwing me off a bit (rim shot), and by that I mean this bit column. I would expect if you want something set, you just set the bit in that column.
AtariSDMCRL.png 12.28KB 10 downloads
Now, I would expect for the first four values you can only have ONE option set. So, if I want a wide playfield then I need to inject the decimal 3 into that address. The default value I see used in lot of the examples uses $22 (00100010). In this case, this seems like this sets it to Standard Playfield & Enable instructions to fetch DMA.
Could someone please clarify this better for me?