Hi Ben!
>OK, actually I sat down and thought it out, and I
>suppose it wouldn't be as hard as I originally
>thought...basically just treat the whole 40 column
>playfield as a giant register and just do ROLs and
>RORs to get the masking bit where I want it. The fact
>that the PF0 bits are packed into one byte will be a
>minor inconvenience, but shouldn't be anything too
>bad...
>
>I suppose I will try to implement this strategy first
>for the playfield drawing routine, since that's a big
>ROM hog right now...
I used a simple ANDing table to do it:
disintigratetab
.byte %01111111
.byte %10111111
.byte %11011111
.byte %11101111
.byte %11110111
.byte %11111011
.byte %11111101
.byte %11111110
If you are on a reflected byte, you can EOR #$07 the
index, so the same table always does the job.
Of course, RORing and ROLing the complete thing back and
forth, plus a CLC inbetween can result in a very clever
solution, too. Cycle consuming, but ROM saving.
Greetings,
Manuel
----------------------------------------------------------------------------------------------
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
