Sorry for the multiple questions but I want to understand how these
illegal opcodes work as I think they may help me...
Thomas, I'm looking at the kernel you did for Glenn for Death Race and I
have a question. In this code snippet...
; draw car #0:
lda #CARHEIGHT-1 ; 2
dcp P0_Y ; 5
bcs .doDraw0 ; 2³
lda #0 ; 2
.byte $2c ;-1
.doDraw0:
lda (P0_Ptr),y ; 5
sta GRP0 ; 3 = 18 @20
I see you are using dcp (opcode $c7, decrement and compare). What does
this have to do with the y-register? You're not updating y for each
scanline, right? Does dcp effect the y-register is some way? I had this
question back when you posted skipDraw
(http://www.biglist.com/lists/stella/archives/200102/msg00282.html) but
I never asked :) Apparently, I'm the only one here that doesn't get it
:(
Take care,
Dennis
----------------------------------------------------------------------------------------------
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
