Hello everybody. Long time listener, first time
caller :)
The stuff you see below is a snippet of my little
"Hello World" program based on Kirk Israel's 2600 101
lessons as well as Nick Bensema's How To Draw a
Playfield and Cycle Counting guide. I've put in what
I *think* the cycle counts are for this little snippet
of the code - could somebody just verify it for me so
I know if I'm on track or if I've missed something?
FYI: The number inside the [] is the current cycle,
the number outside is supposed to be how many cycles
the instruction will take (just like Nick's examples
in his guide).
Before I list the code I'd like to publicly say thanks
to *everybody* who makes it possible for guys like me
to get started in on this stuff. I definitely
appreciate how much time it must have taken you to
create this stuff, and it's been invaluable in getting
me this far (which isn't far at all but it's been a
blast of a trip).
Main
STA WSYNC
;Draw the playfield
TYA ;[ 0] 2
LSR ;[ 2] 2
LSR ;[ 4] 2
LSR ;[ 6] 2
TAX ;[ 8] 2
LDA PF0Data,X ;[10] 5
STA PF0 ;[15] 3
LDA PF1Data,X ;[18] 5
STA PF1 ;[23] 3
STA PF2 ;[26] 3
CheckActiveLander
CPY LanderYPos ;[29] 4
BNE SkipResetLander ;[33] 2 or 3
LDA LanderHeight ;[35] 4
STA LanderVisible ;[39] 4
SkipResetLander
LDX LanderVisible ;[36] or [43] 4
LDA LunarLanderData,X ;[40] or [48] 5
STA GRP0 ;[45] or [53] 3
CPX LunarLanderData ;[48] or [56] 4
BEQ SkipReduceLander ;[52] or [60] 2 or 3
DEC LanderVisible ;[54] or [62] 6
SkipReduceLander
DEY ;[60] or [68] OR [55]
or [63] 2
BNE Main ;[62] or [70] OR [57]
or [65] 3
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