Russ Perry Jr wrote:
> But you're doing that AND a lot to mask the high 6 bits, so...
I'd just turn the shifting direction, then it's done with:
Preloading: x10x01x00 (The first X is the carry, so it doesn't matter,
too!)
lda FrameCounter
ror
ror
ror
sta FrameCounter
and #$03
tax ;(or tay whichever index you need)
Which is 10 bytes and 16 cycles I think.
But there's yet another (more hidden) advantage of the table: You don't
have to preload anything, when zeroing out the machine on startup
anyway.
But another brilliant thought, Russ! I love thinking about such
'alternate ways for standard probs' :-)
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Besides, as a summary I'd say:
For getting sequences of powers of two (0/1 v 0/1/2/3 v ...):
INC FrameCounter
LDA FrameCounter
AND $XX
TAX
For getting sequences of three different values (0/1/2):
LDY frameCounter
LDX framecountertab,Y
STX frameCounter
framecountertab
.byte $01,$02,$00
For getting sequences of other uneven values (0/1/2/3/4/5):
dec FrameCounter
bpl .skipReset
lda #MAXVAL
sta FrameCounter
.skipReset
ldx FrameCounter
Is there any more ideas for these problems?
Besides, I have an idea:
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Maybe we should somewhere gather such 'ASM methodism' results?
Brilliant thought: What if, when we have final consens about something
being the 'ultimate best' solution, post it under a Non-Discussion,
extra preserved topic?
Let's say, when nobody comes with a better solution to this prob until
monday, I'll revamp this topic with a little article and post it tagged
as
"[ASM WIZARDRY] #1 : Sequence Counting [Don't Reply!]". Now, it could be
very easy found in the archive, with a simple query for 'ASM WIZARDRY'.
One would get only the most useful results like this:
"[ASM WIZARDRY] #1 : Sequence Counting [Don't Reply!]"
"[ASM WIZARDRY] #2 : Cycle Optimizing [Don't Reply!]"
"[ASM WIZARDRY] #3 : RAM Optimizing [Don't Reply!]"
"[ASM WIZARDRY] #4 : ROM Optimizing [Don't Reply!]"
"[ASM WIZARDRY] #5 : Illegal Opcodes LAX [Don't Reply!]"
So, the general future way would be to write an article for building up
such an "methodism repository", review it under any name and when
approved by the whole list, post a tagged variant again.
I'd even suggest a second series for specific 2600 topics like:
"[2600 WIZARDRY] #1 : Horizontal positioning [Don't Reply!]"
"[2600 WIZARDRY] #2 : NTSC/PAL conversions [Don't Reply!]"
"[2600 WIZARDRY] #3 : Speeding up the kernal [Don't Reply!]"
I know, most of these articles are already written and hidden somewhere,
but what about dusting them of, revamping them and tag them for an easy
find?
Ok, there's one little drawback: When someone is pointing out to such an
article saying something like "Search in the archive for [ASM WIZARDRY]"
he would get all messages containing previous "Search in the archive for
[ASM WIZARDRY]" pointers, since the archive doesn't provide topic only
searches.
But in general, what about this idea? Good/bad? Go for it?
Greetings,
Manuel
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