## RE: [stella] Climber5 source and binary

 Subject: RE: [stella] Climber5 source and binary From: Thomas Jentzsch Date: Fri, 18 Apr 2003 16:47:09 +0200
```Dennis wrote:
>Would playerMotion here be the "delay" frames I have set up for the
>players (i.e. 4, 3, 2, and 1)?

No, playerMotion would contain "fractional delay frames".

Example: (SBC #\$60)
frame playerMotion	C
-	\$00			-
0	\$a0			0
1	\$40			1
2	\$e0			0
3	\$80			1
4	\$20			1
5	\$c0			0
6	\$60			1
7     \$00			1

The carry is clear in 3 out of 8 frames, so your resulting speed is
3/8 = (\$60/\$100). Fractional!
Other values: \$aa -> ~2/3, \$80 -> 1/2, \$55 -> ~1/3, \$40 = 1/4, ...
(but you can use *any* values you like here, e.g. \$ca -> ~0.79)

Note that playerMotion is only changed here and *not* reseted when
moving!

>As a matter of fact, where did you get the numbers for the first
>routine? Is there a formula you're using that I'm missing?

I think by now you should have got the answer already. Else it's my
fault and I should learn to explain myself better. ;-)

>you clear the carry bit instead of setting it so a bcc would move the
>player for the given frame.

I am using CLC to be able to subtract \$100 (by using \$ff) so that the
carry after the subtraction is always cleared and I get maximum speed
then (SBC M: A = A - M - 1 + C). Therefore I am reducing all subtract
values by 1.

BTW: You can use ADC (and SEC) instead. That's maybe a bit easier to
understand.

>\$04 - \$3F = \$C5 -> carry set, right?
>\$C5 - \$3F = \$86 -> carry cleared???

No, it's exactly the other way around. The carry is cleared when the
subtraction "crosses" 0.

>My only question for this is where do you come up with the number 30?
>I understand you get 36 from 30*6/5.

Why 30? Hm, it's 5*6. :-)

But you can use any higher value here as long as the results don't get
larger than \$ff. And the conversion to PAL works best when it can be
divided by 5.

Have fun!
Thomas

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