Kirk wr0te:
> LDA p0score ;accumulator = score
> ROL ;accumulator = score * 2
> ROL ;accumulator = score * 4
> CLC
> ADC p0score ;accumulator = (score * 4) + score = score * 5
> CLC
> ADC Score0Graphic
> STA GRP0
I think you're trying to do something like this:
(warning: untested code)
LDA p0score ;accumulator = score
ROL ;accumulator = score * 2
ROL ;accumulator = score * 4
ADC p0score ;accumulator = (score * 4) + score = score * 5
TAY
LDA Score0Graphic,y
STA GRP0
You want to create an offset but you're loading from an absolute address. What you want to do is:
GRPO=*(p0score*5 + Score0Graphic)
But what you're really doing in your version is:
GRPO=p0score*5 + *Score0Graphic
(I'm using * to indicate a pointer as in C)
This kind of thing is what the X and Y registers are there for, later CPU's allow you to do things more closely resembling true pointers like LDA [Pointer] but the 6502 is more limited (The only such instruction we have is JMP [Pointer])
You also shouldn't need the various CLC's given that the state of the carry should always be clear. In the first case, you ROL will clear the carry (ROLing 9 twice will never produce a carry) and the ADC p0score will also never produce a carry (9*4+9 is your max value)
>* what emulator supports showing the scan line count? how do you do it?
Z26 using the -v9 command line switch.
>* how can I find out how much of the 4K I'm actually using?
When assembling (with DASM) use the -l<filename> switch to generate a list file, then check that file.
Chris...
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