Subject: Re: [stella] single digit scoring... From: Christopher Tumber <christophertumber@xxxxxxxxxx> Date: Sun, 24 Aug 2003 20:18:55 -0400 |
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... ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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