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skilldrick
define instruction from easy 6502 not working
Which assembler are you trying to use? Each assembler does have unique choices for how to express a program, and easy6502 is no exception!
I tried downloading the 6502 JS Assembler, it would not recognize the Define instruction as used in the tutorials.
On Wed, Nov 22, 2017 at 8:12 AM, BigEd [email protected] wrote:
Which assembler are you trying to use? Each assembler does have unique choices for how to express a program, and easy6502 is no exception!
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Do you mean http://www.6502asm.com/ ? If so, it has no define, so from the examples we see the tactic is to use a label:
* = $hhhh
name
Oops sorry I have just realised that I was confused between easy6502 and 6502js. Let me look into this. We do know the two assemblers have diverged. My own fork of 6502js is different again.
OK Cool thank you, yeah I was hoping that there was one of these I could download to practice assembly on my own, like building snake from scratch with the embedded screen you guys had in easy 6502
if this is possible, plz lemme know, I know easy6502 had a define instruction for their snake example
On Sun, Nov 26, 2017 at 9:55 AM, BigEd [email protected] wrote:
Oops sorry I have just realised that I was confused between easy6502 and 6502js. Let me look into this. We do know the two assemblers have diverged. My own fork of 6502js is different again.
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for example, trying to use the easy 6502 assembler downloaded from easy 6502
in the tutorial, they use (define) as a means of declaring constants/variables. Upon downloading the Assembler though, the define instruction stops working. How would I still define variables/constants?
On Sun, Nov 26, 2017 at 4:11 PM, Raymond Liberto [email protected] wrote:
OK Cool thank you, yeah I was hoping that there was one of these I could download to practice assembly on my own, like building snake from scratch with the embedded screen you guys had in easy 6502
if this is possible, plz lemme know, I know easy6502 had a define instruction for their snake example
On Sun, Nov 26, 2017 at 9:55 AM, BigEd [email protected] wrote:
Oops sorry I have just realised that I was confused between easy6502 and 6502js. Let me look into this. We do know the two assemblers have diverged. My own fork of 6502js is different again.
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Just started looking at this. I see you can use the same kind of workaround, abusing the label mechanism to define a symbol:
* = 255
mask:
* = $600
start:
nop
lda mask
nop
How would you use this technique in something like a constant? Lets say for example I wanted to set sysRandom = $fe (the RNG on the mock 6502)
*=255 - is this setting mask to 255 decimal? I'm a little confused as to how this example works in practice, thanks for the help
On Mon, Nov 27, 2017 at 1:01 PM, BigEd [email protected] wrote:
Just started looking at this. I see you can use the same kind of workaround, abusing the label mechanism to define a symbol:
= 255 mask:
= $600 start: nop lda mask nop
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Here's a slight expansion of the example:
* = 127
mask:
* = $fe
sysRandom:
* = $600
start:
nop
lda mask
and sysRandom
nop
and the disassembler says we got this:
Address Hexdump Dissassembly
-------------------------------
$0600 ea NOP
$0601 a5 7f LDA $7f
$0603 25 fe AND $fe
$0605 ea NOP
So, it's a little ugly, and it takes two lines to make each define, but I think it works generally.
(However, I notice the tactic fails for immediate values. I should have written
lda #mask
but that turns out not to work at all.)
Aghh that's unfortunate, was going to use this idea for costants related to collision, if there's a workaround, kindly let me know, thx!
On Nov 27, 2017 13:33, "BigEd" [email protected] wrote:
(However, I notice the tactic fails for immediate values. I should have written lda #mask but that turns out not to work at all.)
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oh and just for context, I'm trying to build snake/pong in the assembler without using the help of the tutorial, so i assume even if reformatted for the above hack, that code still wouldnt assemble given the #immediatevalue error.
On Mon, Nov 27, 2017 at 1:35 PM, Raymond Liberto [email protected] wrote:
Aghh that's unfortunate, was going to use this idea for costants related to collision, if there's a workaround, kindly let me know, thx!
On Nov 27, 2017 13:33, "BigEd" [email protected] wrote:
(However, I notice the tactic fails for immediate values. I should have written lda #mask but that turns out not to work at all.)
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I think we'd need to bring the whole 'define' mechanism in from easy6502 to 6502js.
Meantime, could you work using a local copy of easy6502 instead of using 6502js? I tend to try out small snippets just using the first emulation window - the snake is way down the file and needn't distract you.
Yes that would be perfect, could you link me to the appropriate place to grab the easy 6502 engine? Tha k you so much
On Nov 27, 2017 13:57, "BigEd" [email protected] wrote:
I think we'd need to bring the whole 'define' mechanism in from easy6502 to 6502js.
Meantime, could you work using a local copy of easy6502 instead of using 6502js? I tend to try out small snippets just using the first emulation window - the snake is way down the file and needn't distract you.
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Oh wait I see what you mean, yeah that sounds good, please keep me posted as to when you add in define. Also curious, how do I reserve bytes for variables? For the nes, all I usually will do is (nesasm)
ballspeedx: .rs 1
On Nov 27, 2017 13:57, "BigEd" [email protected] wrote:
I think we'd need to bring the whole 'define' mechanism in from easy6502 to 6502js.
Meantime, could you work using a local copy of easy6502 instead of using 6502js? I tend to try out small snippets just using the first emulation window - the snake is way down the file and needn't distract you.
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Reserving some bytes... I think the effect will be to set the label and then for the next label to take a slightly higher value. So perhaps just use dummy code sequences instead:
* = $80
onebyte:
nop
twobytes:
nop
nop
twomorebytes:
lda 0
eightbytes:
jmp dummy
jmp dummy
lda 0
I made a fork of the emulator here and fixed the issue partially. the following would now work :
define white $01
define topleft $0200
lda #white
sta topleft
I haven't yet managed to make it work in indexing modes though, so
sta $0200,#value
would not assemble, assuming value is a constant defined by the define keyword
