Hi all,
I have been playing around with printing strings in 6502 in a C64 emulator with code like this:




and this works just nice and dandy

Now I want to try outputting some numbers (floating point) to debug floating point routines in my compiler.

This means I need to move a number to FAC1 (easy), convert it to ASCII string (easy), and then output the ASCII string pointed to by A/Y to the screen using $FFD2 (how?)



Any ideas?

Would I need to store A/Y in memory somwhere (zerpage?) and load A from there in a loop like I did in the first example from a label?

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

Your CMP #0 is redundant, because it is already done automatically as part of the LDA L1,Y. Since the INY will always give a non-0 result, you could save a byte by replacing the JMP L0 with BNE L0.

See my Tip of the Day #38 here about raising the level of the assembly language by using macros when possible. (I don't know if it's possible with the assembler you're using for the C64.) Your source code will become more concise and need less debugging to get it going, with no penalty in speed or memory in the 6502 computer you're going to run it on. The overhead is all borne by the assembler.



STR_ADR will have to be in zero page, but the string it points does not need to be.

Ok, thanks for that tip...I obviously didn't know that little gem



Nice tips Garth, cheers! Unfortunately the assember I am using win2c64 (http://www.aartbik.com/MISC/c64.html) doesn't currently support macros

Maybe I can add into my code generator a crude macro facility and do that part myself



STR_ADR will have to be in zero page, but the string it points does not need to be.[/quote]

Nice! Thanks mate

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

I think you want that

STX STR_ADR

to be

STY STR_ADR


Personally. I'd do it like this:



but that does assume that the string will never be more than 256 bytes

Woops, yeah, he did say A/Y, not A/X.

Thanks for the help so far guys

I have two questions though still:

1) I haven't had much luck in getting the ASCII value of the number to print out though...I am starting to think that it isn't a null-terminated string, but something else.

I don't suppose if any of you know the format of a FAC1 number converted to ASCII using the FOUT ($BDDD) C64 ROM routine?

I don't suppose it might have the string length first, then the string digits?

I haven't been able to find out anything online so far...

2) Has any of you had experience using an assembler called KickStart?

It seems pretty good, has a scripting language built into it, and also does macros

I am thinking of using it now in my project

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

It should return a null terminated string with the pointer to it in AY.

Lee.

Ok, then the only thing I can think of going wrong is that I am outputting the c64 floating point number (5-byte) in the wrong order then to the assembler...

I will have to try it the other way around, thanks

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

Shouldn't that be


Note the '#' signs for immediate addressing mode, so the low and high byte of the address L1 are loaded into A and Y respectively, not the values read from memory at adresses <L1 and >L2...

André

OMG! I didn't notice that foobar...D'OH!

I will fix that and try again

Thanks André...

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

It works!!! Yay!

This input:



Generated this assembler:



And this in turn ran on the C64 emulator and printed out the number I entered in the program

Thanks all!!

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

AAAHHHH!!! sometimes changing assemblers can be a real pain in the arse! LOL

I had this code which worked using win2c64:


but when I switched over to Kick Assembler and altered the code so it would compile like so:



outputting the code in the c64 emulator stopped working, ie printing out garbage + changing colours. I couldn't figure out why for days!!

I only discovered yesterday that with the Kick Assembler, I had to put the text to output in CAPITAL LETTERS to work!!



Damn that was annoying!

I hope this helps someone else

EDITED: removed the cmp #0 from the code...

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls

And again, for efficiency, remember you never need CMP #0 after an LDA. It's an implied automatic integral part of it. Same with ADC and others.

The reason has nothing to do with the assembler per se, and everything to do with PETSCII, Commodore's modified form of ASCII. HELLO WORLD in ASCII comes out as hello world in PETSCII on an assembler that is not CBM-specific. hello world in ASCII is not part of the PETSCII character set, and instead maps to PET graphics and control characters. win2c64 maps your text strings into PETSCII, so it seems to work right.

Also, as Garth previously noted, CMP #0 is unnecessary. The status register flags are automatically conditioned by load, arithmetic or logical operations (including R-M-W instructions). Hence the acting of loading a null into .A sets the .Z flag, causing the BEQ branch to succeed.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Sorry guys...I remember that little tidbit now...I just hadn't removed the cmp #0 from the code example My bad...I have removed it now



Thanks BigDumbDinosaur I guessed that might have been the reason after I got it working

I might look up the PETSCII codes and see if I can maybe convert upper-case chars to PETSCII shifted versions, and lowercase characters to normal upper-case characters as I am doing now

This could be handy if I want to do lower/upper-case characters in the other text mode on the C64...

Speaking of which, does any here know how to set the c64 text mode to upper-case only, or both lower/upper case?

cheers,
Paul

_________________
"The plastic veneer of civilization is easily melted in the heat of the moment" - Paul Nicholls