Assembler help for my X16-HELP.

[rje 163]

So I wrote a proof-of-concept "help" program, and at some point things just get confused.  It just cats text to the screen... what could possibly go wrong??

I figure I'm too close to the code, PLUS there's something subtle about assembly language that trips up my newbie asm mind.

 

I've abbreviated the data section, because, you know.

 

;
; cl65 -o help.prg -t cx16 -C cx16-asm.cfg help.s
;
chrout          = $ffd2
;       .segment "STARTUP"
;       .segment "INIT"
;       .segment "ONCE"
;       .segment "CODE"
                .org    $8000
                .export LOADADDR = *
	Main:   ldx #0
        lda curpos
	loop:   jsr $ffd2
        inc curpos
        lda curpos
        cmp #0
        beq newline
        cmp #42         ; '*' = EOF
        bne loop        ; no
        rts
	newline:
        lda #13
        jmp loop
	curpos:
	text:
        .asciiz "abs(n)"
        .asciiz "and; boolean or bitwise"
        .asciiz "asc(c$); petscii value"
        .asciiz "*** end of file ***"
	

Edited November 9, 2020 by rje

[JimmyDansbo 75]

curpos is a label, can you increment a label?

 

Edited November 9, 2020 by JimmyDansbo

[Stefan 63]

You can increase a label. Without testing the code, I think it in this case will increase the value of the first char in the first string. Not what rje intended.

You need to use an index. Assuming that the strings do not fit within 256 bytes you could use indirect indexed addressing mode, for example:

lda #<text
sta $30
lda #>text
sta $31
ldy #0

loop: lda ($30),y
cmp #'*'
beq eof
jsr $ffd2
iny
bne loop
inc $31
jmp loop

eof: rts

Edited November 9, 2020 by Stefan

[rje 163]

Yes, I should be indexing!  Thank you Stefan.