Based on your BASIC program (and provided that I read it right) I would guess the assembler version should go something like this (saving a few cycles here and there):
ldx #1
ldy #0
sty $80 ; our "a", just a random spot in the ZP
stx $dd03
loop:
sty $dd01
stx $dd01
inc $80
jmp loop
This would naturally loop forever and won't do much as-is. You also need a timer and a print function. Let me know if you need more help and I'll be glad to assist.
