*** name 'demo1.txt - a simple demonstration of 6809+apple'
 title '(c) 1981, conejo computer products'

 page

* file=demo1.txt
* 6809 / apple demo prog
* runs a counter on top line
*** opt num
 org 4096 ; <<< change as desired <<<
screen equ $7f0 ; crt address
beep equ $c030 ; i/o for speaker
start bra begin
adr fdb $628 ; screen addr

begin leas endp+232,pc ; set stack pointer
 ldx adr,pc ; screen address
 leay msg1,pc ; "6809 COUNTING ...."
l100 lda ,y+
 sta ,x+
 bne l100

l200 ldb #'0' ; ASCII ZERO
 leay msg1a,pc ; buffer address
 inc 6,y ; from here we increment bcd digits
 lda 6,y ; by adding 1 til '9' then do carry
 cmpa #'9'
 bls l300
 stb 6,y
 inc 5,y
 lda 5,y
 cmpa #'9'
 bls l300
 stb 5,y
 inc 4,y
 lda 4,y
 cmpa #'9'
 bls l300
 stb 4,y
 tst beep ; click speaker
 inc 3,y
 lda 3,y
 cmpa #'9'
 bls l300
 stb 3,y
 inc 2,y
 lda 2,y
 cmpa #'9'
 bls l300
 stb 2,y
 inc 1,y
 lda 1,y
 cmpa #'9'
* inc a
;start lda *
; bra start
 bls l300
 stb 1,y
 inc ,y
 lda ,y
 cmpa #'9'
 bls l300
 stb ,y

l300 leax msg1,pc ; send data to crt
 ldy adr,pc
l400 lda ,x+ ; move local to crt memory
 sta ,y+
 bne l400
 bra l200 ; main loop

msg1 fcc "6809 COUNTING "
msg1a db "0000000",0
cnt equ msg1a-msg1
endp equ *

 end start