;
;	Test program 1
;	31V4 Assignment 2
;	Written by : D Budgeb
;	On : 9 March 1989
;
;	This program is largely nonsense code but it does
;	perform some of the actions of a routine that controls
;	a simple device using program controlled output.
;
srce1=4000
dest1=4002
carry=177502
;
.start 1000
;
init:	mov #2000,r0	; set up buffer
	mov #10,r1	; and character count
	jsr pc, print	; call print routine
	mov #21,@#srce1	; copy data
	mov r2 ,@#dest1	; and again - note additional spaces
	mov r3, -(sp)	; push register 3 on to stack
	clr @#carry
	jsr pc,addsub	; call addsub
	tst (sp)+	; clear the stack - result unimportant
	rts pc		; return control to caller
;
;	subroutine print
;
print:	movb (r0)+ , -(sp)	; pop and push
	dec r1
	jsr pc, writec		; call character writing routine
	cmp r1,#0		; have we reached the end?
	bgt print		; skip back if not
	rts pc			; else return
;
;	subroutine writec - transfer one byte (character)
;
writec: tstb status		; is device ready
	bgt writec		; loop back if not
	movb (sp)+, buffer	; copy character from stack
	rts pc			; and return
;
; subroutine addsub
;
addsub: add @#srce1, @#dest1	; add contents of two locations
	rts pc			; and return
;
;	allocate store space by useless intructions
;
status: tst r0			; reserve one word
buffer: tst r0			; reserve another
;
.end