;
;	SumtreeC.asm
;
;  Program that implements a tree that sums integers
;
;  2-6-2008
;
; This program reads the number from the DOWN and RIGHT ports, adds them
; and sends the result to the UP port.
;
; Port0 (U)
; Port1 (L)
; Port2 (R)
; Port3 (D)
;

;Set-up reset vector
	ORG	00H
	LJMP	RESET

;---------------------------------------------------------------
	P0	EQU	80H
	P1	EQU	90H
	P2	EQU	0A0H
	P3	EQU	0B0H
	UP	EQU	80H
	LEFT	EQU	90H
	RIGHT	EQU	0A0H
	DOWN	EQU	0B0H

	ACC	EQU	0E0H
	B	EQU	0F0H

	SP	EQU	081H

;---------------------------------------------------------------
;	RAM MEMORY MAP
;
;	30h-4Fh	: spare
;
;	50h-FFh	: stack
;---------------------------------------------------------------
;
STACK	EQU	050h
;--------------------------------------------------------------
;Main program
	ORG	0100H


RESET:	
	MOV	SP,#STACK

	NOP
	NOP
	NOP
	NOP
	NOP

	MOV	A,DOWN		;read DOWN port
	MOV	B,A
	MOV	A,RIGHT		;read RIGHT port
	ADD	A,B
	MOV	UP,A			;Write UP port

HALT:
	SJMP	HALT

;--------------------------------------------------------------
END