;Sven Eisenhauer
;MPS1 Versuch 3 Aufgabe 3
;16.06.2005

LSTOUT-
$SFR80515.INC
LSTOUT+

		ORG 0000h

		MOV DPTR,#0F803h
		MOV A,#92h
		MOVX @DPTR,A
		MOV P5,#0FFh
		MOV P4,#0FFh
		MOV P1,#0FFh
		MOV DPTR,#0F800h
		MOV A,#00h
		MOVX @DPTR,A
		INC DPTR
		MOVX @DPTR,A
		INC DPTR
		MOVX @DPTR,A
		MOV R0,#0
		MOV R1,#0
		MOV R2,#0
		MOV R3,#0

BEGIN:  JB P3.3,START
		LJMP 8000h
START:  LCALL EINLES

		JNB P3.2,SUBJMP
		LCALL ADDIT
SUBJMP: LCALL SUBST
		SJMP BEGIN

SUBST:  CLR C
		CLR OV
		CLR P3.4
		CLR P3.5
		MOV A,R0
		SUBB A,R2
		MOV R4,A ;LOWBYTE
		MOV A,R1
		SUBB A,R3
		MOV R5,A ;HIGHBYTE
		LCALL AUSG
		RET

ADDIT:  CLR C
		CLR OV
		CLR P3.4
		CLR P3.5
		MOV A,R0
		ADD A,R2
		MOV R4,A ;LOWBYTE
		MOV A,R3
		ADDC A,R1
		MOV R5,A ;HIGHBYTE
		LCALL AUSG
		RET

AUSG:	MOV P1,R4 ;LOWBYTE
		MOV A,R5
		MOV DPTR,#0F802h
		MOVX @DPTR,A  ;HIGHBYTE
		MOV P3.4,C
		JNB OV,NOOV
		SETB P3.5
		JB ACC.7,POS
		MOV A,#08h ;Backspace
		LCALL SENDSE
		MOV A,#2Bh ;+
		LCALL SENDSE
		RET
POS:    MOV A,#08h ;Backspace
		LCALL SENDSE
		MOV A,#2Dh ;-
		LCALL SENDSE
		RET
NOOV:   CLR P3.5
		MOV A,#08h ;Backspace
		LCALL SENDSE
		MOV A,#20h ;space
		LCALL SENDSE
		RET


EINLES: MOV DPTR,#0F800h ;Port A
		MOVX A,@DPTR
		MOV R1,A
		MOV R0,P1
		MOV DPTR,#0F801h ;Port B
		MOVX A,@DPTR
		MOV R3,A
		MOV R2,P4
		RET

SENDSE: MOV SBUF,A
		CLR TI
WARTE:  JNB TI, WARTE
		RET

END