page	60,132
				title	SWAPLPTS - Swap LPT1 and LPT2
; 
; S W A P L P T S . A S M
;
; Copyright(C) 1991 John W Grothman.  All rights reserved.
;
; Released to the public domain.
;
; purpose:
;	Swap LPT1 and LPT2.
;
; to do:
;
; technical notes:
;	This is a SIMPLE thing to do.  Just swap the base I/O addresses
;	in low DOS memory that DOS uses to map the LPT port hardware.
;
; modification log:
; 1.0		4/12/90 	John W Grothman (CompuServe 73740,1540)

cseg	segment para public 'code'
		assume	cs:cseg, ds:cseg, es:cseg, ss:cseg

		org 	100h

begin	proc near
		xor		ax, ax
		mov		ds, ax		; set DS to 0 (DOS low memory (data) area)
		mov		bx, 0408h	; low DOS memory offset of LPT1 base I/O address
		mov		ax, [bx]	; get it and
		mov		dx, ax		;	save in DX
		mov		bx, 040ah	; low DOS memory offset of LPT2 base I/O address
		mov		ax, [bx]	; get it and
		mov		cx, ax		;	save in CX
		mov		ax, dx		; get back LPT1
		mov		[bx], ax	; and put it in LPT2
		mov		bx, 0408h	; address of LPT1 base I/O address
		mov		ax, cx		; get back LPT2
		mov		[bx], ax	; and put it in LPT1

		mov 	ax, 4c00h	; terminate with ERRORLEVEL = 0
		int 	21h
		ret
begin	endp
cseg	ends
		end 	begin