;                                           page 60,132
;                                           title SWAPLPTS - Swap LPT1 and LPT2
; 
; S W A P L P T S . A 8 6
;
; Copyright (C) 1991 John W Grothman.  All rights reserved.
; Released to the public domain.
;
; purpose:
;   Swaps LPT1 and LPT2.
;
; 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              4/12/91        John W Grothman (CompuServe: 73740,1540)
; Original version in proprietary assembly language.
;
; 1.1              8/14/94        Kirk Lawrence
; Added screen message, so user can tell that something has actually happened.
; Translated the source code from proprietary to generic assembly language,
; so that it will compile under shareware-type compilers.
;
; 11-11-98
; Ported to CP/M-86 by Kirk Lawrence.
;
        cseg                    ;start of code segment
        org     100h            ;leave room for base page
        jmp     start
;
msg     db      10,13,' SWAPLPTS Version 1.1 - Printer Port Swapper'
        db      10,13,' Copyright 1991 by John W Grothman.  All rights '
        db      'reserved.'
        db      10,13,' Released to the public domain.',10,13
        db      10,13,' => LPT1 and LPT2 have been swapped.',10,13,07,'$'
;
start:
        mov     cl, 9           ;function 9 - print string
        mov     dx, offset msg  ;point DX to screen message
        int     224             ;call BDOS
        xor     ax, ax          ;zero out register AX
        mov     ds, ax          ;set DS to 0 (low memory (data) area)
        mov     bx, 0408h       ;low memory offset of LPT1 base I/O address
        mov     ax, [bx]        ;get it and
        mov     dx, ax          ; ...save in DX
        mov     bx, 040Ah       ;low 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
        xor     cx,cx           ;function 0 - reset system
        int     224             ;call BDOS
end