;
; COMOFF.A86 - Version 0.3
; Take All UARTs Off The Interrupt Bus
; Freeware from Kirk Lawrence
; (Inspired by the DOS freeware source code RS232OFF.C by Jim Michener)
;
;
        cseg                            ;start of code segment
        org     100h                    ;leave room for base page
        jmp     start                   ;get to the good stuff
;
nbr     dw      0                       ;timer storage variable
msg     db      13,10,'  COMOFF Version 0.3 - Take All UARTs Off The '
        db      'Interrupt Bus'
        db      13,10,'  Freeware from Kirk Lawrence',13,10
        db      13,10,'     Working$'
done    db      13,'    All COM ports have been "put to sleep."',13,10,'$'
;
timer:                                  ;timer routine for delays
        xor     ax,ax                   ;zero the AX register
        xor     cx,cx                   ;zero the CX register
        xor     dx,dx                   ;zero the DX register
        mov     ah,00                   ;function 0 - read system timer
        int     1Ah                     ;call BIOS timer services
        add     dx,3                    ;add our delay factor
        mov     nbr,dx                  ;store the result in variable
count:
        mov     ah,00h                  ;function 0 - read system timer
        int     1Ah                     ;call BIOS timer services
        cmp     dx,nbr                  ;has time period elapsed?
        jne     count                   ;no, go count some more
        mov     nbr,0                   ;zero the storage variable
        xor     ax,ax                   ;zero the AX register
        mov     cl,2                    ;function 2 - console out
        mov     dl,'.'                  ;print 'period' character
        int     224                     ;call BDOS
        ret                             ;return
start:
        mov     cl,9                    ;function 9 - print string
        mov     dx,offset msg           ;point to header message
        int     224                     ;call BDOS
;put COM1 to sleep
        mov     al,0
        mov     dx,03F9h
        out     dx,al
        call    timer
        mov     al,0
        mov     dx,03E9h
        out     dx,al
        call    timer
;put COM2 to sleep
        mov     al,0
        mov     dx,02F9h
        out     dx,al
        call    timer
        mov     al,0
        mov     dx,02E9h
        out     dx,al
        call    timer
;put COM3 to sleep
        mov     al,0
        mov     dx,03FCh
        out     dx,al
        call    timer
        mov     al,0
        mov     dx,03ECh
        out     dx,al
        call    timer
;put COM4 to sleep
        mov     al,0
        mov     dx,02FCh
        out     dx,al
        call    timer
        mov     al,0
        mov     dx,02ECh
        out     dx,al
        call    timer
;
        mov     cl,9                    ;function 9 - print string
        mov     dx,offset done          ;point to 'done' message
        int     224                     ;call BDOS
        xor     cx,cx                   ;function 0 - reset system
        int     224                     ;call BDOS
end