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TITLE  My_Int60.ASM
;===== Rutinen f”r 'CLS' placeras som en minnesresident rutin
;===== som kan anropas fr†n godtyckligt program med INT 60h
;---------------------------------------------------------------------
        INCLUDE TSR.MAC
;---------------------------------------------------------------------

CSEG    SEGMENT
        ASSUME CS:CSEG,DS:CSEG
        ORG 100H

Start:  jmp Install_TSR

;================================
Org_Rutin DD ?
;================================
;-------------------------------------------------------------------

Start_TSR:                              ;H„r startar den programkod som
                                        ;kommer att bli minnesresident
Our_Layer PROC FAR
          ASSUME CS:CSEG,DS:CSEG        ;M†ste deklareras i denna del som
                                        ;f”rblir i minnet
        push ds                         ;DS-registrets v„rde sparas f”r
                                        ;att †terh„mtas vid †terhoppet
        push cs                         ;Under arbetet i 'Our_Layer' m†ste
        pop ds                          ;DS ha samma v„rde som CS annars
                                        ;kommer l„sning/skrivning fr†n/till
                                        ;minne att g† till fel datasegment

        sti                             ;F”r ordningens skull f”r att
                                        ;m”jligg”ra nytt interrupt

        pushf                           ;ett INT simuleras
        call Org_Rutin                  ;Originalrutinen anropas

;---------------------------------------------------------------------
        call My_Rutin
;---------------------------------------------------------------------

        pop ds                          ;Det v„rde DS hade vid inhopp
                                        ;†terh„mtas
        iret                            ;Kontrollen tillbaka till
                                        ;anropande program (DOS)

Our_Layer ENDP

;-----------------------------------------------------------------------

My_Rutin PROC NEAR                          ;CLS (Medium Level)
         ASSUME CS:CSEG,DS:CSEG

        push ax
        mov ah,0fh
        int 10h
        mov ah,00h
        int 10h
        pop ax
        ret

My_Rutin ENDP
;-----------------------------------------------------------------------

End_TSR:                                ;Minnesresident del slut
;-----------------------------------------------------------------------
;======= Ladda 0000:03f0 med IRET och
;======= ladda 0000:0180-0000:0183 med f0 03 00 00 (Vektorn)

Load_Vector PROC NEAR

        push ax
        push bx
        push es

        mov ax,0000h
        mov es,ax

;------ IRET -----------------------------------------------------------

        mov bx,03f0h
        mov al,0cfh
        mov es:[bx],al

;------ Vektorn --------------------------------------------------------

        mov ax,03f0h                    ;Offset
        mov bx,0180h
        mov es:[bx],ax
        mov ax,0000h                    ;Segment
        inc bx
        inc bx
        mov es:[bx],ax
;------------------------------------------------------------------------
        pop es
        pop bx
        pop ax
        ret

Load_Vector ENDP
;========================================================================

Install_TSR:
        call Load_Vector
        TSR_Inst 60h

;-------------------------------------------------------------------------
CSEG    ENDS
        END Start
;--------------------------------------------------------------------------
.

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