How to remove TSR(Terminate-Stay-Resident) program from memmory

Vote count:

0

I have a very basic TSR code. What it does is, when i type "D" key, it will print "E" on the screen, nothing else.

What i want to do is : when i press "ESC" button i want to remove my TSR and return to original BIOS routine.

org 100h

equ 060h            

EOI            equ 020h         
Master_8259    equ 020h

main:
    call _inst_09

_inst_09:
    cli
    xor     ax, ax
    mov     es, ax
    mov     bx, [es:09h*4]
    mov     [stari_int09_off], bx 
    mov     bx, [es:09h*4+2]
    mov     [stari_int09_seg], bx

    mov     dx, tastatura
    mov     [es:09h*4], dx
    mov     ax, cs
    mov     [es:09h*4+2], ax
    sti

    mov ax,3100h
    mov dx,500
    int 21h
    ret

tastatura:  
    push    ax
    in      al, KBD             ; Ucitati scan_code iz I/O registra tastature  
    mov    [kbdata], al
    cmp byte[kbdata],20h
    je .lup
    mov     al, EOI             ; Kod za End Of Interrupt (EOI)
    out     Master_8259, al     ; Poslati EOI na Master PIC (dozvola novih prekida)
    pop     ax
    iret
.lup:
    mov al,45h
    mov ah,0eh
    int 10h
    mov     al, EOI             
    out     Master_8259, al     
    pop     ax
    iret

stari_int09_seg: dw 0
stari_int09_off: dw 0

kbdata:     db 0                                   

%include "ekran.asm"

I know that i need to uninstall my modified interupt but my program became iresponsive after i did so.

This would be the unnistaling procedure

_uninst_09:
cli
xor     ax, ax
mov     es, ax
mov     ax, [stari_int09_seg]
mov     [es:09h*4+2], ax
mov     dx, [stari_int09_off]
mov     [es:09h*4], dx
sti
ret

The trick is i dont know where to put it. I tried checking if ESC is pressed and then jump to this procedure but it seems it is not wokring.

Thanks in advance

asked 1 min ago

Bozic

18

How to remove TSR(Terminate-Stay-Resident) program from memmory