National Instruments PC-DIO-96 - page 64

Register-Level Programming Chapter 4
PC-DIO-96 User Manual 4-26 © National Instruments Corporation
; restore saved registers
ii_exit:
pop es
pop ds
pop dx
pop cx
pop bx
pop ax
pop bp
sti
ret
_install_isr endp
; remove_isr
;
; bp reg at [bp+0]
; ret addr ofs at [bp+2]
; ret addr seg at [bp+4]
;
_remove_isr proc far
cli
push ax
push bx
push cx
push dx
push ds
push es
mov ax,seg _DATA
mov ds,ax
; see if our vector is installed--if not, do not remove the vector
cmp vect_num,0 ; See if vect_num was ever set
jz short ri_exit ; Our vector never installed--exit
mov al,vect_num ; Get vector number
mov ah,35h ; Get current vector from DOS
int 21h ; Get previous int_addr in es:bx
mov cx,cs ; Prep to compare old/current vectors
mov dx,es
cmp dx,cx ; See if our vector is already there
jne short ri_exit ; Different vector segment--exit
cmp bx,offset _isr_handler
jne short ri_exit ; Different vector offset--exit
; restore old mask and vector values