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Custom Interrupt
; interrupt vector (memory from 00000h to 00400h)
; keeps addresses of all interrupts (from 00h to 0ffh).
; you can add new interrupt or modify existing interrupts.
; address of interrupt M is stored in vector at offset M * 4,
; for example: interrupt 10h is stored at offset 10h * 4.
; first goes the offset, then segment (total of 2 bytes).
name "custint"
org 100h
start:
; set video mode to 3 - 16 color 80x25
mov ah, 0
mov al, 3
int 10h
; set es to "0000":
mov ax, 0
mov es, ax
; calculate vector address for interrupt 90h:
mov al, 90h
; multiply 90h by 4, store result in ax:
mov bl, 4h
mul bl
mov bx, ax
; copy offset into interrupt vector:
mov si, offset [test1]
mov es:[bx], si
add bx, 2
; copy segment into interrupt vector:
mov ax, cs
mov es:[bx], ax
int 90h ; test newly created interrupt.
; wait for any key press:
mov ah, 0
int 16h
int 20h ; halt execution.
; interrupt 90h starts here:
test1: pusha ; store all registers.
; make sure data segment is code segment:
push cs
pop ds
; set segment register to video memory:
mov ax, 0b800h
mov es, ax
; print message, each character is written as
; a word, high byte is color and low byte is
; ascii code:
lea si, msg ; load offset of msg to si.
mov di, 0 ; point to start of the screen.
print:
cmp [si], 0 ; if "0" then stop.
je stop
mov bl, [si] ; read ascii code from msg.
mov bh, 0f1h ; set colors: white background, blue text.
mov es:[di], bx ; write to video memory.
add di, 2 ; go to next position on screen.
inc si ; next char.
jmp print
stop:
popa ; re-store all registers.
iret ; return from interrupt.
msg db "test of custom interrupt!", 0
; interrupt vector (memory from 00000h to 00400h)
; keeps addresses of all interrupts (from 00h to 0ffh).
; you can add new interrupt or modify existing interrupts.
; address of interrupt M is stored in vector at offset M * 4,
; for example: interrupt 10h is stored at offset 10h * 4.
; first goes the offset, then segment (total of 2 bytes).
name "custint"
org 100h
start:
; set video mode to 3 - 16 color 80x25
mov ah, 0
mov al, 3
int 10h
; set es to "0000":
mov ax, 0
mov es, ax
; calculate vector address for interrupt 90h:
mov al, 90h
; multiply 90h by 4, store result in ax:
mov bl, 4h
mul bl
mov bx, ax
; copy offset into interrupt vector:
mov si, offset [test1]
mov es:[bx], si
add bx, 2
; copy segment into interrupt vector:
mov ax, cs
mov es:[bx], ax
int 90h ; test newly created interrupt.
; wait for any key press:
mov ah, 0
int 16h
int 20h ; halt execution.
; interrupt 90h starts here:
test1: pusha ; store all registers.
; make sure data segment is code segment:
push cs
pop ds
; set segment register to video memory:
mov ax, 0b800h
mov es, ax
; print message, each character is written as
; a word, high byte is color and low byte is
; ascii code:
lea si, msg ; load offset of msg to si.
mov di, 0 ; point to start of the screen.
print:
cmp [si], 0 ; if "0" then stop.
je stop
mov bl, [si] ; read ascii code from msg.
mov bh, 0f1h ; set colors: white background, blue text.
mov es:[di], bx ; write to video memory.
add di, 2 ; go to next position on screen.
inc si ; next char.
jmp print
stop:
popa ; re-store all registers.
iret ; return from interrupt.
msg db "test of custom interrupt!", 0
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