.model small
.stack 1000h
.data
count equ 1000
t equ 500  

.code 
start : 

mov ax,@data
mov ds,ax  

mov al,0b6h
out 43h , al 

mov ax ,count
out 42h,al 

mov al,ah
out 42h,al

mov al,03h
out 61h ,al

mov cx,t 

delay1:
    push cx
    mov cx,20000
    
    delay2 :
        loop delay2 
    
    pop cx
loop delay1 
        
mov ax,0h
out 61h,al 

mov ax ,4c00h
int 21h 

end start