; GAMEPORT.ASM
;
; Author: Paul Cullum
; released to the public domain
;
.MODEL TINY
.DATA
yes DB 13,10,"Game port is installed.",13,10,"$"
no DB 13,10,"Game port is not installed.",13,10,"$"
.CODE
ORG 100h
start: mov al, 1 ;value to write to port
mov dx, 201h ;port number
out dx, al ;write to port
mov cx, 0F00h ;# of loops
port_loop:
in al, dx ;read from port
and al, 0Fh ;if jstick present, then AL should be
cmp al, 0Fh ; 0Fh after ANDing with 0Fh.
je jstick_exists
loop port_loop
mov dx, OFFSET no ;gameport not installed
jmp SHORT done
jstick_exists:
mov dx, OFFSET yes ;gameport installed
done: mov ah, 9h
int 21h
mov ax, 4c00h
int 21h
END start
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