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TECHTIPS.2
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1988-03-23
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2KB
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50 lines
; Micro Cornucopia Magazine Issue #45 TECHTIPS Figure 2
; Set Up COM Ports
seg_c segment para public
assume cs:seg_c, ds:seg_c
start:
mov ax,0
mov es,ax
mov bx,0 ; initialize port count
mov dx,3FAh
in al,dx ; read port 3FAh
test al,0F8h
jnz port_2 ; port not there
inc bx ; it's there, count it
mov word ptr es:400h,3F8h ; base address to memory
port_2:
mov dx,2FAh
in al,dx ; read port 2FAh
test al,0F8h
jnz port_3 ; port not there
inc bx ; it's there, count it
mov word ptr es:402h,2F8h ; base address to memory
port_3:
mov dx,3EAh
in al,dx ; read port 3EAh
test al,0F8h
jnz port_4 ; port not there
inc bx ; it's there, count it
mov word ptr es:404h,3E8h ; base address to memory
port_4:
mov dx,2EAh
in al,dx ; port 2EAh
test al,0F8h
jnz done ; port not there
inc bx ; it's there, count it
mov word ptr es:406h,2E8h ; base address to memory
done:
mov cl,1
shl bx,cl ; shift w/zeros fill
mov al,es:411h ; get the equipment flag MSB
and al,0F1h ; zero out bits 9-11
or al,bl ; insert port count in bits 9-11
mov es:411h,al ; write data to equipment flag MSB
int 21h
seg_c ends
end start