Power Programming/powerprogramming1994.iso/progtool/microcrn/issue_45.arc/TECHTP45.ARC/TECHTIPS.2

Text File | 1988-03-23 | 2KB | 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