Specifications

Little Board/P5i Technical Manual
3–20
IN AL,DX ;read data in
MOV DX,CS:Ser3
OUT DX,AL ;write data to other port
Nin2:
MOV AL,64H ;clear IRQ4 to enable new interrupt
OUT INTR,AL
MOV DX,CS:IFl1
IN AL,DX
AND AL,1 ;see if data received
JZIn1
Ninb1:
MOV DX,CS:IFl3
IN AL,DX;
AND AL,1 ;see if data received
JZ In2
POP DX
POP AX
IRET
;
; *********INTERRUPT INITIALIZATION ROUTINE*********
;
MOV DX,OFFSET SerInt
MOV AL,0Ch ;set the vector for IRQ4
PUSH DS
PUSH CS
POP DS
; set the vector for INT13 using a DOS function call
MOV AH,25h ;set the interrupt vector in AL
INT 21h ;the vector is in DS:DX
;
POP DS ;restore DS
IN AL,INTR1
AND AL,0EFh ;unmask IRQ4
OUT INTR1,AL
MOV AL,64h ;clear interrupt 4 flag
OUT INTR,AL
;
; ****************PORT ADDRESS TABLE****************
;
Ser3 DW 3E8h ;base address of Serial 3
Ser1 DW 3F8h ;base address of Serial 1
;
Ifl3 DW 3eah ;status register of Serial 3
Ifl1 DW 3fah ;status register of Serial 1
;
3.11 MULTIMODE PARALLEL PORT
The enhanced parallel printer port is a superset of the standard PC-compatible printer port. It supports
four modes of operation:
 Standard PC/AT printer port—Centronics-type output only printer port, compatible with the
original IBM PC printer port.
 Bi-directional parallel port—Sometimes called a PS/2-compatible parallel port. It behaves the same
as the standard PC/AT port on outputs, and provides an input mode as well.
 Enhanced Parallel Port (EPP)—Bi-directional parallel port, compatible with the Standard and PS/2
ports, and adding automatic read- and write-cycle modes. Automatically generates input and output