parallel计算机并口(打印口).docVIP

Use of a PC Printer Port for Control and Data Acquisition by Peter H. Andersonpha@Department of Electrical EngineeringMorgan State University Abstract: A PC printer port is an inexpensive and yet powerful platform for implementing projects dealing with the control of real world peripherals. The printer port provides eight TTL outputs, five inputs and four bidirectional leads and it provides a very simple means to use the PC interrupt structure. This article discusses how to use program the printer port. A larger manual which deals with such topics as driver circuits, optoisolators, control of DC and stepping motors, infrared and radio remote control, digital and analog multiplexing, D/A and A/D is avaialable. See /~pha A special thanks to Morgan State University students Towanda Malone, Christine Samuels and H. Paul Roach for their technical contributions and to New Mexico State University student Kyle Quinnell for preparing the html file. I. Printer Port Basics A. Port Assignments Each printer port consists of three port addresses; data, status and control port. These addresses are in sequential order. That is, if the data port is at address 0x0378, the corresponding status port is at 0x0379 and the control port is at 0x037a. The following is typical. Printer Data Port Status Control LPT1 0x03bc 0x03bd 0x03be LPT2 0x0378 0x0379 0x037a LPT3 0x0278 0x0279 0x027a My experience has been that machines are assigned a base address for LPT1 of either 0x0378 or 0x03bc. To definitively identify the assignments for a particular machine, use the DOS debug program to display memory locations 0040:0008. For example: debug -d 0040:0008 L8 0040:0008 78 03 78 02 00 00 00 00 Note in the example that LPT1 is at 0x0378, LPT2 at 0x0278 and LPT3 and LPT4 are not assigned. Thus, for this hypothetical machin