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1991-02-11
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PORT TEST
Comprehensive I/O Port Diagnostics for PCs
USER'S MANUAL
Version 1.1
MICROSYSTEMS DEVELOPMENT
4100 Moorpark Ave. #104
San Jose, CA 95117 USA
Phone: (408)296-4000
FAX: (408)296-5877
Copyright (C) MicroSystems Development 1990
All rights reserved
DISCLAIMER
MicroSystems Development makes no warranty of any kind, express
or implied, including without limitation, any warranties of
merchantability and/or fitness for any specific application or
use. MicroSystems Development shall not be liable for ANY loss
or damage arising from a failure of this program to operate in
the manner described, or in a manner desired by the user.
MicroSystems Development shall not be liable for any damage to
data or property which may be caused directly or indirectly by
use of the program.
IN NO EVENT SHALL MICROSYSTEMS DEVELOPMENT OR ITS SUPPLIERS BE
LIABLE FOR ANY CONSEQUENTIAL, INCIDENTAL OR EXEMPLARY DAMAGES
INCLUDING, BUT NOT LIMITED TO LOSS OF PROFITS OR REVENUES, LOSS
OF USE OF ANY PRODUCT, SERVICE OR REPLACEMENT COSTS, OR CLAIMS BY
ANY THIRD PARTY.
COPYRIGHT AND TRADEMARK INFORMATION
The software code and screen displays used in PORT TEST are the
sole property of MicroSystems Development, and may not be copied,
in any form, in whole or in part, or included in any other
program or document without the express written permission of
MicroSystems Development.
IBM, IBM PC, IBM XT and IBM AT are registered trademarks of
International Business Machines Corporation.
MS-DOS is a trademark of Microsoft Corporation.
PORT TEST is a trademark of MicroSystems Development.
MicroSystems Development is a division of
MicroSystems Development Technologies, Inc.
TABLE OF CONTENTS
1.0 BACKGROUND INFORMATION................................1
1.1 Serial Port Basics...............................1
1.2 Parallel Port Basics.............................1
2.0 ADDRESSING SCHEMES....................................3
2.1 Port Addressing..................................3
2.2 What the BIOS does...............................3
2.3 What DOS does....................................4
2.4 Logical vs. Physical Addresses...................4
2.5 Interrupt Usage..................................5
3.0 SERIAL AND PARALLEL TESTS.............................6
4.0 COMMAND LINE PARAMETERS...............................7
CUSTOMER FEEDBACK FORM.....................................8
In addition to tests and diagnostics, PORT TEST can do
the following:
porttest swap lpt1 lpt2
Swaps table addresses for lpt1 and lpt2.
porttest com3:19200,n,8,1
Set baud rate, parity, data bits, and stop bits for a serial
port.
porttest as 280
Adds address 0280 hex to the serial port table as the next
logical com port.
porttest ds
Automatically detects serial ports and updates the table.
And more...
1.0 INTRODUCTION
When computer information, known as data, is sent from one
device to another, it is carried by a wire cable. Data is
generally sent in one of two basic ways. Many bits at a time
over many wires in the cable is known as parallel transfer.
Sending one bit at a time over one wire is known as serial
transfer. Each type of transfer has its own advantages and
disadvantages. The serial or parallel connections to the
computer are called PORTS. Collectively, they are called
Input/Output, or I/O ports.
PORT TEST is comprehensive diagnostic program for I/O ports
installed in IBM PC and AT compatibles computers running DOS. It
is useful to identify ports, manipulate system tables, test the
ports, and to identify and correct problems. This manual is
intended to supplement the information provided in PORT TEST by
explaining the ways in which I/O ports are commonly used and
implemented in IBM compatible PCs. It also describes what each
test does and provides information on what to look for if any of
the tests fail.
1.1 SERIAL PORT BASICS
The PC serial port uses voltages and connectors established
by the Electronic Industries Association (EIA) standard
specification known as RS-232C. In addition to one bit of data,
other control signals are also sent and received. Sending data
one bit at a time is relatively slow, but serial ports have the
advantage of using fewer wires to connect two devices and being
able to communicate over relatively long cable distances. Most
serial ports can easily communicate over 100 ft of cable. Data
is sent using +12 volts and -12 volts to represent a 0 or a 1
data bit. In addition, there are a wide variety of serial
peripherals available which make use of the standard RS-232C
specification. Furthermore, recent advances have made serial
data transmission reliable at higher data rates. These data
rates are referred to as "baud" rates.
The heart of all serial ports is an Asychronous
Communications Element, referred to as an ACE. The CPU reads and
writes a byte (8 bits) of data to this chip, and the ACE handles
the serial transmissions and other functions related to the RS-
232C specification. The ACE used in most PC & XT type (8088 and
8086) systems is the INS8250B or equivalent. Most AT class
machines (80286 & above) use the NS16450 device. The 16450 chip
is designed to handle the higher data bus rates of the faster
computers. The serial data communications however is identical
to the 8250. It is beyond the scope of this manual to describe
the detailed workings of these chips. Refer to the
manufacturer's data sheets for more detailed information.
1.2 PARALLEL PORT BASICS
Eight bits of data are transferred at a time over PC
parallel ports. Data is sent using +5 volts and 0 volts to
1 PORT TEST User's Manual
represent a 1 or a 0 data bit. As you might expect, data can be
transferred relatively fast in this manner. The disadvantages of
this method is that more wires are needed and that most common
parallel ports can only work reliably at distances of under 20
feet.
Unlike serial ports which rely on a chip to do the data
transmission, parallel data is handled entirely with software.
Parallel ports have three registers, one for data out, one for
output control lines, and one for input control lines.