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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. The way is which data is transmitted over parallel ports varies, but a general description follows. To send a byte of data, the software outputs the byte to the data lines, then pulses the STROBE output. The device on the other end (normally a printer) then asserts its BUSY line. The PC waits for BUSY to go away before sending the next byte. In other implementations, the ACKNOWLEDGE line is used for the printer to signal to the PC that it has received the data. The other control lines are used for various purposes. On the printer side, PAPER-END is a signal to the PC that the printer is out of paper. The printer also sends a SELECTED signal to the PC indicating that it is 'on line' and ready to receive data. The ERROR signal from the printer can be used for any type of error that would cause the printer to be unable to receive data. In general, if any of these signals are asserted, BUSY is also asserted. The PC has three additional output control lines. Usage of these lines varies with the particular software and printer in use. In the original PC implementation, they are used as follows: AUTOFEED tells the printer to automatically insert a line feed after each carriage return. INIT initializes the printer upon power up. SELECT deselects the printer and takes it 'off line'. SELECT was most often used as a method to signal the operator that some attention was required. For example, when the software needed to change to a different font, it would deselect the printer. This would cause the printer to turn off its SELECTED line and its front panel light. The user would then change the print wheel in the printer and press the SELECT button on the printer. The printer would then turn on its SELECTED line signalling the software to proceed. Many printers will stay in the 'off line' condition for as long as SELECT or INIT are asserted even if the SELECT button is pressed. As stated earlier, not all of these controls lines are used in the same manner. Some of the latest laser printers on the market ignore all the control lines to it except for the STROBE line. 2 PORT TEST User's Manual 2.0 ADDRESSING SCHEMES 2.1 PORT ADDRESSING Any I/O device in a PC must be located at a particular address. Actually, a serial port consists of eight addresses and a parallel port has three. The address used to refer to a particular port is the first or BASE address. For both serial and parallel ports, this first address is where the data to be transferred is read and written. These addresses are the PHYSICAL addresses of the ports. It is where the Central Processing Unit (CPU) of the PC must read or write data to send or receive data over a port. There are no set rules for what addresses must be used for ports, but some commonly used addresses are supported by most manufacturers. Generally, the first two serial ports are at physical addresses 3F8 and 2F8. These are referred to as COM1 and COM2, the LOGICAL addresses. Generally, parallel ports are located at addresses 3BC, 378 and 278, which are referred to as LPT1, LPT2, and LPT3. Many monitor cards have a parallel port built in. In these cases, the port is usually at 3BC. NOTE: The physical addresses are shown in hexadecimal notation. 2.2 WHAT THE BIOS DOES Most PC BIOS routines do a quick check upon power up to determine how many serial and parallel ports are installed in a system. They examine specific addresses by writing to them, then reading them back to determine if a device is present at that address. The BIOS then places the address of each responding device in a table in RAM located at 40:0 for serial ports and at 40:8 for parallel ports. There are eight bytes at each of the above locations reserved for port addresses. Since a port address is two bytes, up to four serial and four parallel addresses can be put in the tables. For example, for a system with two serial ports and two parallel ports, typical tables might be: Serial Port table: Parallel port table: ADDRESS DATA ADDRESS DATA 40:0 F8 03 40:8 BC 03 40:2 F8 02 40:A 78 03 40:4 00 00 40:C 00 00 40:6 00 00 40:E 00 00 Note: The high & low bytes of the address are reversed in the tables. 3 PORT TEST User's Manual 2.3 WHAT DOS DOES After a PC has booted and the BIOS is no longer in control, DOS uses the addresses in these tables as COM1, COM2, etc. for serial ports, and LPT1, LPT2, etc. for parallel ports. For example, DOS includes a program called MODE to set various parameters such as the baud rate, of a port. In order to use the MODE command, the user must refer to the desired port by its COM or LPT assignment. The physical address used is the one stored in the table. It is very possible that COM1 in one system is not at the same physical address as COM1 in another system. In order for DOS to recognize a COM or LPT number, there must be a valid address listed in the table, and there can be no gaps. If there is a zero entry in the table, DOS considers that the end of the list. Therefore, as far as DOS is concerned, it is impossible to have a COM1 & a COM4 without having a COM2 & COM3 also! Other software may report differently as explained below. 2.4 LOGICAL VS. PHYSICAL ADDRESSES Many BIOS routines only check for two serial ports and three parallel ports. As PCs became more popular, the need for more ports grew. This fact was 'fixed' by DOS Versions 3.3 and higher, which will recognize up to four COM and four LPT ports. However, DOS will only recognize a logical port whose physical address has been placed in the RAM table. If the BIOS doesn't put the physical address there upon power up, DOS won't recognize a logical port even when the hardware is properly configured and installed! If you need to use DOS to support more ports than your BIOS will detect and install, PORT TEST can be used to place the correct address in the system tables. You can use the interactive mode, but PORT TEST's batch mode was specifically designed for this purpose. Place the command: porttest /ds /dp in your autoexec.bat file to automatically detect serial and detect parallel ports in your system upon power up. These ports will now be recognized by DOS. See "Command Line Parameters" for more information. NOTE: Many application programs do not use DOS to interface to ports, so that it may not be necessary to include a port's address in the system tables. However, you must place the address in the table in order to test a port with PORT TEST. Considerable confusion exists regarding proper logical and physical port address. Strictly speaking, there is no proper physical address for any of the logical ports. The logical port structure permits any physical address to be placed into its tables. 4 PORT TEST User's Manual Many application programs access ports directly, and do not use the built in routines in the hardware's BIOS. This is usually done because the application needs a more sophisticated device driver than is provided by the BIOS. When this is the case, the logical port addresses are not always used properly. Some applications access ports directly, but properly determine the physical address from the logical address by using the table at 40:0. Other programs do not use logical addresses at all, and just refer to physical addresses. Still others convert logical to physical addresses using their own table. In this case, the program could report that there is a COM1 and a COM4 installed with no COM2 or COM3! 2.5 INTERRUPT USAGE In addition to a serial port's registers, the ACE also has the ability to interrupt the processor, either after it has transmitted a byte of data, or after it has received one. Ideally, the interrupt request line that each port uses should be unique, but there are not always enough interrupts to go around. Therefore, interrupts are sometimes used by more than one device. This is ok as long as only one of the devices is active at a time. A standard PC has eight hardware interrupt request lines. Often, IRQ4 is used for the serial port at address 3F8 and IRQ3 is used for the port at address 2F8. This is what PORT TEST assumes unless told otherwise. For other serial ports, the user must assign the proper IRQ number (if any) in PORT TEST. If left unassigned, PORT TEST will skip the interrupt tests. Most I/O cards have jumpers to select which interrupt will be used. If there are conflicts, the user should examine these jumpers to determine the cause of conflict. Some parallel ports can be configured to use IRQ7. When enabled, the processor will receive an interrupt when /ACKNOWLEDGE (pin 10) transitions from high to low. This is not supported on all cards and few applications use this feature. PORT TEST does not test parallel port interrupts. 5 PORT TEST User's Manual 3.0 SERIAL AND PARALLEL TESTS Detailed information on the content of the tests is in the manual which comes with the registered version of PORT TEST. 6 PORT TEST User's Manual 4.0 COMMAND LINE PARAMETERS In addition to its interactive mode, PORT TEST supports several command line parameters as follows: Usage: porttest [mode switches] [batch commands] All command line parameters are optional. mode switches: /p = Use the system's default print screen handler Normally PORT TEST uses its own print screen handler so that linedraw and other non printable characters are replaced before printing. If your printer has the capability to print these characters, then use this command line option to turn off PORT TEST's character translation when doing a Print Screen. /m = force Monochrome on color monitors /i force interactive mode (default when no batch args) batch commands: detectserial OR ds -> detect serial ports detectparallel OR dp -> detect parallel ports addserial <hex> OR as <hex> -> add serial port addparallel <hex> OR ap <hex> -> add parallel port com#:<b>,<p>,<d>,<s> -> set serial parameters addserial <hex>:<b>,<p>,<d>,<s> -> add and set parameters delete com# OR delete lpt# -> delete port swap com# com# OR swap lpt# lpt# -> swap ports Examples of command line usage: porttest ds Automatically detects serial ports and updates the table. porttest as 280 Adds address 0280 hex to the serial port table as the next logical com port. porttest com3:9600,n,8,1 Set baud rate, parity, data bits, and stop bits for a serial port. porttest swap lpt1 lpt2 Swaps table addresses for lpt1 and lpt2. 7 PORT TEST User's Manual CUSTOMER FEEDBACK FORM We continue to strive to provide a quality product. Your comments, suggestions, criticisms, etc. are most welcome. Just fill out this form and send or fax it to us. Brand and model of computer:______________________________ Comment ( ) Suggestion ( ) Criticism ( ) Problem ( ) Other_____________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ Name: _____________________________________ Company: __________________________________ Address: __________________________________ City, State, Zip: _________________________ Phone: ______________________ Fax: ______ Do you need a reply? _________ Are you a registered user? We guarantee a reply to all registered users who request one. Mail or FAX this form to: MicroSystems Development 4100 Moorpark Ave. #104 FAX: (408)296-5877 San Jose, CA 95117 USA 8 PORT TEST User's Manual