ICS Advent PCI-RS422 Series User manual

PCI-RS422 Series
Product Manual
MANUAL NUMBER : 00650-521-1B

Page - iii
FOREWORD
This product manual provides information to install, operate and or program the referenced product(s)
manufactured or distributed by ICS Advent. The following pages contain information regarding the
warranty and repair policies.
Check our Web site (www.icsadvent.com) for technical information, manuals, and BIOS updates.
Technical assistance is also available at: 800-480-0044 (U.S.) or 858-677-0877 (international).
Customer Comments: If you experience any problems with this manual or just want to provide some
feedback, please send us a message using the online "Service Form" on our Web site (www.icsadvent.com)
under "Support." Detail any errors you find. We will correct the errors or problems as soon as possible and
post the revised manual in our online Support Library. Thank you.
The information in this document is provided for reference only. ICSAdvent does not assume any liability
arising from the application or use of the information or products described herein. This document may
contain or reference information and products protected by copyrights or patents and does not convey any
license under the patent rights of ICS Advent, nor the rights of others.
Copyright © 2000, a California Corporation, 6260 Sequence Drive, San Diego, CA92121-4371. ICSAdvent
is a Registered Trademark of ICS Advent. All trademarks and registered trademarks are the property of
their respective owners. All rights reserved. Printed in the United States of America. No part of this publi-
cation may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, elec-
tronic, mechanical, photocopying, recording , or otherwise, without the prior written permission of the pub-
lisher.

Page - iv
Shipments not in compliance with this Guarantee
and Limited Warranty Return Policy will not be ac-
cepted by ICS Advent.
Guarantee
A thirty day money-back guarantee is provided on all standard products sold. Special order products are
covered by our Limited Warranty, however they may not be returned for refund or credit. EPROMs,
RAM, Flash EPROMs or other forms of solid electronic media are not returnable for credit - but for
replacement only. Extended Warranty available. Consult factory.
Refunds
In order to receive a refund on a product for the purchase price, the product must not have been
damaged by the customer or by the common carrier chosen by the customer to return the goods and
the product must be returned complete (meaning all manuals, software, cables, etc.) within 30 days of
receipt and in an as-new and resalable condition. The Return Proceduremust be followed to assure
prompt refund.
Restocking Charges
Product returned after 30 days, and before 60 days, of the purchase will be subject to a minimum20%
restocking charge and charges for any damaged or missing parts. Products not returned within 60
days of purchase, or products which are not in an as-new and re-saleable condition, are not eligible
for credit return and will be returned to the customer.
Limited Warranty
Effective April 1, 1998, all products carry a 2-year limited warranty. Within two years of purchase,
ICS Advent will repair or replace, at our option, any defective product. ICS Advent will service the
warranty for all standard catalog products for the first two years from the date of shipment.
Please note: The 2-year warranty may not apply to special promotion items. Please consult the factory for
warranty verification.
The limited warranty is void if the product has been subjected to alteration, neglect, misuse, or abuse; if any
repairs have been attempted by anyone other than ICS Advent or its authorized agent; or if the failure is
caused by accident, acts of God, or other causes beyond the control of ICS Advent or the manufacturer.
Neglect, misuse, and abuse shall include any installation, operation, or maintenance of the product other than
in accordance with the user’s manual.
No agent, dealer, distributor, service company, or other party is authorized to change, modify, or extend the
terms of this Limited Warranty in any manner whatsoever. ICS Advent reserves the right to make changes
or improvements in any product without incurring any obligation to similarly alter products previously
purchased.

Page - v
Return Procedure
For any Guarantee or Limited Warranty return, please contact ICS Advent's Customer Service at
800-480-0044 (U.S.) or 858-677-0877 (international) and obtain a Return Material Authorization (RMA)
Number. All product(s) returned to ICS Advent for service or credit must be accompanied by a Return
MaterialAuthorization (RMA) Number. Freight on all returned items mustbe prepaid by the customer who
is responsible for any loss or damage caused by common carrier in transit. Returns for Warranty must
include a Failure Report for each unit, by serial number(s), as well as a copy of the original invoice showing
date of purchase.
To reduce risk of damage, returns of product must be in an ICS Advent shipping container. If the original
container has been lost or damaged, new shipping containers may be obtained from ICS Advent Customer
Service at a nominal cost.
ICS Advent owns all parts removed from repaired products. ICS Advent uses new and reconditioned parts
made by various manufacturers in performing warranty repairs and building replacement products.
If ICS Advent repairs or replaces a product, its warranty term is not extended.
ICSAdvent will normally return your replacement or repaired items via Second DayAir. Overnight delivery
or delivery via other carriers is available at an additional charge.
Limitation of Liability
In no event shall ICS Advent be liable for any defect in hardware, software, loss, or inadequacy of data of
any kind, or for any direct, indirect, incidental, or consequential damages in connection with or arising out of
the performance or use of any product furnished hereunder. ICSAdvent liability shall in no event exceed the
purchase price of the product purchased hereunder. The foregoing limitation of liability shall be equally
applicable to any service provided by ICSAdvent or its authorized agent.
Some Sales Items and Customized Systems are not subject to the guarantee and limited warranty.
However in these instances , any deviations will be disclosed prior to sales and noted in the original invoice.
ICS Advent reserves the right to refuse returns or credits on software or special order items.

Page - vi
Advisories
Three types of advisories are used throughout the manual to stress important points or warn of potential
hazards to the user or the system. They are the Note, the Caution, and theWarning. Following is an example
of each type of advisory:
Note: The note is used to present special instruction, or to provide extra information which may
help to simplify the use of the product.
CAUTION!
A Caution is used to alert you to a situation which if ignored may cause injury or
damage equipment.
WARNING!
AWarningisusedtoalertyouofasituationwhichifignoredwillcauseseriousinjury.
Cautions and Warnings are accented with triangular symbols. The exclamation symbol is used in all cautions
and warnings to help alert you to the important instructions. The lightning flash symbol is used on the left
hand side of a caution or a warning if the advisory relates to the presence of voltage which may be of
sufficient magnitude to cause electrical shock.
Use caution when servicing any electrical component. We have tried to identify the areas which may pose
a Caution or Warning condition in this manual; however, ICS Advent does not claim to have covered all
situations which might require the use of a Caution or Warning.
You must refer to the documentation for any component you install into a computer system to ensure proper
precautions and procedures are followed.

Page - vii
Table of Contents
Chapter 1: Introduction.............................................................................................1-1
List of Figures
Figure1-1: PCI-RS422 Block Diagram .................................................................................................... 1-3
Figure3-1: PCI-COM422/485Option Selection Map................................................................................ 3-2
FigureA-1:TypicalRS485Two-Wire Multidrop Network............................................................................ A-3
List of Tables
Table 5-1: BaudRate DivisorValues....................................................................................................... 5-1
Table6-1: ConnectorPinAssignments ..................................................................................................... 6-1
TableA-1:Connections BetweenTwo RS422 Devices .............................................................................. A-1
TableA-2: RS422 Specification Summary................................................................................................. A-2
Revision 1B
December 2000
BalancedModeOperationandLoadTermination................................................................................ 1-1
COMPort Compatibility ..................................................................................................................... 1-1
Chapter 2: Installation...............................................................................................2-1
Chapter 3: Option Selection ......................................................................................3-1
Chapter 4: Address Selection...................................................................................4-1
Chapter 5: Programming ..........................................................................................5-1
Chapter 6: Connector Pin Assignments..................................................................6-1
AppendixA: Application Considerations ............................................................... A-1
CommunicationModes ...................................................................................................................... 1-2
Auto-RTS TransceiverControl ........................................................................................................... 1-2
Specifications .................................................................................................................................... 1-2
CDInstallation ................................................................................................................................... 2-1
DirectoriesCreatedon Hard Disk....................................................................................................... 2-2
InstallingtheCard .............................................................................................................................. 2-4
Input/OutputConnections .................................................................................................................. 2-5
Sample Programs .............................................................................................................................. 5-1
Initialization ....................................................................................................................................... 5-3
Reception .......................................................................................................................................... 5-3
Transmission ..................................................................................................................................... 5-5
ACCES32.DLL................................................................................................................................... 5-4
32-Bit VB 4.0 Example Code ............................................................................................................. 5-5
BalancedDifferentialSignals.............................................................................................................. A-1
RS-485DataTransmission ................................................................................................................ A-3

Page - viii
This page intentionally left blank

Page 1-1
Manual 00650-521-1
Chapter 1: Introduction
The PCI-RS422 Serial Communications Card was designed for use in PCI-Bus computers and
provides effective communication in either RS422 (EIA422) or RS485 (EIA485) over long
communication lines. The card is 4.80 inches long (122 mm) and may be installed in any 5-volt
PCI slot in IBM or compatible computers. A type 16550 buffered UART is used and, for Windows
compatibility, automatic control is included to transparently enable/disable the transmission
drivers.
Balanced Mode Operation and Load Termination
In RS422 mode, the card uses differential (or balanced) line drivers for noise immunity and to
increase the maximum distance to 4000 feet. The RS485 mode improves on RS422 with
switchable transceivers and the ability to support multiple devices on a single “party line”. The
number of devices served on a single line can be expanded by using “repeaters”.
RS422 operation permits multiple receivers on the communications lines and RS485 operation
permits up to 32 transmitters and receivers on the same set of data lines. Devices at the ends of
these networks should be terminated to avoid “ringing”. The user has the option to terminate the
transmitter and/or the receiver lines.
RS485 communications requires that a transmitter supply a bias voltage to ensure a known “zero”
state when no device is transmitting. This card supports biasing by default. If your application
requires the transmitter to be un-biased, please contact the factory.
COM Port Compatibility
A16550 UART is used as the Asynchronous Communication Element (ACE). It includes 16-byte
transmit/receive FIFO buffers to protect against lost data in multitasking operating systems, while
maintaining 100 percent compatibility with the original IBM serial port. PCI bus architecture
allows addresses between 0000 and FFF8 hex to be assigned to the cards.
The crystal oscillator on the card permits precise selection of baud rates up to 115,200 or, by
changing ajumper, up to 460,800 baud with the standard crystal oscillator. Baud rate is program
selected and rates available are listed in a table in the Programming section of this manual.
The driver/receiver used, the 75ALS176, is capable of driving extremely long communication lines
at high baud rates. It can drive up to ±60 mA on balanced lines and receive inputs as low as 200
mV differential signal superimposed on common mode noise of +12 V or -7 V. In case of
communication conflict, the driver/receivers feature thermal shutdown.

PCI-RS422 Manual
Page 1-2
Manual 00650-521-1
Communication Modes
The cards support Simplex, Half-Duplex, and Full-Duplex communications in avariety of two and
four-wire cable connections. Simplex is the simplest form of communications with transmission
occurring only in one direction. Half-Duplex allows traffic to travel in both directions, but only
one way at atime. In Full-Duplex operation, data travels in both directions at the same time.
Most RS485 communications use the Half-Duplex mode because only asingle pair of wires need
to be used and installation costs are dramatically reduced.
Auto-RTS Transceiver Control
In Windows applications the driver must be enabled and disabled as needed, allowing all cards to
share atwo-wire or four-wire cable. This card controls the driver automatically. With automatic
control, the driver is enabled when data are ready to be transmitted. The driver remains enabled
for the transmission time of one additional character after data transfer is complete and then is
disabled. The receiver is normally enabled but is disabled during transmission and then re-enabled
after transmission is completed. The card automatically adjusts its timing to the baud rate of the
data.
Specifications
Communications Interface
•I/O Connection: Shielded male D-sub 9-pin IBM AT style connector compatible
with RS422 and RS485 specifications.
•Character length: 5, 6, 7, or 8 bits.
•Parity: Even, odd or none.
•Stop Interval: 1, 1.5, or 2 bits.
•Serial Data Rates: Up to 115,200 baud, Asynchronous. Faster rates, up to 460,800
baud, are achieved by jumper selection on the card. Type 16550
buffered UART.
RS422/RS485 Differential Communication Mode
•Receiver Input Sensitivity: ±200 mV, differential input.
•Common Mode Rejection: +12V to -7V
•Drive Capability: 60 mA transmit output with thermal shutdown.
•Multipoint: Compatible with RS422 and RS485 specifications.

Page 1-3
Manual 00650-521-1
Note
Up to 32 drivers and receivers allowed on line. Serial communications ACE used is type 16550.
Driver/Receivers used are type 75ALS176.
Environmental
•Operating Temperature Range: 0 to +60 °C
•Humidity: 5% to 95%, non-condensing.
•Storage Temperature Range: -50 to +120 °C
•Size: 4.80" long (122mm) by 1.80" high (46 mm).
•Power Required: +5VDC at 175 mA typical
Figure 1-1: PCI-RS422 Block Diagram

Page 2-1
Manual 00650-521-1
Chapter 2: Installation
The software provided with this card is contained on either one CD or multiple diskettes and must
be installed onto your hard disk prior to use. To do this, perform the following steps as
appropriate for your software format and operating system. Substitute the appropriate drive letter
for your CD-ROM or disk drive where you see d: or a: respectively in the examples below.
CD Installation
DOS/WIN3.x
1. Place the CD into your CD-ROM drive.
2. Type d:K to change the active drive to the CD-ROM drive.
3. Type installK to run the install program.
4. Follow the on-screen prompts to install the software for this card.
WIN95/98/NT
1. Place the CD into your CD-ROM drive.
2. The CD should automatically run the install program after 30 seconds. If the install
program does not run, click START | RUN and type d:install, click OK or press K.
3. Follow the on-screen prompts to install the software for this card.
3.5-Inch Diskette Installation
As with any software package, you should make backup copies for everyday use and store your
original master diskettes in asafe location. The easiest way to make a backup copy is to use the
DOS DISKCOPY utility.
In a single-drive system, the command is:
diskcopy a: a:K
You will need to swap disks as requested by the system.
In a two-disk system, the command is:
diskcopy a: b:K
This will copy the contents of the master disk in drive A to the backup disk in drive B.

PCI-RS422 Manual
Page 2-2
Manual 00650-521-1
To copy the files on the master diskette to your hard disk, perform the following steps.
1. Place the master diskette into a floppy drive.
2. Change the active drive to the drive that has the diskette installed. For example, if the
diskette is in drive A, type a:K.
3. Type installK and follow the on-screen prompts.
Directories Created on the Hard Disk
The installation process will create several directories on your hard disk. If you accept the
installation defaults, the following structure will exist.
[CARDNAME]
Root or base directory containing the SETUP.EXE setup program used to help you configure
jumpers and calibrate the card.
DOS\PSAMPLES: A subdirectory of [CARDNAME] that contains Pascal samples.
DOS\CSAMPLES: A subdirectory of [CARDNAME] that contains "C" samples.
Win32\language: Subdirectories containing samples for Win95/98 and NT.
WinRisc.exe
AWindows dumb-terminal type communication program designed for RS422/485 operation.
Used primarily with Remote Data Acquisition Pods and our RS422/485 serial communication
product line. Can be used to say hello to an installed modem.
ACCES32
This directory contains the Windows 95/98/NT driver used to provide access to the hardware
registers when writing 32-bit Windows software. Several samples are provided in a variety of
languages to demonstrate how to use this driver. The DLL provides four functions (InPortB,
OutPortB, InPort, and OutPort) to access the hardware.
This directory also contains the device driver for Windows NT, ACCESNT.SYS. This device
driver provides register-level hardware access in Windows NT. Two methods of using the driver
are available, through ACCES32.DLL (recommended) and through the DeviceIOControl handles
provided by ACCESNT.SYS (slightly faster).

Page 2-3
Manual 00650-521-1
SAMPLES
Samples for using ACCES32.DLL are provided in this directory. Using this DLL not only
makes the hardware programming easier (MUCH easier), but also one source file can be used
for both Windows 95/98 and WindowsNT. One executable can run under both operating
systems and still have full access to the hardware registers. The DLL is used exactly like any
other DLL, so it is compatible with any language capable of using 32-bit DLLs. Consult the
manuals provided with your language's compiler for information on using DLLs in your
specific environment.
VBACCES
This directory contains sixteen-bit DLL drivers for use with VisualBASIC 3.0 and Windows 3.1
only. These drivers provide four functions, similar to the ACCES32.DLL. However, this DLL is
only compatible with 16-bit executables. Migration from 16-bit to 32-bit is simplified because of
the similarity between VBACCES and ACCES32.
PCIThis directory contains PCI-bus specific programs and information. If you are not using a PCI
card, this directory will not be installed.
SOURCE
Autility program is provided with source code you can use to determine allocated resources at
run-time from your own programs in DOS.
PCIFind.exe
Autility for DOS and Windows to determine what base addresses and IRQs are allocated to
installed PCI cards. This program runs two versions, depending on the operating system. Windows
95/98/NT displays a GUI interface, and modifies the registry. When run from DOS or
Windows3.x, a text interface is used. For information about the format of the registry key, consult
the card-specific samples provided with the hardware. In Windows NT, NTioPCI.SYS runs each
time the computer is booted, thereby refreshing the registry as PCI hardware is added or removed.
In Windows 95/98/NT PCIFind.EXE places itself in the boot-sequence of the OS to refresh the
registry on each power-up.
This program also provides some COM configuration when used with PCI COM ports.
Specifically, it will configure compatible COM cards for IRQ sharing and multiple port issues.
WIN32IRQ
This directory provides ageneric interface for IRQ handling in Windows 95/98/NT. Source code
is provided for the driver, greatly simplifying the creation of custom drivers for specific needs.
Samples are provided to demonstrate the use of the generic driver. Note that the use of IRQs in
near-real-time data acquisition programs requires multi-threaded application programming
techniques and must be considered an intermediate to advanced programming topic. Delphi, C++
Builder, and Visual C++ samples are provided.

PCI-RS422 Manual
Page 2-4
Manual 00650-521-1
Findbase.exe
DOS utility to determine an available base address for ISA bus , non-Plug-n-Play cards. Run this
program once, before the hardware is installed in the computer, to determine an available address
to give the card. Once the address has been determined, run the setup program provided with the
hardware to see instructions on setting the address switch and various option selections.
Poly.exe
Ageneric utility to convert atable of data into an nth order polynomial. Useful for calculating
linearization polynomial coefficients for thermocouples and other non-linear sensors.
Risc.bat
A batch file demonstrating the command line parameters of RISCTerm.exe.
RISCTerm.exe
A dumb-terminal type communication program designed for RS422/485 operation. Used primarily
with Remote Data Acquisition Pods and our RS422/485 serial communication product line. Can
be used to say hello to an installed modem. RISCTerm stands for Really Incredibly Simple
Communications TERMinal.
Installing the Card
This card can be installed in a five-volt PCI slot of an IBM or compatible computer. Before
installing the card, carefully read Chapter 3, Option Selection of this manual and configure the
card according to your requirements. Finally, our SETUP.EXE program will lead you through the
process of setting the options on the PCI-RS422 card. The setup program does not set the options.
These must be set manually by jumpers on the card.
To Install the Card
1. Turn OFF computer power.
2. Remove the computer cover.
3. Install jumpers from either Chapter 3, Option Selection of this manual or the suggestions
of our SETUP.EXE software program.
4. Install the card in an available PCI-bus slot.
5. Inspect for proper fit of the card and tighten screws. Make sure the card mounting bracket
is properly screwed into place and that there is a good chassis ground.
6. Replace the computer cover and turn the computer ON.
7. Enter the CMOS setup program of your system and verify that the PCI plug-and-play
option is set appropriately for your system. Systems running Windows95 (or any other
PNP-compliant Operating System) should set the CMOS option to OS. Systems running
under DOS, WindowsNT 3.51, Windows 3.1, or any other non-PNP-compliant Operating
System should set the PNP CMOS option to BIOS or Motherboard. Save the option and
continue booting the system.

Page 2-5
Manual 00650-521-1
Input/Output Connections
This card uses a9-pin DBM connector for I/O connections. To ensure that there is minimum
susceptibility to EMI as well as minimum radiation, it is important that the card mounting bracket
be properly screwed into place and that there be agood chassisground. Also, proper EMI cabling
techniques (cable connected to chassis ground at the aperture, shielded twisted-pair wiring, etc)
should be used for the input/output wiring.

Page 3-1
Manual 00650-521-1
Chapter 3: Option Selection
Four configuration options are determined by jumper position as described in the following
paragraphs. Locations of the jumpers are shown in Figure 3-1, Option Selection Map.
422/485
This jumper selects either RS422 or RS485 communications mode.
Termination and Bias
A transmission line should be terminated at the receiving end in its characteristic impedance in
order to avoid “ringing”. Installing a jumper at the location labeled TERMIN applies a120Sload
across the input for RS422 mode. Similarly, installing a jumper at the location labeled
TERMOUT applies 120Sacross the transmit/receive input/output for RS485 operation.
In RS485 operations, where there are multiple terminals, only the RS485 ports at each end of the
network should have terminating resistors as described above. Also, for RS485 operation, there
must be a bias on the RX+ and RX- lines. PCI-COM422/485 provides this bias.
Baud Rate
The x1/x4 jumper selects either the standard 1.8432MHz clock or 7.3728MHz clock for input to
the UART. The x4 position provides capability for baud rates up to 460,800 KHz.
Interrupts
The IRQ number is assigned by the system. Use PCIFind.EXE to determine the IRQ that was
assigned to the PCI-COM422/485 by the BIOS or Operating System. Alternately, in Windows
95/98/NT the Device Manager can be used. The PCI-COM422/485 is listed under the Data
Acquisition class. Selecting the card, clicking Properties,then selecting the Resources tab will
show the base address and IRQ assigned to the card.

PCI-RS422 Manual
Page 3-2
Manual 00650-521-1
Figure 3-1: PCI-RS422 Option Selection Map

Page 4-1
Manual 00650-521-1
Chapter 4: Address Selection
The PCI architecture is Plug-and-Play. This means the BIOS or Operating System determines the
resources assigned to PCI cards, rather than the user selecting these resources with switches or
jumpers. As a result, the card’s base address cannot be changed, it can only be determined. It’s
possible to use the Windows95/98/NT device manager to specify system resources but that method
is beyond the scope of this manual.
To determine the base address that has been assigned to the PCI-RS422, run the provided
PCIFind.EXE utility program. This utility will display a list of all of the ICS Advent cards
detected on the PCI bus, the addresses assigned to each function on each of the cards, and the
respective IRQs and DMAs (if any) allotted.
Alternately, some operating systems (Windows 95/98/2000) can be queried to determine which
resources were assigned. In these operating systems, you can use either PCIFind or the Device
Manager utility from the System Properties Applet of the control panel. These cards are installed
in the Data Acquisition class of the Device Manager list. Selecting the card then clicking
Properties,then selecting the Resources Tab will display a list of the resources allocated to the
card.
The PCI bus supports aminimum of 64K of I/O space, your card’s address may be located
anywhere in the 0400 to FFF8 hex range. PCIFind uses the Vendor ID and the Device ID to
search for your card then reads the base address and IRQ assigned. If you want to determine the
base address and IRQ assigned, use the following information:
The Vendor ID code for these cards is 494F (ASCII for “IO”).
The Device ID code for PCI-RS422 is 10C9.

Page 5-1
Manual 00650-521-1
Chapter 5: Programming
Sample Programs
There are sample programs provided with the PCI-RS422 card in C, Pascal, QuickBASIC, and
several Windows languages. DOS samples are located in the DOS directory and Windows
samples are located in the WIN32 directory.
Initialization
Initializing the chip requires knowledge of the UART’s register set. The first step is to set the baud
rate divisor. You do this by first setting the DLAB (Divisor Latch Access Bit) high. This bit is
Bit 7 at Base Address +3. In C code, the call would be:
outportb(BASEADDR +3,0x80);
You then load the divisor into Base Address +0 (low byte) and Base Address +1 (high byte). The
following equation defines the relationship between baud rate and divisor:
Desired Baud Rate = (UART clock frequency) ÷ (32 (divisor)
When the Baud jumper is in the X1 position, the UART clock frequency is 1.8432 Mhz. When the
jumper is in the X4 position, the clock frequency is 7.3728 Mhz. The following table lists popular
divisor frequencies. Note that there are two columns to consider depending on the position of the
Baud jumper.

PCI-RS422 Manual
Page 5-2
Manual 00650-521-1
Baud Rate Divisor
x1 Divisor x4 Notes Max Diff. Cable Length *
460800 N/A 1
230400 N/A 2
153600 N/A 3
115200 1 4 375 feet
57600 2 8 660 ft
38400 3 12 920 ft
28800 4 16 1165 ft
19200 6 24 1620 ft
14400 8 32 2050 ft
9600 12 48 Most common industrial
speed 4000 ft
4800 24 96 4000 ft
2400 48 192 4000 ft
1200 96 384 4000 ft
*Recommended maximum distances for differentially driven data cables (RS422 or RS485) are
for typical conditions.
Table 5-1: Baud Rate Divisor Values
In C, the code to set the chip to 9600 baud is:
outportb(BASEADDR, 0x0C);
outportb(BASEADDR +1,0);
The second initializing step is to set the Line Control Register at Base Address + 3. This register
defines word length, stop bits, parity, and the DLAB. Bits 0 and 1 control word length and allow
word lengths from 5to 8bits. Bit settings are extracted by subtracting 5 from the desired word
length. Bit 2determines the number of stop bits. There can be either one or two stop bits. If Bit 2
is set to 0, there will be one stop bit. If Bit 2 is set to 1, there will be two stop bits. Bits 3 through
6 control parity and break enable. They are not commonly used for communications and should be
set to zero. Bit 7 is the DLAB discussed earlier. It must be set to zero after the divisor is loaded
or else there will be no communication.