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USERS MANUAL
X.00 A Low Level Serial I/O Communications Driver
for MS DOS and like Operating Systems.
Copyright (c) 1993 by Raymond L. Gwinn
12469 Cavalier Drive
Woodbridge, Virginia 22192
All Rights Reserved
May 22, 1993
Fidonet address 1:265/104 (Routed mail only)
Compuserve 72570,157
Internet 72570.157@Compuserve.com
Data 703-494-0098
FAX 703-494-0595
i
INTRODUCTION
Previously, the documentation for X00 was little more than a
collection of notes. The notes were added to as the development
process continued and enhancements were made. I honestly did not
suspect that X00 would become as widely used as it is. This
manual is an attempt at some decent documentation for X00.
But who do I document for? The user that is setting up a BBS
just wants to get X00 installed and to move on to more important
things. The user that is having problems needs information about
serial I/O communications in general and the PC specifically.
The application developer (programmer) needs detailed information
about each individual function and the information generated.
This manual is intended for the X00 user. A separate Application
Programmers manual is being written.
This manual and the software distributed with it is provided with
no guarantees. Use at your own risk.
ii
TABLE OF CONTENTS
WHAT IS X00 . . . . . . . . . . . . . . . . . . . . . . . . . 1
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Licensing Information . . . . . . . . . . . . . . . . . . . . 2
Non-Commercial License . . . . . . . . . . . . . . . . . 2
Commercial License . . . . . . . . . . . . . . . . . . . 2
Commercial license fasttrack . . . . . . . . . . . . . . 4
GETTING STARTED . . . . . . . . . . . . . . . . . . . . . . . 5
Installing X00 . . . . . . . . . . . . . . . . . . . . . 5
Quick Start . . . . . . . . . . . . . . . . . . . . . . 5
OVERVIEW OF X00 USAGE . . . . . . . . . . . . . . . . . . . . 6
General Information . . . . . . . . . . . . . . . . . . 6
X00 loaded as a DOS Device Driver . . . . . . . . . 6
X00 loaded as a TSR . . . . . . . . . . . . . . . . 6
COMn and PORTn . . . . . . . . . . . . . . . . . . 6
COMMAND LINE OPTIONS . . . . . . . . . . . . . . . . . . . . 7
Specifying number of ports . . . . . . . . . . . . . . . 7
B option, Locking Baud, Data, Parity and Stop bits . . . 7
Valid locked baud rates . . . . . . . . . . . . . . . . 8
Eliminate . . . . . . . . . . . . . . . . . . . . . . . 8
Defer . . . . . . . . . . . . . . . . . . . . . . . . . 8
DV . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . 9
NOFIFO . . . . . . . . . . . . . . . . . . . . . . . . 10
NOPOST . . . . . . . . . . . . . . . . . . . . . . . . 10
R, Set Receive Buffer Size . . . . . . . . . . . . . . 10
T, Set Transmit Buffer Size . . . . . . . . . . . . . 11
VP or Master Interrupt Enable . . . . . . . . . . . . 11
Mapping port assignments . . . . . . . . . . . . . . . 11
Un-installing X00 . . . . . . . . . . . . . . . . . . 12
Multi-Tasking . . . . . . . . . . . . . . . . . . . . . . . 13
THE BIOS INT 14h EMULATOR . . . . . . . . . . . . . . . . . 15
IRQ SHARING . . . . . . . . . . . . . . . . . . . . . . . . 16
Appendix A, Hardware Port and IRQ Assignments . . . . . . . 17
Addresses and IRQs for COM1 and COM2 . . . . . . . . . 17
Defacto standard for COM3 and COM4 . . . . . . . . . . 17
Addresses and IRQ for COM3 through COM8 on the PS/2 . 17
Appendix B, SIO Chips . . . . . . . . . . . . . . . . . . . 18
8250 . . . . . . . . . . . . . . . . . . . . . . . . . 18
8250A . . . . . . . . . . . . . . . . . . . . . . . . 18
iii
16450 . . . . . . . . . . . . . . . . . . . . . . . . 19
16C451 . . . . . . . . . . . . . . . . . . . . . . . . 19
16550 Non A . . . . . . . . . . . . . . . . . . . . . 19
16550A . . . . . . . . . . . . . . . . . . . . . . . . 19
16550AF . . . . . . . . . . . . . . . . . . . . . . . 19
16550AFN . . . . . . . . . . . . . . . . . . . . . . . 19
16550s Made by Western Digital . . . . . . . . . . . . 20
16C551 . . . . . . . . . . . . . . . . . . . . . . . . 20
16C552 . . . . . . . . . . . . . . . . . . . . . . . . 20
82510 . . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix C, Multi-Port Serial I/0 Cards . . . . . . . . . . 21
Connect-Com 4 . . . . . . . . . . . . . . . . . . . . 21
4 and 8 Port Boards from Decision-Computer . . . . . . 21
Stargate Plus 8 board from Software Link . . . . . . . 22
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1
WHAT IS X00
X00 is a Serial Input/Output (SIO) communications driver. It
provides an interface between an application program and the
serial communications hardware.
X00 was originally designed as a FOSSIL driver. FOSSIL is an
acronym containing the first character of several communications
programs. The FOSSIL specification is basically an extension of
the PC's BIOS services for serial communications.
Except as noted in the Programmers Manual, X00 meets the FOSSIL
level 5 specification. X00 provides additional functions that
are not contained in the FOSSIL level 5 specification.
X00 only works with 8250 (TYPE) serial I/O devices. Such devices
include the 8250A, 16450, 16550, 16550A and the 82510. If you
have a PC that is an IBM or near compatible which has a serial
communication port, it is likely that it contains one of these
devices. XU, a utility distributed with X00, will identify the
existence of compatible SIO devices.
Like other Device Drivers, X00 will do very little standing
alone. There must be an application(s) program to use X00 before
you will gain benefit.
Since the introduction of the FOSSILs, a great number of new
communications programs have come into existence. I like to
think that the FOSSILs are largely responsible for this. Many
programs that contain their own communications drivers have added
FOSSIL support. One notable example is RBBS.
Many programs written to use BIOS's serial communications
services will also work with X00. This gives those programs the
benefits of buffered interrupt driven I/O.
Warranty
There is none. Use at your own risk.
2
Licensing Information
Non-Commercial License:
A non-commercial license for use of X00 is included in the
distribution file called LICENSE.TXT.
Commercial License:
Commercial Licenses will be liberally granted in return for a
donation (usually tax deductible). Each commercial license will
be individually granted. That is, there is no single policy that
can be stated here. Some generally uniform commercial license
policies follow (see next page for fasttrack licensing).
1 - X00 is usually licensed by product.
2 - All commercial licensees of X00 will receive a special copy
of X00 that will identify, at boot time, the commercial product.
3 - I may require a fully licensed, fully featured, copy of your
product for personal use on multiple computers.
4 - The required contribution, which is never to me personally,
will usually be a one time contribution of $100.00.
5 - Proof of licensing belongs to you. That is, I am not going
to be responsible for keeping records. I suggest that you keep a
copy of the donation check so that you can send me a copy if a
question arises. Otherwise you may have to make another
contribution.
6 - You may only distribute versions of X00 that contain your
product name in the X00 banner (at boot time).
7 - If you wish to have the latest version of X00 automatically
sent to you with your product name in the X00 banner, then do the
following: Send me a check for $10.00, in advance, along with a
pre-addressed mailing label. If you require a 3.5 inch diskette,
then write "3.5 inch" on the pre-addressed mailing label and send
$15.00 (instead of $10.00). For updates, the check should be
made out to Raymond L. Gwinn. The checks will be cashed when
received. Individuals that wish to receive a mailed copy of the
latest X00 version may also use this procedure. Once you have
received an update, you will need to resend the update fee and
pre-addressed mailing label if you desire to receive the next
update.
8 - Your contribution check should state "X00 Licensing
contribution" in the Memo or comment field.
3
If you write me about a commercial license (see next page),
please include a voice phone number. Your chances of receiving a
response are better if the voice phone number is included.
Correspondence should be sent to:
Raymond L. Gwinn
12469 Cavalier Drive
Woodbridge, Va. 22192
Prior to making the special version of X00 available, I may wait
for the check to clear the bank. If the check bounces, I will,
most likely, not give any further consideration to a commercial
license.
4
Commercial license fasttrack:
Remember, in general, a commercial license is required only if
you wish to distribute X00 with another software product.
1 - In a note or letter, give the name of the PRODUCT (not
company) that X00 will be distributed with. If you wish to
distribute X00 with multiple products, you will have to purchase
an equal number of licenses.
2 - Make a check out to "Young Life" for $100.00 and send it to:
Raymond L. Gwinn
12469 Cavalier Drive
Woodbridge, Va. 22192
Consultants: The licensing fee to distribute X00 with software
that you have written for a client is $1.00 per copy. The first
100 copies must be paid for in advance. That is, send a check as
described in 2 above.
Shareware: See 1 and 2 above.
Remember, I do not make any money from X00. I get too many
messages and letters for me to respond to. If you must ask
questions (before you send a check) then you are probably not
going to get an answer or license.
5
GETTING STARTED
Installing X00
X00 is distributed as a ZIP file. To extract the individual
files from the distribution file you need the program PKUNZIP or
an equivalent. PKUNZIP is a product of PKWARE and can be
downloaded from almost any bulletin board system (BBS). You
probably already have PKUNZIP and know how to use it, otherwise I
doubt that you would be reading this. When PKUNZIP is used to
extract the various files, -AV should appear after each file name
as it is extracted. In addition, the message:
Authentic files Verified!
should appear after the extraction process. If this message does
not appear, or appears with a name other than Raymond L. Gwinn,
the file is not an original X00 distribution file.
The only file that the basic user actually needs is X00.SYS.
Copy this file to a convenient directory or subdirectory on your
system. I suggest that all users also install XU.EXE also. XU
can provide important information about X00 that may be helpful
when problems occur.
Quick Start
Copy X00.SYS and XU.EXE to the root directory of your boot drive
or diskette.
If you are going to use standard communications ports, either
COM1 or COM2 on a PC or AT, or COM1 through COM8 on a PS/2, then
add the following line to your CONFIG.SYS file:
DEVICE=X00.SYS E
If you wish to have more than one communications port active
simultaneously, then modify the command line to include the
number of simultaneously active ports you wish to support. For
example, if you are using DESQview and you wish to run a BBS in
two different windows, then add the following line to your
CONFIG.SYS file:
DEVICE=X00.SYS E 2
It should be noted that the above command tells X00 how many
ports that are to be used simultaneously, not which ports. The
application program may use ANY 2 serial ports in any order.
If your setup is more complex, you must read on.
6
OVERVIEW OF X00 USAGE
General Information
Things can get a little confusing here. At the time of this
writing, X00 is almost (if not completely) unique in its ability
to function as a DOS device driver or as a Terminate (or Torment)
and Stay Resident program (TSR).
X00 loaded as a DOS Device Driver
If X00 is to be used as a DOS device driver, it must be installed
using the CONFIG.SYS file. For a precise description of the
CONFIG.SYS file and its function, please refer to your DOS
manual. Basically, you use a text editor to add a line to the
CONFIG.SYS file. The line that you add is DEVICE=X00.SYS
followed by optional parameters. The optional parameters will be
described later. If X00.SYS is not in the current directory you
will need to provide a DOS path to the directory containing X00.
For example, if X00.SYS is in a subdirectory called COMM on the
hard disk drive C, the line in the CONFIG.SYS file would be
DEVICE=C:\COMM\X00.SYS.
X00 loaded as a TSR
If X00 is to be used as a Terminate and Stay Resident (TSR)
program, then you must rename or copy X00.SYS to X00.EXE. The
EXE version of X00 must be in the current directory or in a
directory in the DOS path when it is executed. X00.EXE is
executed like any other DOS program. That is, you type X00 at
the DOS prompt followed by any optional parameters. In reality,
you will probably be using a batch file to execute X00.
COMn and PORTn
X00 allows communications ports to be swapped around. That is,
the serial port that DOS calls COM1 can be mapped (reassigned) to
any X00 port. Therefore, when a reference in this document is
made about PORTn, it refers to the serial I/O device that is
mapped to that X00 port. When a reference is made to COM1
through COM8, it refers to the serial I/O device that DOS
knows/uses as COMn. Also worth noting is that DOS numbers the
serial I/0 devices starting at 1 (COM1 through COM8) and X00
numbers them starting at 0 (PORT0 through PORT7).
X00's default is to assign PORT0 through PORT7 to COM1 through
COM8.
7
COMMAND LINE OPTIONS
The command line options are included in the command line that
invokes X00. In several cases only the first 1 or 2 characters
of the option need be entered. In other cases, the entire option
name must be spelled out. Unless otherwise stated in the
following descriptions, the entire option name must be spelled
out. The parameters are given one after another on the same line
and in any order. The length of the command line is limited only
by DOS.
Specifying number of ports
If a single decimal number is in the X00 command line, it
specifies the number of ports that X00 is to simultaneously
support. The default is one port. The maximum value of the
number of ports is 4 for non PS/2 systems and 8 for PS/2 systems.
If you desire to use more than 4 ports on a non PS/2, each port
address must be specified (see mapping port assignments below).
Input and output buffers are allocated for each of the ports
specified. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS 3
DEVICE=X00.SYS 8
When X00 is loaded as a TSR
X00 3
X00 8
B option, Locking Baud, Data, Parity and Stop bits
Normally, the application program sets the baud rate and other
parameters controlling the serial I/O hardware. Some modems
provide better performance when the communications from the
computer to modem is constant (Locked). That is, the computer to
modem speed is not the same as the modem to modem speed. If this
option is used, the modem must support RTS/CTS hardware
handshaking and the feature must be enabled on the modem.
The B command line option requires 2 parameters and allows an
optional third parameter. The option is specified in the form
B,PORTn,BAUD RATE,PARITY. You will most likely never want to
lock the parity, data and stop bits. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS B,0,2400 B,1,19200 or
DEVICE=X00.SYS B,1,19200,8N1
When X00 is loaded as a TSR
X00 B,0,2400 B,0,19200 or
X00 B,1,19200,8N1
8
Valid locked baud rates are: 75, 110, 135.5, 150, 300, 600, 1200,
1800, 2000, 2400, 3600, 4800, 7200, 9600, 19200, 28800, 38400,
57600, and 115200.
I can think of few conditions where it is necessary to use the
optional third parameter of the B command line option. The
optional third parameter is made up of 3 characters that specify
the locked setting for data bits per character, parity bit and
stop bit(s) in that order. The optional third parameter can be
made up of any combination of the following first, second and
third characters.
First Second Third
5 N = None 1
6 E = Even 2
7 O = Odd
8 M = Mark (always 1)
S = Space (always 0)
The first character specifies the number of data bits per
character, the second character specifies the handling of the
parity bit and the third character specifies the number of stop
bits. When 5 data bits and 2 stop bits (eg 5N2) are specified,
the number of stop bits will actually be 1.5. As stated above,
locking of the parity etc, is not advisable.
Anytime an application program attempts to program the baud rate,
parity etc, through X00, the locked values will be substituted.
Eliminate
Normally, when X00 is loaded a copyright notice is displayed for
5 seconds. Using the eliminate option will disable the 5 second
display of the copyright notice. Only the first letter (E) is
required to invoke this option. Examples of usage are:
When X00 is loaded as a Device Driver:
DEVICE=X00.SYS ELIMINATE or
DEVICE=X00.SYS E
When X00 is loaded as a TSR
X00 ELIMINATE or
X00 E
Defer
The Defer option creates problems on most systems. The Defer
option should be avoided by most users. X00 must use several of
the 80x86 interrupts. Normally, X00 will hook itself into the
80x86 interrupts when it is executed. The Defer option tells X00
9
to postpone hooking into some interrupts until an XU CAPTURE
command is executed. If the defer option is used and a
subsequent XU CAPTURE is not issued, X00 may not function
correctly. Additionally, the XU CAPTURE must be executed prior
to executing a multitasker like DESQview. Only the first 2
letters (DE) need to used to specify this option. Examples of
usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS DEFER or
DEVICE=X00.SYS DE
When X00 is loaded as a TSR
X00 DEFER or
X00 DE
The default for Defer is off. That is, X00 will by default
immediately hook into all necessary 80x86 interrupt vectors.
DV
The DV command line option is only of interest to those using
DESQview. The default for this option is off. When on (DV
specified in the command line), X00 will make DESQview Pause
calls when it seems that the application program is idle. This
may make time available for other tasks to use. Refer to your
DESQview manuals for details about the DESQview pause command.
If you are using DESQview, try the DV option. If it does not
adversely affect your system, leave it enabled (on). Examples of
usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS DV
When X00 is loaded as a TSR
X00 DV
FIFO
Only the first letter of the command (F) is required to invoke
this option. Some of the serial I/O hardware devices have First
In First Out (FIFO) buffers. This command line option is used to
specify the number of characters that X00 can load into the FIFO
during a single transmit interrupt. In general this number
should be set the size of the FIFO minus 1. For example, the
popular 16550A has a 16 byte FIFO on both transmit and received
data. Thus, if this option is used, I suggest the value of 15 be
used for the 16550A. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS FIFO=10
10
DEVICE=X00.SYS F=15
When X00 is loaded as a TSR
X00 FIFO=15
X00 F=8
The size of the receive FIFO is always set to the maximum by X00.
NOFIFO
This command line option is used to completely disable the use of
hardware FIFOs. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS NOFIFO
When X00 is loaded as a TSR
X00 NOFIFO
NOPOST
Normally, when X00 is executed, it will alter the COM1 through
COM4 hardware port addresses in BIOS RAM to match the addresses
being used by X00. By doing so, many DOOR type programs that use
INT 14h for their serial I/O will work correctly with X00
installed. This option (NOPOST) instructs X00 to leave the BIOS
RAM unchanged. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS NOPOST
When X00 is loaded as a TSR
X00 NOPOST
R, Set Receive Buffer Size
The R command line option allows the user to set the size of the
receive buffer. The default size of the receive buffer is 512
bytes. The size of the buffer must be a power of 2. Valid
buffer sizes are: 256, 512, 1024, 2048, 4096, 8192, 16384 and
32768. If an invalid buffer size is specified, the next lower
correct buffer size is used.
Many users needlessly set the size of the receive (or transmit)
buffer too large. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS R=1024
DEVICE=X00.SYS R=2048
11
When X00 is loaded as a TSR
X00 R=1024
X00 R=2048
T, Set Transmit Buffer Size
This option is identical to the R command line option (see above)
except it sets the size of the transmit buffer.
VP or Master Interrupt Enable
VP stands for Vector Port which is not a very good name for the
option. Some multiple port serial I/O cards default to only two
ports enabled when power is turned on. A specified value must be
written to an I/O port to enable the additional serial ports.
Simply stated the VP command line option says to write the given
value to the given port. Examples of usage are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS VP=03FF,80
When X00 is loaded as a TSR
X00 VP=3FF,80
Both of the above examples in effect says, write the value 80
(hex) the I/O port at 3FF.
Mapping port assignments
This is the most complicated command line option for many users.
By default, X00 maps up to 8 serial I/O ports (PORTS 0 through
7). X00 will (attempt to) determine the hardware architecture on
which it is being executed. If a PS/2 is detected then the
default Serial I/O port addresses will be set to match the PS/2
(see Appendix . If X00 detects that the system is not a PS/2
type system, then the default port addresses are as follows: 1 -
Standard addresses for COM1 and COM2, 2 - The defacto standard
for COM3 and COM4, and nothing for COM5 through COM8 (ports 4
through 7).
Port mapping is necessary if your hardware configuration does not
match the PS/2 or defacto standard for non PS/2 systems. COM1
and COM2 are the same for the PC, XT, AT and PS/2. However,
hardware specifications for COM3 through COM8 became available
only when IBM released the PS/2.
Many multiple serial port cards are available for pre PS/2
systems that use a defacto standard. The most common assignments
that I have seen for COM3 and COM4 are: COM3 at port address 3E8
12
using IRQ 3. COM4 at port address 2E8 using IRQ 4. Above the
fourth port, I have not observed anything resembling a defacto
standard.
X00 will support almost any serial I/O card. However, in most
cases, port mapping is required for anything beyond COM1 and
COM2.
Mapping port assignments uses two basic forms. They are:
PORTn=COMn,IRQn
PORTn=HEXADDRESS,IRQn
Where:
PORTn is the X00 port number and must be 0 through 7.
COMn is a standard DOS port and must be COM1 through COM8.
IRQn is the IRQ use by the serial port and must be IRQ0
through IRQ15.
HEXADDRESS is a hexadecimal I/O port address that addresses
the serial I/O device.
In both basic forms, the IRQn is optional. X00 defaults all IRQn
to IRQ3 except COM1 which defaults to IRQ4. Examples of usage
are:
When X00 is loaded as a Device Driver
DEVICE=X00.SYS 0=COM4
DEVICE=X00.SYS 0=COM4,IRQ5
DEVICE=X00.SYS 0=2E8,IRQ3
DEVICE=X00.SYS 2=2E8
When X00 is loaded as a TSR
X00 0=COM4
X00 0=COM4,IRQ5
X00 0=2E8,IRQ3
X00 2=2E8
Un-installing X00
When X00 is installed as a TSR, it can be un-installed by simply
executing X00 with no command line parameters. If you wish to be
sure that you do not accidently un-install X00, always execute it
with a harmless parameter like X00 E.
13
Multi-Tasking
By far, DESQview seems to be the multi-tasking software that X00
is most often used with. At the time of this writing, I
personally use DESQview to run a multi line BBS.
I believe it is best to load X00 before the multi-tasking program
and to load it as a device driver. This enables all windows
(tasks) access to X00. Loading X00 first also allows multiple
windows to share the same IRQ.
If you have loaded X00 prior to DESQview, you need to configure
the window for no communications. That is, answer NO to the
configuration questions, Uses Serial Ports and Optimize
communications. I also suggest that you enable printer
management within the window. Enabling printer management allows
a remote drop to DOS to work on many systems. The Optimize
communications option and the Printer management option are
established with the DESQview SETUP program. The Uses serial
ports (Y,N,1,2) option is in the "Change a Program" portion of
window configuration.
In several cases I have gained a significant increase in
performance by turning X00 on prior to executing a program. Two
notable cases are GATEWAY and DOORWAY. I used XU to turn X00 on.
For example, XU PORT:n:ON just before invoking DOORWAY or GATEWAY
produced significantly better input and output from the programs.
Depending on your environment, an XU PORT:n:OFF may have to be
issued after the program terminates. Also note that the n for
PORTn is 1 less than the n in GATEn and COMn.
The communications windows seem to work better if the ticks for
the foreground and background are set relatively low. Most
people that I have talked to use 2 ticks for both foreground and
background. Only experimentation will determine the best setting
for your system.
If you do not wish to share an IRQ, you can load X00 as a TSR
inside a DESQview window. When loaded inside a DESQview window,
X00 is only available to programs in that window. X00 should be
configured to support only 1 serial port and you should
specifically name the port that X00 will use in the command line.
For example use X00 0=COM1, instead of X00 1 or just plain X00.
Identifying the specific serial port to be used in the window
eliminates the chance that X00 will interfere with another active
window.
I strongly recommend that you use the 16550A (or later) SIO chip
if you are using a multi-tasking system of any kind.
14
Most programs written to use BIOS INT 14h will work directly with
X00's enhanced services. You should try turning X00 on using an
XU PORT:n:ON command just prior to executing the program.
Programs that do not have their own interrupt I/O will most
likely give better performance.
15
THE BIOS INT 14h EMULATOR
X00 is a BIOS INT 14h enhancement. So what is the need for a
BIOS emulator also? Well, when X00 is turned off for a given
port, it does not process the INT 14h functions using the
enhanced code. Prior to the introduction of the BIOS INT 14h
emulator, X00 simply passed calls to inactive serial ports to the
BIOS INT 14h.
Serial communications has changed considerably since the
definition of the original BIOS for the PC. However, the BIOS
services for serial communications have changed very little.
Many program are still written to use the original BIOS serial
communications services. Many older programs that use the BIOS
communications services are still widely used.
Problems occur when advanced high speed modems are used with
these programs. Many of the programs are totally unaware of the
concept of RTS/CTS handshaking that most of the high speed modems
use. The programs cannot be aware that the user may have mapped
the port addresses. BIOS for all systems (that I know of)
support only 4 serial communications ports except PS/2 systems
which support 8.
I added the BIOS emulator to X00 to support many of the programs
that are not (or cannot be) aware of the active communications
environment.
By default, X00's BIOS INT 14h emulator is enabled. It can be
disabled by adding USEBIOS to the command line that invokes X00.
When the emulator is enabled, port mapping, baud rate locking and
hardware handshaking for the serial port(s) are maintained and 8
serial ports are supported. If the serial I/O chip is FIFOed,
the emulator allows the FIFOs to be used. This means that many
programs written to use BIOS can be used in the more advanced
communications environments.
The BIOS emulator can be activated and deactivated dynamically
using XU.
16
IRQ SHARING
Sharing the same IRQ for multiple communications ports is not for
the weak of heart (or mind).
Most popular multitasking software seems to do everything they
can to prevent the sharing of a single IRQ between two or more
tasks (windows). This big brother attitude of the multitaskers
is cause of most of the problems in sharing a single IRQ between
several serial communications ports. Several communications
ports sharing a single IRQ is not too difficult to manage. The
problem is the multitaskers not allowing the sharing of an IRQ by
more than one task (window).
In any case, version 1.20 of X00 has been tested with DESQview,
RBBS and 8 comm ports sharing IRQ 3. I have also tested
MultiLink with 2 comm ports sharing the same IRQ. With
MultiLink, I had to use the NASTY option. Do not use the NASTY
option with DESQview.
The method I have developed to force sharing of an IRQ by
multiple comm ports should work on most, if not all,
multitaskers. It is too big a job, and too costly for me to test
them all.
Some general rules are as follows:
1 - X00 should be loaded before the multitasker. That is, if
your multitasker allows the loading of device drivers into each
window, DO NOT DO IT if you wish to share an IRQ. Load X00 at
boot time and it should then be available to all tasks (windows).
2 - Two different boards (plugged into different slots) can not
share the same IRQ. This is a hardware limitation and can not be
corrected by software. This means that you can not plug in two
internal modems, set them for the same IRQ and expect them to
work. This does not apply to PS/2 systems. The problem of
multiple boards sharing the same IRQ was corrected in the PS/2's
buss design.
3 - When configuring the DESQview windows, we specified NO
communications in the window. Remember, it is X00 (which is
hopefully outside any window) that is doing the actual
communications and not the application program inside the window.
4 - X00 can not (will not) share an IRQ with other software. If
you attempt to run a program in a window that uses an IRQ that is
being used by X00, the results are unpredictable.
5 - Do not load X00 into EMS memory. Loading high is okay.
17
Appendix A, Hardware Port and IRQ Assignments
I have obtained the following information from various sources.
Accuracy is not guaranteed. In fact, nothing in this document is
guaranteed.
Addresses and IRQs for COM1 and COM2
COM1 uses 03F8h and IRQ4
COM2 uses 02F8h and IRQ3
Defacto standard for COM3 and COM4 for PC, XT and AT
COM3 uses 03E8h and IRQ4
COM4 uses 02E8h and IRQ3
Addresses and IRQ for COM3 through COM8 on the PS/2
COM3 uses 3220h and IRQ3
COM4 uses 3228h and IRQ3
COM5 uses 4220h and IRQ3
COM6 uses 4228h and IRQ3
COM7 uses 5220h and IRQ3
COM8 uses 5228h and IRQ3
All PCs prior to the PS/2 only used 12 bits to address hardware
I/0 ports. Systems prior to the PS/2 and EISA can not address
the standard addresses for COM3 through COM8. If an AT of below
attempts to address COM3 through COM8 using the standard
addresses, only the low 12 bits of the address are used. That
is, the high digit of the hexadecimal address will be ignored.
This means that any reference to COM3 through COM8 will actually
address ports 220h through 22Fh.
You should avoid expansion boards that use ports 220h through
22Fh unless the expansion board is a serial I/O board.
X00 will (attempt to) determine the hardware architecture that it
is being executed on and use to appropriate port addresses as
defaults.
18
Appendix B, SIO Chips
The following is a collection of comments developed from hearsay,
random documents, experience, and technical specifications. So,
take it with a grain of salt. Order information from the various
manufactures if you want accurate information.
A very good reference book that I use is available from National
Semiconductor Corporation. It covers most of the SIO devices
(also called UARTs) that you will find in all PCs and clones.
The title of the book is Microcommunications Elements Databook.
The publication number (manual number) is 400066. I am not sure
that the book can be ordered directly from National
semiconductor. They may require that you get it from a
distributor. In any case, the address on the back of the manual
is:
National Semiconductor Corporation
2900 Semiconductor Drive
P.O. Box 58090
Santa Clara, CA 95052-8090
Tel:(408)721-5000
TWX:(910)339-9240
8250
As best that I know, the 8250 was the first SIO chip (integrated
circuit) that was used by the IBM PC and many clones. In my
opinion, it was a poor choice on the part of IBM. I feel many
superior devices, at comparable prices, were readily available.
At that time, I feel the 8251A or the 8530 would have been better
choices. I feel IBM used the 8250 to insure the PC would not
have synchronous communications capability in a standard
configuration.
From a hardware standpoint the 8250 is a relatively slow device.
It is advisable that programmers not perform successive inputs or
outputs to this device. It seems that software programs can load
the various registers of the 8250 faster than it can process the
information. The 8250 had a total of 7 registers. The
specifications state that 56kb is the maximum baud rate.
8250A
I believe the 8250A is the 8250 with some bug fixes. I have no
idea what the bugs may have been. A quick glance at the
specifications shows the speed of the 8250 and 8250A to be much
the same. The 8250A added an 8th register. This additional
register enables software to detect if an 8250 is installed. The
specifications state that 56kb is the maximum baud rate.
19
16450
The 16450 seems to be a speeded up version of the 8250A. There
is no direct way (that I know of) for software to detect the
difference between an 8250A and a 16450. I believe the 16450 was
developed to eliminate the need for software to insert delays
between successive accesses to the device. The specifications
indicate the 16450 is a much faster device than its predecessors.
The additional speed is only the speed at which the processor can
access the device. The maximum baud rate for the 16450 is still
stated at 56kb. However, I have been told by some people that
they have run the 16450 successfully at much higher speeds. I do
not believe there was ever a 16450A.
16C451
The 16C451 is a CMOS version of the 16450. CMOS is a term for
the material and manufacturing process used to make the part.
CMOS typically uses less power than other technologies. If you
are not designing hardware, you should view the 16C451 as a
16450.
16550 Non A
It is hard to find a 16550 (Non A). I was told by National
Semiconductor that they did everything they could to get all
16550s back. X00 (and XU) will detect a 16550 and tell you if
you have one. I am told that the 16550 was installed in early
PS/2 systems.
The 16550 was the first shot at a FIFOed version of the 8250
family from National semiconductor. However, I was told by
National Semiconductor that the FIFOs of the 16550 are not
reliable and they should not be enabled. X00 will treat a 16550
like a 16450. In this mode, they are reliable. National
Semiconductor would not provide me with a specification for the
16550. However, I suspect its maximum baud rate is the same as
the 16550A which is 256kb.
16550A, 16550AF and 16550AFN
In the manuals that I have, National Semiconductor does not
explain the differences between the 16550A and the 16550AF. I
suspect the AF part may have a few bug fixes. I believe the N in
AFN describes packaging, ceramic versus plastic, DIP versus
surface mount etc.
In the opinion of the author, there is no substitute for the
16550A (and its successors) in the 8250 type series. The 16550A
is compatible with software written for the entire family of 8250
20
type devices. Programs that are 16550A aware can provide much
improved performance over previous devices.
The maximum baud rate for the 16550A is specified at 256kb.
However, due to the hardware design of the PC et al, 115kb is the
maximum baud rate that can be programmed.
The 16550A can be plugged into the same socket that contains an
8250, 8250A or 16450. If your SIO expansion board has the SIO
chips in sockets, you can upgrade to the 16550A by simply
removing the old chips and replacing them with 16550As.
The key to the performance increase of the 16550A is its FIFOs.
It has 16 byte FIFOs for both transmit and receive data.
16550s Made by Western Digital
I have been told, but I have not verified for myself, that 16550s
made by Western Digital have a problem with their FIFOs when
working at 2400 baud or below.
16C551
The 16C551 is a CMOS version of the 16550AF. See the above
description of the 16C451 for a discussion of CMOS. Do not feel
you need to upgrade from a 16550A or AF to a 16C551. There is no
gain from an existing users point of view.
16C552
The 16C552 is two 16C551s on a single chip. These devices will
start showing up on multi-port serial I/O cards.
82510
I believe Intel is the only company that manufactures the 82510.
The 82510 is feature rich with several modes of operation. Its
default mode is to operate as a 16450. The 82510 has a 4 byte
FIFO for both transmit and receive data. A 4 byte FIFO is
sufficient to provide significant performance over a basic 16450.
The 82510 is small in size. Therefore, it is found in many lap
tops.
The 82510 is somewhat of a sleeper. I believe it would be much
more widely used if Intel had promoted it more. However, given a
choice between the 82510 and the 16550A, I would select the
16550A.
21
Appendix C, Multi-Port Serial I/0 Cards
I get many requests for information about multi-port serial I/O
card. I will describe the boards that I know about (or have
heard about) here. I will add to the list as I receive precise
information from users.
My personal experience is with two boards that allow multiple
serial I/O ports to share a single IRQ. The first board that I
experimented with was the Connect-Com 4 from Software Link in
Atlanta Georgia. The second board is the 4 PORT RS-232 CARD from
Decision-Computer International in Taipei, Taiwan.
Connect-Com 4
I found the manual for the Connect-Com 4 to be very confusing and
their tech support even less helpful. I was able to get the
board configured to use the standard COM1 and COM2 and the
defacto standard for COM3 and COM4. If you use the Connect-Com
4, I suggest that you use it in this manner. This means that
COM1 and COM3 will use IRQ4 and COM2 and COM4 will use IRQ3. The
Connect-Com 4 has an 8 position DIP switch for configuration.
The setting that I used was positions 2, 3, 7 and 8 ON (up), and
all other positions OFF (down). In retrospect the Connect-Com 4
seems a bit expensive. However, once configured properly, the
Connect-Com 4 worked without problem. Software Link can be
reached in Atlanta Georgia at 404-448-5465.
4 and 8 Port Boards from Decision-Computer
The second board that I have personally used, and the one that I
am currently using is from Decision-Computer. The manual is
written well enough that I did not need any technical support.
There are two boards of interest from Decision-Computer, one is a
4 port serial I/O card and the other is an 8 port serial I/O
card. I read somewhere in the documentation (which I can not
find at this time) that the boards are a clone of boards
available from AST.
The boards from Decision-Computer are configured by jumpers. I
use 4 ports of the 8 port card. I selected the (so called)
Compatible Mode. This means that the first two serial I/O ports
operate as standard COM1 and COM2 using IRQ4 and IRQ3
respectively. The jumper setting for Compatible Mode is clearly
shown in the manual (page 8 of my manual). The I/O port
addressed used in that mode are also clearly defined on the same
page.
A second jumper that must be set (JP2) defines the number of wait
states. I set the jumper in position 3 which means 2 wait
states. This was for a 20 mhz 386 system. This setting works
fine for me. More wait states may be required or less may work
22
on your system. The amount of time lost due to wait states for
serial I/O is very minimal.
The last jumper(s) for the Decision-Computer 8 port RS-232 board
is the selection of the IRQ(s) for ports other than the first 2.
I selected IRQ3 for the additional ports that I am using (I am
only using 4 of the 8). This means that the first port (COM1) is
using IRQ4, all of the other (3) ports are using IRQ3. Position
2 of JP3 (left side) is the jumper that I installed.
Stargate Plus 8 board from Software Link
Dan Fox originally helped me with the testing of multiple serial
I/O ports sharing a single IRQ. He informed me that the serial
I/O board that he uses is a Stargate Plus 8 Board. He purchased
the board from Software Link in Atlanta Georgia, 404-448-5465.
Dan has all 8 ports using IRQ3.
23
INDEX
16450 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
16550 Non A . . . . . . . . . . . . . . . . . . . . . . . . . 19
16550A . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
16550AF . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
16550AFN . . . . . . . . . . . . . . . . . . . . . . . . . . 19
16550s Made by Western Digital . . . . . . . . . . . . . . . 20
16C451 . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
16C551 . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
16C552 . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8250 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8250A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
82510 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Addresses and IRQ for COM3 through COM8 on the PS/2 . . . . . 17
Addresses and IRQs for COM1 and COM2 . . . . . . . . . . . . 17
Appendix A, Hardware Notes . . . . . . . . . . . . . . . . . 17
Appendix B, SIO Chips . . . . . . . . . . . . . . . . . . . . 18
Appendix C, Multi-Port Serial I/0 Cards . . . . . . . . . . . 21
B option, Locking Baud, Data, Parity and Stop bits . . . . . . 7
Baud rates . . . . . . . . . . . . . . . . . . . . . . . . . . 8
BIOS RAM . . . . . . . . . . . . . . . . . . . . . . . . . . 10
CAPTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
COMn and PORTn . . . . . . . . . . . . . . . . . . . . . . . . 6
CONFIG.SYS . . . . . . . . . . . . . . . . . . . . . . . . 5, 6
Defacto standard for COM3 and COM4 . . . . . . . 11, 12, 17, 21
Defer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
DESQview . . . . . . . . . . . . . . . . . . . . . 5, 9, 13, 16
DV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Eliminate . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
FIFO . . . . . . . . . . . . . . . . . . . . . 9, 10, 15, 19, 20
FOSSIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
GETTING STARTED . . . . . . . . . . . . . . . . . . . . . . . . 5
IRQ SHARING . . . . . . . . . . . . . . . . . . . . . . . . . 16
Licensing Information . . . . . . . . . . . . . . . . . . . . . 2
Commercial License . . . . . . . . . . . . . . . . . . . . 2
Commercial license fasttrack . . . . . . . . . . . . . . . 4
Non-Commercial License . . . . . . . . . . . . . . . . . . 2
Locked . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Baud . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Parity and Stop bits . . . . . . . . . . . . . . . . . . . 7
Valid locked baud rates . . . . . . . . . . . . . . . . . 8
Mapping port assignments . . . . . . . . . . . . . . . . . . 11
Multi-Tasking . . . . . . . . . . . . . . . . . . . . . . . . 13
NOFIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
NOPOST . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Number of data bits . . . . . . . . . . . . . . . . . . . . . . 8
Number of stop bits . . . . . . . . . . . . . . . . . . . . . . 8
Parity bit . . . . . . . . . . . . . . . . . . . . . . . . . . 8
PKUNZIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
24
Authentic files . . . . . . . . . . . . . . . . . . . . . 5
Port assignments . . . . . . . . . . . . . . . . . . . . . . 11
Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . 5
R, Set Receive Buffer Size . . . . . . . . . . . . . . . . . 10
RBBS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
SIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SIO Chips . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Specifying number of ports . . . . . . . . . . . . . . . . . . 7
T, Set Transmit Buffer Size . . . . . . . . . . . . . . . . . 11
Terminate and Stay Resident . . . . . . . . . . . . . . . . . . 6
THE BIOS INT 14h EMULATOR . . . . . . . . . . . . . . . . . . 15
TSR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Uninstalling X00 . . . . . . . . . . . . . . . . . . . . . . 12
VP or Master Interrupt Enable . . . . . . . . . . . . . . . . 11
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
WHAT IS X00 . . . . . . . . . . . . . . . . . . . . . . . . . . 1
