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1994-12-08
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SIO
Technical Reference Manual
Copyright (c) 1994 by Raymond L. Gwinn
12469 Cavalier Drive
Woodbridge, Virginia 22192
All Rights Reserved
December 8, 1994
CompuServe: 71154,575
InterNet: p00321@psilink.com
Voice: 1-703-494-4673
FAX: 1-703-494-0595
BBS: 1-703-494-0098 or 199.248.240.2
INTRODUCTION
Documentation of software is often more difficult than writing
the program itself (at least it is for this author). I will do
my best though.
But who do I document for? The user that is setting up a BBS
just wants to get SIO 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.
The answer is, more than one manual is needed. This manual is
intended as a reference for use by application programmers that
desires to use SIO. A separate Users Manual is included in the
distribution file(s).
This manual and the software described is provided as is and with
no guarantees. Use at your own risk.
ii
WHAT IS SIO . . . . . . . . . . . . . . . . . . . . . . . . . 1
DISTRIBUTION, ORDERING AND SUPPORT . . . . . . . . . . . . . 2
Distribution and Ordering . . . . . . . . . . . . . . . 2
SIO Distribution and Support BBS . . . . . . . . . 2
Support . . . . . . . . . . . . . . . . . . . . . . . . 2
OS/2 Vendor Forum on
CompuServe . . . . . . . . . . . . . . . . . . 2
Development and Debugging Tools . . . . . . . . . . . . . . . 3
The Poor Man's Line Monitor (PMLM.EXE) . . . . . . . . . 3
VIEWPMLM.EXE . . . . . . . . . . . . . . . . . . . . . . 4
SIO's Utility (SU.EXE) . . . . . . . . . . . . . . . . . 4
IRQs that currently free for use . . . . . . . . . 4
File System Requests . . . . . . . . . . . . . . . . . . . . 5
Driver Initialization . . . . . . . . . . . . . . . . . 5
Read . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Input Status . . . . . . . . . . . . . . . . . . . . . . 5
Input Flush . . . . . . . . . . . . . . . . . . . . . . 6
Write . . . . . . . . . . . . . . . . . . . . . . . . . 6
Output Status . . . . . . . . . . . . . . . . . . . . . 6
Output Flush . . . . . . . . . . . . . . . . . . . . . . 6
Open . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Initial Open . . . . . . . . . . . . . . . . . . . 7
Additional Open . . . . . . . . . . . . . . . . . . 7
Close . . . . . . . . . . . . . . . . . . . . . . . . . 7
Intermediate Close . . . . . . . . . . . . . . . . 8
Last Close . . . . . . . . . . . . . . . . . . . . 8
Device I/O Control (IOCtl) Commands . . . . . . . . . . . . . 9
41h - Set Bit Rate . . . . . . . . . . . . . . . . . . 10
42h - Set Line Characteristics . . . . . . . . . . . . 11
43h - Extended Set Bit Rate . . . . . . . . . . . . . 12
44h - Transmit Byte Immediate . . . . . . . . . . . . 13
45h - Set Break Off . . . . . . . . . . . . . . . . . 13
46h - Set Modem Control Signals . . . . . . . . . . . 14
47h - Hold Transmit . . . . . . . . . . . . . . . . . 15
48h - Start Transmit . . . . . . . . . . . . . . . . . 15
4Bh - Set Break on . . . . . . . . . . . . . . . . . . 16
53h - Write Device Control Block (DCB) . . . . . . . 16
54h - Write Extended Mode Parameters . . . . . . . . . 19
61h - Query Current Bit Rate . . . . . . . . . . . . . 20
62h - Query Line Characteristics . . . . . . . . . . . 20
63h - Query Extended Bit Rate . . . . . . . . . . . . 21
64h - Query SIO Status . . . . . . . . . . . . . . . . 22
65h - Query Transmit Data Status . . . . . . . . . . . 23
66h - Query Current Modem Output Control Signals . . . 24
67h - Query Current Modem Input Signals . . . . . . . 24
68h - Query Number of Characters in Receive Buffer . . 25
6Dh - Query SIO Error . . . . . . . . . . . . . . . . 26
iii
72h - Query SIO Event Information . . . . . . . . . . 27
73h - Read Device Control Block (DCB) . . . . . . . . 28
74h - Read Enhanced Mode Parameters . . . . . . . . . 28
Differences between SIO/VSIO and COM/VCOM . . . . . . . . . 29
Appendix A, Hardware Port and IRQ Assignments . . . . . . . 30
Addresses and IRQs for COM1 and COM2 . . . . . . . . . 30
Defacto standard for COM3 and COM4 . . . . . . . . . . 30
Addresses and IRQ for COM3 through COM8 on the PS/2 . 30
Appendix B, SIO Chips . . . . . . . . . . . . . . . . . . . 31
8250 . . . . . . . . . . . . . . . . . . . . . . . . . 31
8250A . . . . . . . . . . . . . . . . . . . . . . . . 31
16450 . . . . . . . . . . . . . . . . . . . . . . . . 32
16C451 . . . . . . . . . . . . . . . . . . . . . . . . 32
16550 (Non A) . . . . . . . . . . . . . . . . . . . . 32
16550A . . . . . . . . . . . . . . . . . . . . . . . . 32
16550AF . . . . . . . . . . . . . . . . . . . . . . . 32
16550AFN . . . . . . . . . . . . . . . . . . . . . . . 32
16550s Made by Western Digital . . . . . . . . . . . . 33
16C551 . . . . . . . . . . . . . . . . . . . . . . . . 33
16C552 . . . . . . . . . . . . . . . . . . . . . . . . 33
16C554 . . . . . . . . . . . . . . . . . . . . . . . . 33
82510 . . . . . . . . . . . . . . . . . . . . . . . . 33
16650 . . . . . . . . . . . . . . . . . . . . . . . . 34
ComBic . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendix C, Multi-Port Serial I/0 Cards . . . . . . . . . . 36
STB 4COM . . . . . . . . . . . . . . . . . . . . . . . 36
Gtek BBS550 . . . . . . . . . . . . . . . . . . . . . 36
Neotech Quad Serial (MCA bus) . . . . . . . . . . . . 37
Appendix D, Advanced SIO Options . . . . . . . . . . . . . 38
Protection . . . . . . . . . . . . . . . . . . . . . . 38
Locked Baud Rate . . . . . . . . . . . . . . . . . . . 38
IRQ Reflection to DOS Process . . . . . . . . . . . . 38
I/O Port Mapping to DOS Process . . . . . . . . . . . 38
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
1
WHAT IS SIO
SIO is a Serial Input/Output (SIO) communications character
device driver. It provides an interface between application
programs and the serial communications hardware.
SIO had been designed as a high performance replacement for the
OS/2 device driver COM.SYS. This manual documents the known
differences between COM.SYS and SIO.SYS.
SIO only works with 8250 (type) serial I/O devices. Such devices
include, but is not limited to 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. SIO will identify the
type of serial devices that it finds at load time.
Like other Device Drivers, SIO will do very little standing
alone. There must be an application(s) program that makes use of
SIO's functions before one will benefit from the use of SIO.
2
DISTRIBUTION, ORDERING AND SUPPORT
Distribution and Ordering
The entire package collectively known as SIO is ShareWare. It is
not free software or freeware. See LICENSE.TXT and ORDER.TXT for
additional information. The ShareWare version of SIO is
distributed electronically. One may check their favorite
electronic hangout for the latest version of SIO. The latest
copy of the ShareWare version is always posted for downloading
from the BBS at 1-703-494-0098 or 199.248.240.2.
Registered versions of SIO are distributed by US Mail and
electronically from the SIO Distribution and Support BBS. Users
desiring to register electronically, may call the BBS and
register on line (1-703-494-0098 or 199.248.240.2) and
immediately download their registered version of SIO. Use the
ORDER command at the main BBS prompt.
Registrations/Orders can also be placed by phone, mail, FAX, and
email. See the front cover of this manual for the phone numbers
and addresses. Also see ORDER.TXT for and order form that may be
used.
Support
Extensive testing has been done to insure that this product works
on the widest possible range of OS/2 V2 (and up) systems. In
most cases, problems can be resolved by reading this manual
carefully.
Registered users of SIO can update to the latest version using
the BBS and its UPDATE command. All variations (number of ports)
of SIO are available for immediate download from the BBS.
Support is provided in section 4 of the OS/2 Vendor Forum on
CompuServe (GO OS2BVEN). Section 4 of the OS2BVEN section is
dedicated to the support of SIO.
In addition, support is provided by BBS, Email and FAX. Voice
support would overwhelm the author. If, after reading the manual
carefully, you are unable to resolve a problem, you may fill out
PROBLEM.TXT (adding information as necessary) and Email/FAX it to
one of the following:
Email
CompuServe 71154,575
Internet p00321@psilink.com
FAX 1-703-494-0595
BBS 1-703-494-0098 or 199.248.240.2
PROBLEM.TXT is included in the distribution ZIP.
3
Development and Debugging Tools
The Poor Man's Line Monitor (PMLM.EXE)
PMLM is basically of interest to developers of comm applications
and those providing technical support for those applications.
This SIO utility is released largely (in self defense) in the
hope that some users can diagnose their own problems. PMLM's
feature of saving trace information to disk will only work with
registered and beta versions of SIO.
PMLM provides basic line monitoring for OS/2, DOS and Windows
comm programs. All characters sent or received by application
programs are displayed in the upper portion of the screen.
Receive characters are displayed as "white on blue" and
transmitted characters are displayed "yellow on violet". Line
signals, such as CTS are displayed as "dim white on red" when
turned off and "bright white on red" when turned on. In
addition, a signals transition to OFF is displayed in lower case
and a signals transition to ON is displayed in upper case.
Status information is displayed in the lower part of the screen.
A bright white display means the signal is on, a dim white
indicates that the signal is off. In addition, when bright,
Rxoff and Txoff indicate the SIO has sent (Txoff) or received
(Rxoff) an Xoff, and an Xon is pending.
When a DOS or Windows session uses a comm port, an additional
line of signal status appears. This status line shows the state
of the virtual UART's signals. Only the signals which MAY be
different from the real UART's signals are shown.
"Rx Chars" and "Tx Chars" reflects the number of characters in
SIO's receive and transmit buffers respectively.
The last line on the screen shows the keys (from the keyboard)
that PMLM will recognize. The bright character shows the key to
hit for the associated function. The font keys will not work in
a windowed OS/2 session.
PMLM's command line requires one parameter, the comm port number,
and optionally accepts an additional parameter giving a save
trace file name. For example, PMLM 1 COM1INFO.TEC will monitor
COM1 and save ALL of the communications traffic in the file
COM1INFO.TRC. The trace files created by PMLM contain exactly
the same information that is displayed by PMLM, video attributes
and all.
4
VIEWPMLM.EXE may be used to view trace files created by PMLM.
VIEWPMLM.EXE requires one parameter, the trace file name. The
user can use the keys UP, DOWN, PAGEUP, PAGEDOWN, HOME, and END
to navigate the saved trace file. Registered SIO users may send
VIEWPMLM.EXE (along with saved trace files) to anyone for
technical support purposes.
VIEWPMLM can be used in native DOS, in DOS sessions under OS/2,
and in OS/2 sessions. This means that even those developers and
support people need not have OS/2 to view the captured
communications data created by PMLM.
SIO's Utility (SU.EXE)
This utility program has several useful commands. You can obtain
a list of the available commands by typing SU at any command line
prompt without any parameters. One very useful command is SU
IRQS. This command will show IRQs that currently free for use.
Commands are provided allowing user control (missing from MODE)
are available. Status commands provide a wealth of diagnostic
information.
5
File System Requests
SIO processes all file system requests made to it in one way or
another. The following file system requests and how SIO
processes them may be of use to the application programmer.
INIT Driver initialization.
Read Data transfer from driver to program.
Input Status Get input status.
Input Flush Terminate all pending input requests.
Write Data transfer from program to driver.
Output Status Get output status.
Output Flush Terminate all pending output requests.
Open Open the device for use.
Close Close the device.
IOCTL Device I/O control commands.
Each of these file system requests are discussed in more detail
in the following.
Driver Initialization
During device driver initialization the command line is parsed,
memory for data and control buffers is allocated and the system
environment is examined.
Buffers are allocated for the maximum number of ports that the
installed version of SIO can support (up to 16).
The mouse port is determined and if it is a serial mouse, that
port is excluded from use by SIO.
In the absence of any command line parameters, SIO will only
support (look for) COM1 and COM2 at the standard addresses. COM3
and up will not be supported (or looked at) unless they are
specifically identified in the SIO command line.
Read
If another read is already in progress, the process issuing the
additional read is blocked (suspended) until the previous read
command completes. When a read is started, that read is not
interrupted by additional reads. If multiple reads are issued,
they are not necessarily processed in the order they were issued.
Thus, applications may not see the read requests complete in the
order in which they were issued.
The conditions that control when the read will complete are
controlled by the active (current) DCB when the read is started.
Input Status
6
This function returns with "device busy" set if there is no data
in the receive buffer. That is, busy is returned if the process
may be blocked if the application issues a read command.
Input Flush
This function causes the receive buffer to be cleared (made
empty). Any threads that are blocked, waiting for a read, will
be restarted when this function is issued.
Write
If another write is already in progress, the process issuing the
additional write is blocked (suspended) until the previous write
command completes. When a write is started, that write is not
interrupted by additional writes. If multiple writes are issued,
they are not necessarily processed in the order they were issued.
Thus, applications may not see the write requests complete in the
order in which they were issued.
The conditions that control when the write will complete are
controlled by the current DCB when the write is started.
Output Status
This function returns with "device busy" set if the output buffer
is more than three quarters full. That is, busy is returned if
the process may be blocked if the application issues a write
command.
Output Flush
This function causes the transmit buffer to be cleared (made
empty). Any threads that are blocked, waiting for a write, will
be restarted when this function is issued.
Open
There are basically two kinds of open. They are an Initial Open
and Additional (shared) Opens. The IBM documentation calls the
initial open a First Level Open. An Initial Open is an open that
occurs when no other process has the communications port open.
An Additional Open is when an open occurs and another process
already has the communications port open. For an Additional Open
to occur, the Initial Opener must have issued an open allowing
shared access to the port.
7
Initial Open
The IRQ associated with the comm port is claimed (taken) when the
Initial Open occurs. If the associated IRQ is not available a
"Port in Use" error is returned. At the time of this writing,
the IRQ is claimed allowing sharing. However, the shared IRQ
claiming is done to circumvent anomalies in the OS, and in
actuality SIO will not concurrently share an IRQ with another
device driver. The author found it necessary to claim (reset)
all interrupts directed to the interrupt service routine in order
to prevent lock ups of a communications port. The IRQ mess may
be cleaned up at a future date when the OS problems are
corrected.
During Initial Opens, DTR and RTS are set in accordance with the
current Device Control Block (DCB) settings. If DTR Control Mode
is the "Enabled" option ( bits 1 and 0 of the DCB Flags1 byte
equal 01), then DTR is turned on. Otherwise, DTR is unchanged by
the Initial Open. Similarly, if RTS Control Mode is the
"Enabled" option ( bits 7 and 6 of the DCB Flags1 byte equal 01),
then RTS is turned on. Otherwise, RTS is unchanged by the
Initial Open.
The following actions also occur during an Initial Open:
The Xon and Xoff characters are set to 11h and 13h
respectively.
The transmit and receive buffers and structures are cleared
and re-initialized.
Status bits are reset.
If the Initial Opener is an OS/2 process (not a DOS process) then
the Read time out processing is set to "Normal" in the current
DCB.
Additional Open
A count of active opens is incremented. No changes are made to
current comm settings.
Close
There are two basic kinds of closes. They are an Intermediate
Close and a Last Close.
8
Intermediate Close
An intermediate close occurs when a process issues a close and
other processes still have the communications port opened. This
type of close simply decrements an open count and returns. No
action or changes take place at the communications port.
Last Close
The last close occurs when a process issues a close and no other
process has the communications port open. If there are any
writes pending or incomplete, the process is blocked (suspended)
until the writes complete or time out. If 60 seconds pass with
no activity at the communications port, the port is forced to
close and all writes are terminated. If any processes are
blocked (suspended) waiting on a read, they are forced to return
to the process that issued the read.
If either DTR Control Mode or RTS Control Mode are set to
"Enabled" by the current DCB, then the appropriate signal(s) is
turned off.
Finally, the IRQ is released back to the OS.
9
Device I/O Control (IOCtl) Commands
The following Generic IOCtl functions are supported by SIO.
41h - Set Bit Rate
42h - Set Line Characteristics
43h - Extended Set Bit Rate
44h - Transmit Byte Immediate
45h - Set Break Off
46h - Set Modem Control Signals
47h - Hold Transmit
48h - Start Transmit (after hold)
4Bh - Set Break On
53h - Write Device Control Block (DCB)
54h - Write Extended Mode Parameters
61h - Query Current Bit Rate
62h - Query Line Characteristics
63h - Query Extended Bit Rate
64h - Query SIO Status
65h - Query Transmit Data Status
66h - Query Current Modem Output Control Signals
67h - Query Current Modem Input Signals
68h - Query Number of Characters in Receive Buffer
69h - Query Number of Characters in Transmit Buffer
6Dh - Query SIO Error
72h - Query SIO Event Information
73h - Read Device Control Block (DCB)
74h - Read Enhanced Mode Parameters
All IOCtl functions are called with a uniform set of parameters.
This uniform set of parameters is:
DWORD Address of a data packet.
WORD Size of the data packet in bytes.
DWORD Address of the parameter packet.
WORD Size of the parameter packet in bytes.
WORD Function code.
WORD Category code (01 for SIO).
WORD Handle for the opened device.
Each IOCtl function may or may not have a data or parameter
packet. If a given IOCtl function specifies a NULL parameter or
data packet, the address of the appropriate item must be NULL
(zero) in the parameters. Passing an invalid data or parameter
packet may result in a General Protection Fault.
Each of these IOCtl commands are described in detail on the
following pages.
10
41h - Set Bit Rate
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Bit/Baud Rate │ WORD │
└───────────────────────────┴──────────┘
"Bit Rate" is any number from 1 to 65535. SIO does not
attempt to validate a given bit rate. The minimum bit rate
accepted by SIO is 50, the maximum for this IOCtl function
is 65535.
Note that the hardware may not be able to generate the given
bit rate. For example, if a computer has a standard
communications card installed and if a bit rate of 65500 is
specified, the nearest bit rate that can be generated will
be set, 57600 in this case.
To set bit rates in excess of 57600, see IOCtl function 43h,
Extended Set Bit Rate.
Some commonly used bit rates that can be set with this
function are:
50 2000
75 2400
110 3600
150 4800
300 7200
600 9600
1200 19200
1800 28800
2000 38400
2400 57600
Data Packet - None
11
42h - Set Line Characteristics
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Data Bits Per Character │ BYTE │
├───────────────────────────┼──────────┤
│ Parity Setting │ BYTE │
├───────────────────────────┼──────────┤
│ Stop Bit Setting │ BYTE │
└───────────────────────────┴──────────┘
Data Bits Per Character may be 5, 7, or 8, all other values
are invalid.
Parity Setting may have the following values, all other
values are invalid:
0 - No parity bit.
1 - Odd parity.
2 - Even parity.
3 - Mark parity (1).
4 - Space parity (0).
Stop Bit Setting may have the following values, all other
values are invalid:
0 - 1 stop bit.
1 - 1.5 stop bit (valid with 5 data bit characters).
2 - 2 stop bits.
Data Packet - None
12
43h - Extended Set Bit Rate
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Bit/Baud Rate │ DWORD │
├───────────────────────────┼──────────┤
│ Fraction │ BYTE │
└───────────────────────────┴──────────┘
"Bit Rate" is the desired bit/baud rate. The maximum bit
rate supported by SIO is determined by the installed
hardware. The IOCtl function "63h - Query Extended Bit Rate"
can be used to determine the maximum bit rate allowed for
the associated hardware.
SIO does not attempt to validate a given bit rate. This
means that the hardware may not be able to generate the
given bit rate. For example, if a computer has a standard
communications card installed and if a bit rate of 65500 is
specified, the nearest bit rate that can be generated will
be set, 57600 in this case.
"Fraction" is used to set the fractional part of the bit
rate when a high degree of accuracy is needed. As of this
writing, SIO does not support a "Fraction" other than zero.
Some commonly used bit rates that can be set with this
function are:
110 3600 115200
150 4800 230400
300 7200
600 9600
1200 19200
1800 28800
2000 38400
2400 57600
Data Packet - None
13
44h - Transmit Byte Immediate
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Character to Transmit │ BYTE │
└───────────────────────────┴──────────┘
"Character to Transmit" will be the next character loaded
into the UART for transmission. If a previous transmit
immediate byte is still pending, it is lost. This function
does not wait for the character to transmit before
returning.
This function may be used by an application program as one
of a set of functions to implement its own Xon/Xoff type
handshaking.
Data Packet - None
45h - Set Break Off
Parameter Packet - None
Look!! No Parameter Packet!
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ SIO Error Word │ WORD │
└───────────────────────────┴──────────┘
See function 6Dh "Query SIO Error" for a description of the
SIO Error Word. This function does not reset any bits in
the SIO Error Word.
14
46h - Set Modem Control Signals
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ DTR and RTS on mask │ BYTE │
├───────────────────────────┼──────────┤
│ DTR and RTS off mask │ BYTE │
└───────────────────────────┴──────────┘
Attempted changes in the the setting of signals that are
used as flow control signals are ignored. The current DCB
determines if either or both RTS and DTR are used as a flow
control signal.
The setting of bit 0 affects DTR and the setting of bit 1
affects RTS. Ones in the "on mask" specifies which of the
two signals are to be turned on, and zeros in the "off mask"
specify which of the two signals are to be turned off.
Some examples are:
On Mask Off Mask
01h 0FFh Turn DTR on
00h 0FEh Turn DTR off
02h 0FFh Turn RTS on
00h 0FDh Turn RTS off
03h 0FFh Turn RTS and DTR on
00h 0FCh Turn RTS and DTR off
If both on and off are specified for the setting of a
signal, the result is undefined.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ SIO Error Word │ WORD │
└───────────────────────────┴──────────┘
See function 6Dh "Query SIO Error" for a description of the
SIO Error Word. This function does not reset any bits in
the SIO Error Word.
15
47h - Hold Transmit
Parameter Packet - None
Data Packet - None
This function will disable the transmitter. The transmitter
will not be enabled again unless IOCtl function 48h is
issued. If the transmitter is already disabled, this call
has no effect.
This function can be used as part of a set that allows an
application to implement its own Xon/Xoff type handshaking.
Note that this is different from how COM.SYS implements this
function. COM.SYS will re-enable the transmitter if an Xon
is received while SIO will not.
48h - Start Transmit
Parameter Packet - None
Data Packet - None
This function will enable the transmitter, usually following
an IOCtl function 47h. If the transmitter is already
enabled, this call has no effect.
This function can be used as part of a set that allows an
application to implement its own Xon/Xoff type handshaking.
16
4Bh - Set Break on
Parameter Packet - None
Look!! No Parameter Packet!
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ SIO Error Word │ WORD │
└───────────────────────────┴──────────┘
See function 6Dh "Query SIO Error" for a description of the
SIO Error Word. This function does not reset any bits in
the SIO Error Word.
53h - Write Device Control Block (DCB)
This is where the action is! See also function 73h (Read DCB).
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Write Timeout │ WORD │
├───────────────────────────┼──────────┤
│ Read Timeout │ WORD │
├───────────────────────────┼──────────┤
│ Flags1 │ BYTE │
├───────────────────────────┼──────────┤
│ Flags2 │ BYTE │
├───────────────────────────┼──────────┤
│ Flags3 │ BYTE │
├───────────────────────────┼──────────┤
│ Error Replacement Byte │ BYTE │
├───────────────────────────┼──────────┤
│ Break Replacement Byte │ BYTE │
├───────────────────────────┼──────────┤
│ Xon Character │ BYTE │
├───────────────────────────┼──────────┤
│ Xoff Character │ BYTE │
└───────────────────────────┴──────────┘
"Write Timeout" The write timeout is given in hundredths of
a second, relative to zero. That is, 0 specifies 0.01
seconds and 1 specifies 0.02 seconds.
17
"Read Timeout" The read timeout is given in hundredths of a
second, relative to zero. That is, 0 specifies 0.01 seconds
and 1 specifies 0.02 seconds.
"Flags1" is a bit flag. The bits in the flag specify the
following:
Bits 1 and 0 DTR Control Mode.
00 - Disable changing DTR during Open and Close.
01 - Enable Changing DTR during Open and Close.
10 - DTR used for input handshaking (not supported
by SIO).
11 - Invalid
Bit 2, Must be zero
Bit 3, Off to ignore CTS. Forced on if RTS is handshake.
Bit 4, DSR is handshake. Not supported by SIO.
Bit 5, DCD required to transmit. Not supported by SIO.
Bit 6, DSR required to receive.
Bit 7, Must be zero.
─────────────────────────────────────
"Flags2" is a bit flag. The bits in the flag specify the
following:
Bit 0, SIO is to honor Xon/XOff received from remote.
Bit 1, SIO may send Xon/Xoff to the remote.
Bit 2, Enable error replacement character. Not supported
by SIO.
Bit 3, Enable null stripping. Not supported by SIO.
Bit 4, Enable break replacement character. Not supported
by SIO.
Bit 5, Enable Full duplex. Half duplex is not supported
by SIO.
Bits 7 and 6 RTS Control Mode
00 - Disable changing RTS during Open and Close.
01 - Enable Changing RTS during Open and Close.
10 - RTS used for input handshaking.
11 - Toggle on transmit (half duplex). Not
supported by SIO.
18
"Flags3" is a bit flag. The bits in the flag specify the
following:
Bit 0, Enable infinite write timeout processing. When
set, a write timeout will not occur.
Bits 2 and 1 Read timeout processing
00 - Invalid.
01 - Normal read time out.
10 - Wait for something. Reads will return before
a timeout occurs if something received.
11 - No Wait. Reads will return immediately with
any available data.
Bits 4 and 3 FIFO Control
00 - No change in FIFO state.
01 - Disable FIFO buffers.
10 - Enable FIFO buffers.
11 - Dynamic enabling and disabling of FIFOS.
**Note, SIO forces bits 4 and 3 to "10".
Bits 6 and 5 Set receive trigger level
00 - 1 character.
01 - 4 characters.
10 - 8 characters.
11 - 14 characters.
**Note, SIO forces bits 6 and 5 to "10".
Bit 7 Transmit load count
0 - Load 1 character.
1 - Load 16 characters.
**Note, SIO forces bit 7 to "1".
"Error Replacement Byte" Not supported by SIO.
"Break Replacement Byte" Not supported by SIO
"Xon Character" Any value, default is 11h.
"Xoff Character" Any value, default is 13h.
Data Packet - None
19
54h - Write Extended Mode Parameters
Parameter Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Enhanced Flags1 │ BYTE │
├───────────────────────────┼──────────┤
│ Reserved │ DWORD │
└───────────────────────────┴──────────┘
This function is not supported (ignored) by SIO. However
the bits are defined here for completeness.
Enhanced Flags1
Bit 0 - Enhanced mode hardware available (Query only 74h).
Bit 1 - Enable enhanced mode.
Bits 3 and 2 DMA Receive Operation
00 - Disable DMA receive capability.
01 - Enable DMA receive capability.
10 - Dedicate a DMA channel to receive.
11 - Reserved.
Bits 5 and 4 DMA Transmit Operation
00 - Disable DMA transmit capability.
01 - Enable DMA transmit capability
10 - Dedicate a DMA channel to transmit.
11 - Reserved.
Bit 6 - Receive in DMA mode (Query only, 74h).
Bit 7 - Transmit in DMA mode (Query only, 74h).
Data Packet - None.
20
61h - Query Current Bit Rate
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Bit/Baud Rate │ WORD │
└───────────────────────────┴──────────┘
See function 41h for more information.
62h - Query Line Characteristics
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Data Bits Per Character │ BYTE │
├───────────────────────────┼──────────┤
│ Parity Setting │ BYTE │
├───────────────────────────┼──────────┤
│ Stop Bit Setting │ BYTE │
├───────────────────────────┼──────────┤
│ Transmitting Break │ BYTE │
└───────────────────────────┴──────────┘
See function 42h for a definition of Data, Parity and Stop
Bits.
"Transmitting Break" is set to 1 if a break is being
transmitted. Otherwise, it is set to zero.
21
63h - Query Extended Bit Rate
Parameter Packet - None
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Current Bit/Baud Rate │ DWORD │
├───────────────────────────┼──────────┤
│ Fraction of Current │ BYTE │
├───────────────────────────┼──────────┤
│ Minimum Bit/Baud Rate │ DWORD │
├───────────────────────────┼──────────┤
│ Fraction of Minimum │ BYTE │
├───────────────────────────┼──────────┤
│ Maximum Bit/Baud Rate │ DWORD │
├───────────────────────────┼──────────┤
│ Fraction of Maximum │ BYTE │
└───────────────────────────┴──────────┘
"Current Bit/Baud Rate" is a 32 bit integer defining the
current bit rate.
"Fraction of Current" is always 0 when returned by SIO.
"Minimum Bit/Baud Rate" is the minimum value that can be
passed to SIO as a bit/baud rate.
"Fraction of Minimum" is always 0 when returned by SIO.
"Maximum Bit/Baud Rate" is the maximum value that can be
passed to SIO as a bit/baud rate.
"Fraction of Maximum" is always 0 when returned by SIO.
22
64h - Query SIO Status
Parameter Packet - None
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ SIO Status Byte │ BYTE │
└───────────────────────────┴──────────┘
"SIO Status Byte" is a bit flag. The bits have the
following meanings:
Bit 0 - Set if SIO is waiting for CTS before transmitting.
Bit 1 - Set if SIO is waiting for DSR before transmitting.
Bit 2 - Set if SIO is waiting for DCD before transmitting.
Bit 3 - Set if SIO is waiting because Xoff received or
transmitter is disabled (see function 47h).
Bit 4 - Reserved, not used by SIO.
Bit 5 - Set if SIO is waiting because break is being sent.
Bit 6 - Set if a transmit immediate is pending.
Bit 7 - Reserved, not used by SIO.
23
65h - Query Transmit Data Status
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Transmit Status │ BYTE │
└───────────────────────────┴──────────┘
"SIO Status Byte" is a bit flag. The bits have the
following meanings:
Bit 0 - Set if write in progress or pending.
Bit 1 - Set if any data is in the transmit buffer.
Bit 2 - Set if UART is currently transmitting.
Bit 3 - Set if a transmit immediate is pending.
Bit 4 - Set if an Xon needs to be sent.
Bit 5 - Set if an Xoff needs to be sent.
Bit 6 - Reserved
Bit 7 - Reserved
24
66h - Query Current Modem Output Control Signals
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Modem Output Signals │ BYTE │
└───────────────────────────┴──────────┘
"Modem Output Signals" is a bit flag. The bits have the
following meanings:
Bit 0 - Set if DTR is currently on.
Bit 1 - Set if RTS is currently on.
Bits 2-7 Reserved, set to zero by SIO.
67h - Query Current Modem Input Signals
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Modem Input Signals │ BYTE │
└───────────────────────────┴──────────┘
"Modem Output Signals" is a bit flag. The bits have the
following meanings:
Bits 0-3 Reserved, set to zero by SIO.
Bit 4 - Clear To Send (CTS) is active.
Bit 5 - Data Set Ready (DSR) is active.
Bit 6 - Ring Indicator (RI), trailing edge detected.
Bit 7 - Data Carrier Detect (DCD) is active.
25
68h - Query Number of Characters in Receive Buffer
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Number of Bytes Buffered │ WORD │
├───────────────────────────┼──────────┤
│ Byte Size of the Buffer │ WORD │
└───────────────────────────┴──────────┘
Self explaining.
69h - Query Number of Characters in Transmit Buffer
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Number of Bytes Buffered │ WORD │
├───────────────────────────┼──────────┤
│ Byte Size of the Buffer │ WORD │
└───────────────────────────┴──────────┘
Self explaining.
26
6Dh - Query SIO Error
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ SIO Error Word │ WORD │
└───────────────────────────┴──────────┘
"SIO Error Word" is a bit flag. The bits have the following
meaning:
Bit 0 - Set if a buffer overrun has occurred.
Bit 1 - Set if an overrun occurred at the UART.
Bit 2 - Set if the UART detected a parity error.
Bit 3 - Set if the UART detected a framing error.
Bits 4-15 Reserved, set to zero by SIO.
All bits of the SIO Error Word are reset prior to returning
to the caller.
27
72h - Query SIO Event Information
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ SIO Event Word │ WORD │
└───────────────────────────┴──────────┘
"SIO Event Word" is a bit flag. The bits have the following
meaning:
Bit 0 - Set when a receive character is transferred from
the UART to the receive buffer.
Bit 1 - Set when a receive (Read) timeout occurs.
Bit 2 - Set if the transmit buffer is empty.
Bit 3 - Set if Clear To Send (CTS) has changed state.
Bit 4 - Set if Data Set Ready (DSR) has changed state.
Bit 5 - Set if Data Carrier Detect (DCD) has changed
state.
Bit 6 - Set if a break has been detected.
Bit 7 - Set if a framing, parity, or overrun error has
occurred.
Bit 8 - Set if trailing edge of Ring Indicator (RI) has
occurred.
Bits 9-15 Reserved, set to zero by SIO.
All bits are reset prior to returning to the caller.
28
73h - Read Device Control Block (DCB)
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Write Timeout │ WORD │
├───────────────────────────┼──────────┤
│ Read Timeout │ WORD │
├───────────────────────────┼──────────┤
│ Flags1 │ BYTE │
├───────────────────────────┼──────────┤
│ Flags2 │ BYTE │
├───────────────────────────┼──────────┤
│ Flags3 │ BYTE │
├───────────────────────────┼──────────┤
│ Error Replacement Byte │ BYTE │
├───────────────────────────┼──────────┤
│ Break Replacement Byte │ BYTE │
├───────────────────────────┼──────────┤
│ Xon Character │ BYTE │
├───────────────────────────┼──────────┤
│ Xoff Character │ BYTE │
└───────────────────────────┴──────────┘
See function 53h for a description of the parameters.
74h - Read Enhanced Mode Parameters
Parameter Packet - None.
Data Packet
┌──────────────────────────────────────┐
│ Item Type │
├───────────────────────────┬──────────┤
│ Enhanced Flags1 │ BYTE │
├───────────────────────────┼──────────┤
│ Reserved │ DWORD │
└───────────────────────────┴──────────┘
See function 54h for a description of the Flags1 Byte.
29
Differences between SIO/VSIO and COM/VCOM
What follows is some of the differences between SIO/VSIO and
COM/VCOM that are known to the author.
1 - COM.SYS will automatically seek out and support four
comm ports, COM1 through COM4. SIO.SYS will
automatically seek out and support only COM1 and COM2.
If SIO.SYS is to support more than two comm ports, they
must be defined in the command line that loads SIO.SYS.
For example, DEVICE=SIO.SYS (COM3) (COM4) will cause
SIO.SYS to support four comm ports.
2 - In the absence of overrides in the command line,
COM.SYS will seek out four comm ports in the sequence
of I/O ports 3F8h, 2F8h, 3E8h and 2E8h. The first port
found in this sequence is given the logical name COM1,
the second is COM2 etc. This means that the comm port
at 2F8h could become COM1. In the opinion of the
author, this confuses some users to frustration.
With no command line overrides, SIO.SYS uses a fixed
I/O port concept. That is, COM1 is always at I/O port
3F8h, COM2 is always at 2F8h, etc. Another way of
looking at this is; if no comm port exists at port
3F8h, then you do not have a COM1. SIO.SYS will not
move another (found) comm port into the logical COM1
slot.
3 - VSIO opens a comm port for a DOS session with sharing
allowed. VCOM uses an "exclusive use" open for DOS
sessions.
4 - SIO.SYS will accept any number from 50 up as a valid baud
rate. For example, if an application program attempts to
set a baud rate of 9990 bps, COM.SYS will reject it and
SIO.SYS will accept it.
5 - SIO/VSIO execute faster than COM/VCOM. This means that some
applications, that are timing dependent, may not work under
SIO/VSIO that do work under COM/VCOM.
6 - SIO/VSIO provides more reliable active flow control for DOS
sessions. For example, if RTS/CTS handshaking is in use,
VSIO virtualizes the RTS settings by the DOS program while
SIO completely controls the real RTS signal. COM/VCOM
simply passes the RTS signal directly to the hardware.
7 - COM.SYS will block an application until a write completes.
SIO will return to the application program immediately if
all of the write data will fit into SIO's internal buffers.
30
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 (known to the author) prior to the PS/2 and EISA only use
10 bits to address hardware I/0 ports. Systems prior to the PS/2
and EISA can not address the standard PS/2 addresses for COM3
through COM8. If an AT or below attempts to address COM3 through
COM8 using the PS/2 addresses, only the low 10 bits of the
address are used. That is, the high 6 bits of the address will
be ignored by the hardware. This means that any reference to
COM3 through COM8 will actually address ports 220h through 22Fh
on older PCs.
One should avoid expansion boards that use ports 220h through
22Fh unless the expansion board is a serial I/O board.
SIO will (attempt to) determine the hardware architecture
(ISA/EISA and PS/2) that it is being executed on and use the
appropriate hardware port addresses for COM1 thru COM4 as
defaults.
31
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.
Very good reference books are available from National
Semiconductor Corporation. They cover most of the SIO devices
(also called UARTs) that you will find in many PCs and clones. I
am not sure that books 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 one
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 I known, 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. But, they used the 8250 and therefore we must use it.
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.
32
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. SIO 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. SIO 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 most software written for the entire family of
8250 type devices. Programs that are 16550A aware can provide
much improved performance over previous devices.
33
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 by software.
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.
16C554
The 16C554 is four 16C551s on a single chip.
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.
34
16650
The 16650 by Startech seems a good logical step in the evolution
of the 8250 type UARTs. One of the many flavors of the 16650 is
a package that is pin compatible with the 40 pin (DIP) 16550s.
This means that the 16650 can be placed into the same socket as
any 16550, 8250, etc.
The 16650 has enhanced the FIFOs to 32 bytes, added on chip flow
control ability, and increases the maximum bit rate to 460800.
The on chip flow control is a really nice feature. On chip flow
control practically eliminates the possibility of missed receive
characters. On chip flow control also means that some devices
that require immediate attention when it sends Xoff, like the
Seiko Label Printer, will work much better in environments like
OS/2 and Windows.
The 32 byte FIFOs of the 16650 is an improvement over the 16550,
but is still a disappointment. I feel that 1k, or larger, FIFOs
would have been a much better choice. When I quizzed Startech
about this, they replied that the 32 byte FIFOs were chosen to
keep the cost down. They added that if the 16650 is successful,
they plan a 16750 with larger FIFOs.
The 16650 powers up in a 16550 compatible mode, meaning most
software written for the 16550 should work. I have discovered a
serious incompatibility in the current (Oct 1994) versions of the
16650. All previous UARTS in the 8250 family will issue only a
single transmit interrupt if no additional data is sent to the
UART. The 16650 on the other hand, will issue continuous
transmit interrupts making it necessary to mask the transmit
interrupt. I quizzed Startech about this and was told that a new
revision of the chip would be available within a few months that
would correct this incompatibility.
35
ComBic
The ComBic is a very impressive UART used on the Hayes ESP card
and some others. The ComBic is basically a 16550 UART with on
chip flow control and 1k FIFOs and a maximum bit rate of 921600.
Like the 16650, on chip flow control practically eliminates the
possibility of missed receive characters. On chip flow control
also means that some devices that require immediate attention
when it sends Xoff, like the Seiko Label Printer, will work much
better in environments like OS/2 and Windows.
The ComBic has two modes of operation, compatibility mode and
enhanced mode. In compatibility mode, the UART acts as a 16550.
However, when in compatibility mode, the 1k FIFOs and on chip
flow control can still be used. In enhanced mode, software gains
the ability to look into the FIFOs and determine the exact number
of bytes loaded. This feature enables software the use block
input and output to the ComBic which greatly reduces processor
overhead.
36
Appendix C, Multi-Port Serial I/0 Cards
I have received 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 manufactures, users, or I develop it
myself.
STB 4COM (ISA bus)
I am very impressed with the STB 4COM card, they have almost got
it. Yes, it's the same company that makes the VGA cards. The
4COM card uses a 16554 which is the equivalent of four 16550A.
Comm ports can use IRQs 2/9, 3, 4, 5, 10, 11, 12, and 15. Any or
all ports can share IRQs, and they have done this right. I
tested SIO with all four ports of the 4COM on IRQ12 and they
worked correctly. The user can select any of the following I/O
port address for a comm port: 3F8, 2F8, 3E8, 2E8, 1A8, 1E8, 1F8,
2A8.
The 4COM card is priced at $110 and I ordered mine from
Prerapture Solutions which can be reached by telephone at 1-919-
286-1502 for information and foreign callers. In the US orders
can be placed by calling 1-800-735-5266. Their mailing address
is:
Prerapture Solutions
1806 Albany St.
Durham NC 27705-3135
Gtek BBS550 (ISA bus)
The Gtek BBS550 is a communications card with the equivalent of 8
16550s (in reality two 16554s) UARTS. Where were these cards 5
years ago! Like the STB 4COM, I am very impressed with the
BBS550. It has a wide range of selectable I/O port address, some
in the 16 bit range (above 3FFh) which can be very useful. I
tested the board with all 8 ports installed using IRQ3 (although
I never had more than 3 ports active at the same time). The
board performed well using shared IRQs.
The BBS550 has 8 RJ-45 connectors (10 pin), 6 of which comes
directly off the back of the card. The other two RJ-45
connectors are internal and special cables with grommets are
supplier for these 2 ports. The cables supplied with the BBS550
expands the RJ-45 out to standard DB-25 connectors.
Gtek is located in St. Louis Mississippi. Their phone number is
800-282-4835 or 601-467-8048.
37
Neotech Quad Serial (MCA bus)
Well, I just got my first PS/2 system (for testing of SIO) and I
am using the NeoTech Quad Serial card in that system. What can I
say, it works beautifully and interrupt sharing has never been a
problem on MCA systems. This card (as shipped) came with four
individual 16450 chips installed, but they were in sockets so I
installed 16550 UARTS before I installed the card. The card has
one large connector on the back of the card and the supplied
cable expands that to 4 standard DB-25 connectors. Those of you
needing a 4 port card for an MCA system contact:
Neotech Inc
30295 Solon Industrial Pkwy.
Solon, Ohio 44139
Voice (216) 248-4114
FAX (216) 248-5701
38
Appendix D, Advanced SIO Options
The following is provided for the experienced user.
Inexperienced users get themselves into a lot of trouble when
trying to use these options and they cause an inordinate number
of support problems. Therefore, the following are unsupported
options. If you use them, you must work out the problems
yourself or ask a friend how they got it working.
Protection
Placing a dash "-" in the fourth parameter position, eg
(COM1,3F8,IRQ4,-), causes SIO not to provide any protection for
that port. The OS may still protect the port somewhat. When the
dash parameter is used the port is wide open (like DOS) for any
process to access it.
Locked Baud Rate
Placing a colon and a baud rate following the communications
port, eg (COM1:38400,3F8,IRQ4), causes the port to be locked at
that baud rate. No program, OS2 or DOS, is allowed to change the
baud rate.
IRQ Reflection to DOS Process
Normally the IRQ that is reflected to a DOS process is the same
as the actual hardware IRQ. Placing a colon and an additional
IRQ following the normal IRQ, eg (COM1,3F8,IRQ12:IRQ4), causes
SIO/VSIO to reflect the IRQ to a DOS process on IRQ4 (in this
example) even though the real hardware IRQ is IRQ12. If one
wishes SIO to automatically locate the hardware IRQ, then the
following construct can be used: (COM1,3F8,:IRQ4). Notice that
the hardware IRQ is simply NOT specified.
I/O Port Mapping to DOS Process
Some DOS programs, such as CompuServe's CIM, insist that COM1 be
at I/O port 03F8, COM2 at 02F8, etc. On OS/2 systems, comm ports
can have any I/O port address as specified by a command line. If
COM1 is not at I/O port 03F8 for some DOS programs, then COM1 can
not be used by the DOS program. The SIO command line allows the
I/O ports to be mapped to a different address for DOS sessions,
eg (COM1,FF80:03F8,IRQ12:IRQ4). In this example, the real COM1
is at FF80 on IRQ12, but is reflected to DOS processes on I/O
ports 03F8 at IRQ4. It is NOT necessary to map both the I/O port
address and the IRQ. When the I/O port is mapped to a DOS
session, the UART will appear at BOTH I/O port addresses (FF80
and 03F8 in the given example).
39
Index
16450 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
16550 (Non A) . . . . . . . . . . . . . . . . . . . . . . . . 32
16550A . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
16550AF . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
16550AFN . . . . . . . . . . . . . . . . . . . . . . . . . . 32
16550s Made by Western Digital . . . . . . . . . . . . . . . 33
16650 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
16C451 . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
16C551 . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
16C552 . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
16C554 . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8250 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8250A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
82510 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Additional Open . . . . . . . . . . . . . . . . . . . . . . . . 7
Addresses and IRQ for COM3 through COM8 on the PS/2 . . . . . 30
Addresses and IRQs for COM1 and COM2 . . . . . . . . . . . . 30
Appendix A, Hardware Notes . . . . . . . . . . . . . . . . . 30
Appendix B, SIO Chips . . . . . . . . . . . . . . . . . . . . 31
Appendix C, Multi-Port Serial I/0 Cards . . . . . . . . . . . 36
Appendix D, Advanced SIO Options . . . . . . . . . . . . . . 38
BBS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Close . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
ComBic . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
CompuServe . . . . . . . . . . . . . . . . . . . . . . . . . . 2
DCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
Defacto standard for COM3 and COM4 . . . . . . . . . . . . . 30
Development and Debugging Tools . . . . . . . . . . . . . . . . 3
Device Control Block . . . . . . . . . . . . . . . . . . . . . 7
Differences between SIO/VSIO and COM/VCOM . . . . . . . . . . 29
Distribution . . . . . . . . . . . . . . . . . . . . . . . . . 2
Driver Initialization . . . . . . . . . . . . . . . . . . . . . 5
DTR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
DTR Control Mode . . . . . . . . . . . . . . . . . . . . . 7, 8
Email . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Extended Set Bit Rate . . . . . . . . . . . . . . . . . . . . 12
FAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . 32, 33
File System Requests . . . . . . . . . . . . . . . . . . . . . 5
First Level Open . . . . . . . . . . . . . . . . . . . . . . . 6
Gtek BBS550 . . . . . . . . . . . . . . . . . . . . . . . . . 36
Hold Transmit . . . . . . . . . . . . . . . . . . . . . . . . 15
I/O Port Mapping to DOS Process . . . . . . . . . . . . . . . 38
Initial Open . . . . . . . . . . . . . . . . . . . . . . . . . 7
Input Flush . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Input Status . . . . . . . . . . . . . . . . . . . . . . . . . 5
Intermediate Close . . . . . . . . . . . . . . . . . . . . . . 8
IRQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
IRQ Reflection to DOS Process . . . . . . . . . . . . . . . . 38
Last Close . . . . . . . . . . . . . . . . . . . . . . . . . . 8
40
Locked Baud Rate . . . . . . . . . . . . . . . . . . . . . . 38
National Semiconductor Corporation . . . . . . . . . . . . . 31
Neotech Quad Serial . . . . . . . . . . . . . . . . . . . . . 37
Open . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
OS2BVEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Output Flush . . . . . . . . . . . . . . . . . . . . . . . . . 6
Output Status . . . . . . . . . . . . . . . . . . . . . . . . . 6
PMLM.EXE . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Protection . . . . . . . . . . . . . . . . . . . . . . . . . 38
Query Current Bit Rate . . . . . . . . . . . . . . . . . . . 20
Query Current Modem Input Signals . . . . . . . . . . . . . . 24
Query Current Modem Output Control Signals . . . . . . . . . 24
Query Extended Bit Rate . . . . . . . . . . . . . . . . . 12, 21
Query Line Characteristics . . . . . . . . . . . . . . . . . 20
Query Number of Characters in Receive Buffer . . . . . . . . 25
Query Number of Characters in Transmit Buffer . . . . . . . . 25
Query SIO Error . . . . . . . . . . . . . . . . . . . . . . . 26
Query SIO Event Information . . . . . . . . . . . . . . . . . 27
Query SIO Status . . . . . . . . . . . . . . . . . . . . . . 22
Query Transmit Data Status . . . . . . . . . . . . . . . . . 23
Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Read Device Control Block (DCB) . . . . . . . . . . . . . . . 28
Read Enhanced Mode Parameters . . . . . . . . . . . . . . . . 28
RTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
RTS Control Mode . . . . . . . . . . . . . . . . . . . . . 7, 8
Set Bit Rate . . . . . . . . . . . . . . . . . . . . . . . . 10
Set Break Off . . . . . . . . . . . . . . . . . . . . . . . . 13
Set Break on . . . . . . . . . . . . . . . . . . . . . . . . 16
Set Line Characteristics . . . . . . . . . . . . . . . . . . 11
Set Modem Control Signals . . . . . . . . . . . . . . . . . . 14
SIO Chips . . . . . . . . . . . . . . . . . . . . . . . . . . 31
SIO's Utility (SU.EXE) . . . . . . . . . . . . . . . . . . . . 4
Start Transmit . . . . . . . . . . . . . . . . . . . . . . . 15
STB 4COM . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Transmit Byte Immediate . . . . . . . . . . . . . . . . . . . 13
UART . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
VIEWPMLM.EXE . . . . . . . . . . . . . . . . . . . . . . . . . 4
WHAT IS SIO . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Write Device Control Block (DCB) . . . . . . . . . . . . . . 16
Write Extended Mode Parameters . . . . . . . . . . . . . . . 19
