Document # 122 Modem Help Guide to Diagnose Modem Problems
Last Updated: 1-17-98
Table of Contents
- Introduction (Please Read First)
- Common Modem Errors
- Possible Quick Fix- IGNORE DTR -for Windows 3.x and Macintosh
- Windows 95 Dialer and Dial-Up Networking Modem Help
- Changing Your Modem Strings (Default Modem commands)
- Verify your modem is not an RPI SW Error Correcting Modem
- Verify your Modem has the latest Firmware Updates
- UART Chip Information and how they effect External Modems
- How the Helpdesk Can Help Develop a Modem String
- Related Documents and Contact Information
This guide is designed to help you track down possible problems with
your modem. A modem is the central and most important part of any dial
connection. Modems come in a wide variety of performance levels and
price ranges. A good hardware error correcting modem with updated
firmware will usually give a solid and stable connection.
The other two important components of your dial connection are your
software/operating system and phone line. The Software/operating system
is another key component because it controls your modem. Make sure you
have the help document for troubleshooting your dial software. There
is an available guide for troubleshooting phone lines as well.
- Modem does not Initialize (does not give an OK when commands are sent)
- Modem gives an endless or long handshake when connecting
- Dropped Connections and overall bad connection performance
- Getting the error message "Your Modem or TCPIP configuration may be in
Error the first and second configuration servers are unavailable"
If you are using Windows 3.x or a Macintosh machine you can try
enabling IGNORE DTR or appending the modem command &D0. This can be
used anytime a connection fails after an attempted handshake. With
Ignore DTR you may have a problem getting your modem to disconnect. If
so, try adding S10=200 or S25=200 to the end of the second command string
without enabling Ignore DTR. To add this use Create in the Modem Settings
Page. One of these S commands should be recognized by the modem and one
will not. If this fails go to the next sections.
Modems must be installed in Windows 95 inside the Modems Control Panel.
Dial-Up Networking (DUN) is the built in Win 95 dialer and it uses this
modem installation. Our Win 95/NT dialer is an interface over DUN so it
uses this modem installation as well. Note that Windows 3.x (or 16-bit)
dialers still work in Windows 95, but they initialize the modem apart
from Win 95. If using our Win 3.x dialer in Win 95 follow the fixes
for Win 3.x. It is not usually necessary to modify modem commands in
Win 95 (to append to your Win 95 modem string go to Control Panel,
Modems, highlight your modem, click Properties, Connection tab and
click Advanced. Add commands to Extra settings without adding an AT).
If you are having connection problems (i.e. disconnecting) try lowering
your modem settings as follows:
- Click My Computer, then DUN. Right click the AT&T Global Network Icon
and choose Properties. Choose Configure and drop the Maximum Speed to
19,200 and click the Connection Tab and choose Port Settings. Uncheck
Use FIFO Buffers after lowering the Receive and Transmit Buffers. Retry
your connection. If you can connect or your modem no longer drops try
slowly increasing these settings to find your maximum performance.
You should also verify you have the following:
- Click the Advanced from the connection tab and verify Use error control,
Compress data, Use flow control and Hardware (RTS/CTS) are checked.
- Download the latest modem drivers from your manufacturer.
If these procedures fail see the section on Software Error Correction,
Firmware updates, and UART information.
Before trying these modem strings be sure and try some of the modems
already listed in your software i.e. Hayes Compatible, Default, Other,
and Hayes modems etc. Also make sure you have the latest modem list
in your Software (see related documents). Also verify your modem cables
are secure and the com port is correct.
To change the modem commands in the software itself simply go to your
Modem Settings page. You will either see fields to type in new modem
commands or you will see your modem name. Use the Create button in the
modem settings page to add these strings.
NOTE: If your software only has a field for one Modem command you can
combine the 2 strings into one i.e. the Default command would be:
Default AT&F AT&D2&C1X4V1Q0S7=70 should be AT&F&D2&C1X4V1Q0S7=70
These strings are also listed in the MODEM.LST file on the FTP site
and should be in the latest software. So if you have already tried these
default modem types skip to the Secondary Default strings below.
MODEM TYPE 1ST (Initialize) 2ND COMMAND MODEM STRING (Originate)
Default AT&F AT&D2&C1X4V1Q0S7=70
Default Type 10 AT&F AT&D2&C1X4V1Q0S7=70W2\N3&K3
Default Type 20 AT&F AT&D2&C1X4V1Q0S7=70\N3&K3
Default Type 30 AT&F AT&D2&C1X4V1Q0S7=70\G0\N3\Q3
Default Type 35 AT&F AT&D2&C1X4V1Q0S7=70\N3\Q3\J0
Default Type 50 AT&F AT&D2&C1X4V1Q0S7=70\N3\Q3
Default Type 60 AT&F AT&D2&C1X4V1Q0S7=70W2\G0&Q5&K3\J0
Default Type 64 AT&F AT&D2&C1X4V1Q0S7=70W2&Q5&K3\J0
Default Type 66 AT&F AT&D2&C1X4V1Q0S7=70&Q5&K3\J0
Default Type 70 AT&F AT&D2&C1X4V1Q0S7=70&Q5&K3
Default Type 80 AT&F AT&D2&C1X4V1Q0S7=70&M4&H1&B1
Note: You can also try changing the &D2 to &D0 in the above commands.
Especially if using WIN 3.x or Macintosh Systems.
The following are other strings that can be used. These strings only
use one command modem string instead of two so leave the 2nd field blank,
add the same string again or add AT. These are not in the modem.lst file.
Secondary Default strings
DEFAULT 1 AT&F
DEFAULT 2 AT&F1
DEFAULT 3 AT&F2
DEFAULT 4 AT&F0
If these procedures fail see the section on Software Error Correction and
Firmware updates.
If your modem has an RPI chipset and it is a Class 1 modem, it does
not support hardware error correction. Error Correction is the feature
in high speed modems that allow it to compensate for changes in line
conditions. The modem will actually decrease and increase its
connection speed depending on the current line conditions. Hardware
error correction is when the modem itself regulates the error correction.
Software error correction is where the modem has to rely on the
computer processor to perform the error correction. Software error
correction can cause long delays which usually ends in a disconnection.
Since our service requires hardware error correction these modems are
unreliable at the very best. The best way to find out if you have a
software error correcting modem is to call your modem manufacturer and
ask them if your modem model is software error correcting. If you
verify your modem is hardware error correcting you should check for the
latest version of error correction (firmware- listed below).
Most Hardware Error correcting modems offer Firmware Updates meaning
the modem can be upgraded without having to purchase a new modem. There
are two different kinds of Firmware upgrades:
- EPROM (Erasable Programmable Read Only Memory)
An actual chip is sent from the modem manufacturer to replace the
existing chip. This is usually done for a small fee unless there is
a known bug with your firmware revision (which is the case most of
the time). Make sure you tell them you are having problems.
- FLASH Upgrades
These are basically software upgrades that are burned into the modem.
They are usually free and offered off the Modem Manufacturer's Home
Page or BBS.
Firmware updates can sometimes increase your baud rate but most
importantly it updates the Error Correction. Error Correction is
negotiated during the modem handshake and if the modem has bad Error
Correction you may receive Endless Handshaking. Other problems can
include frequent disconnections and low connection speeds (note most of
time low connect speeds are related to phone lines so obtain the V34 or
x2 guides). Make sure you also obtain your software package help guide
and try a different access gateway to verify the problem is not a local
problem. Many models of Megahertz, IBM MWave and USR modems are known
for needing firmware updates. Contact your manufacturer for details.
Some connection errors are caused by a downlevel version of an interface
chip called the Universal Asynchronous Receiver Transmitter (UART).
It can be found on your computer com port or on your internal modem.
The latest level of this chip provides the role of a 'traffic cop'
and buffers the incoming data from the modem for the PC to process.
Versions of UARTs include: 8250, 16450, 16550, and 16550a. You should
have a 16550a UART for 14.4 modems and higher. To update your UART you
may purchase an internal modem with a built in UART or obtain an I/O
serial card with a 16550a UART for external modems. Otherwise lower the
modem speed to 9600.
Do the following to determine what UART level you are using:
- In Windows 95 go to the Modems icon in Control Panel. Click the tab
Diagnostics and highlight your modem name. Click the button More
Info... (while not dialed in) and the UART type will be displayed.
- In Windows 3.x exit Windows and go into a DOS mode (it is important
to run this in Dos and not a Dos Window). Type the command MSD at the
Dos prompt, choose the option Com Ports and read the UART chip type at
the bottom of the Window.
- In OS/2 Warp type MODE COMx (where x is the com port) in an OS/2
Window. If the BUFFER field is AUTO you have a 16550 UART.
If your modem is NOT software error correcting and you were unable to
get connected please contact the helpdesk and we can help develop a modem
command for your modem IF you have your manual. Obtain an incident
number and fax us the AT and S-register commands from your modem manual.
Attention the fax to Judson Bach placing your account and incident number
next to the number. Also give us the exact modem manufacturer and model
number. Please fax this information to the number 1-813-878-6693 and
modem development will determine a modem string to use.
Related Documents that may Assist you:
- Document # 126 56K Modem Technology
- Document # 125 V.34 Modem Protocol Information
- Document # 101 OS/2 Warp Dialer Help guide
- Document # 102 Windows 3.x Dialer Help guide
- Document # 103 Windows 95 Dialer Help guide
- Document # 104 Macintosh Dialer Help guide
- Document # 120 Line Noise Help guide
- Document # 121 Modem Listing Document
Additional Contacts:
- Your Internet Helpdesk is your Network Support.
- Your Modem Manufacturer is your Modem Support.