MODEM TROUBLESHOOTING
AND SUPPORT MANUAL
VERSION 1.1
Compiled By:
Chris Hill
TECHNICAL SUPPORT
DATE: 14-10-2002
With thanks to Level 2 iPrimus Support
1. How Does a Modem Work?
These are basically the steps a computer talking to another computer uses (Both computers have a modem attached to them)
The modem on one PC will dial the other modem. Immediately after answering the call from the other modem, the receiving modem will put a tone on the line, and recognize it as being a modem. Let’s face it- We can’t make that tone, so the computer will automatically assume this is a modem answering the line.
This initial tone, called the Guard Tone, is followed by a transmission from the receiving modem called an Unmodulated Carrier. This is a set tone, of a certain frequency. Depending on the speed if the modem, this tome will have a different pitch to the guard tone. If the calling modem recognizes the pitch, it will start sending a Carrier Tone. Both modems need this tone. This tone will stay up throughout the modem connection. If the carrier tone disappears, so does the connection <ie-disconnection> This is why most ext modems have a CD, or Carrier Detect light on them, for when there is a carrier detected on the other end.
Now that the Carrier Detect light is on, the two modems agree to talk on a certain carrier frequency pair. Then they are ready to start ‘talking’, or sending and receiving data. However, the receiving modem will need to know when to start listening for data. This is where a UART chip comes in. This chip adds some data to the data you want to send. Because of this, a notifier to let the modems know we will start sending data. One bit is sent, called a Start Bit. Then on come all the data bits we want to send. When we are done sending, one more bit, called a Stop bit, is sent. The modem on the other end has a UART as well, and this will strip off the start and stop bits, so it looks exactly the same as when you put it in (sent).
OK…all of that is basically how a modem sends digital data over an analogue line. Now we focus on the errors that sometimes occur in sending and receiving….
2. Modem Errors
Modems continuously monitor the status of the lines they are on, the quality of the signals they get, the number of errors they correct and the validity of the data on each of the carriers. When the modems see excessive problems, they ask for a re-evaluation of the phone line. This is done by interrupting the data flow and sending a low burst tone over the line. Once that is done, the handshaking and sending of carriers can continue. This is basically called retraining, and can occur at any time. This uses only a very small amount of carriers, and normally works. This is called Automatic Fall Back. After a while, if it sees more errors, it will retrain again, using a few more carriers. If all is successful, speed is brought back up to normal- for each fall back results in a drop of modem speed. This process is called Fall Forward. These Fall Forward/Back sequences are controlled by both modems and their lines. Poor quality lines will result in a disconnection, rather than a huge retrain.
3. Modem Diagnostics
Modem diagnostics are very important in troubleshooting. Modem drivers can be ascertained from this, as well as other information that can give you knowledge of the problem. ATI commands are taken out of the diagnostics program, and can be split into the following responses:
Win9x and ME-Start>Settings>Control Panel>Modems>Diagnostics tab. Highlight the COM port and click More Info.
Win2k/XP-Start>Settings>Control Panel>Phone and Modems>Click the Modems tab, click Properties, then click Diagnostics. You will see a “Query Modem” button. Click this. The port is automatically selected.
Win NT-Start>Find>Files or Folders. Look for a file named modemdet.txt or modemdet.log
ATI3: Firmware revision information.
ATI4: OEM defined identifier string in either ASCII format, or Hayes binary format.
ATI5: Country Code
ATI6: Data pump modem & internal code revision.
The most common ATI’s you will need to get for modem problems are ATI3, 4 & 6
4. What is the difference between an internal and external modem?
A hardware (or “real”) modem has a controller and interfaces to a PC that outputs serial data through a COM port on a PC. The modem hardware then processes this data and converts this to analog for the phone line. The majority of this in an internal modem (or software modem) is done by the CPU and the resulting data is transferred through the modem card in a virtual COM port. These modems do not use a COM port, but since all modem application software is designed to use a COM port, the modem driver emulates a physical port (tricking the OS in the process) so that communications software applications will work (ie- Dial-Up Networking).
The LT WinModem is also known as “Apollo” or “Mars”. (Lucent uses Apollo to refer to the ISA-bus version and Mars for the PCI-bus version.)
http://808hi.com/56k/ltwin.htm for any information.
ATI3- LT v90 Data+Fax+Voice Modem Version 5.65
ATI4- 72
ATI5- 5.65,0,01,11C1,0440
ATI6- OK
Anything above V. 5.43 is known as Lucent WinModem
Anything lower is known as LTWin.
Below and including V 5.18 is k56 Flex
Version 5.49 and above. Older revisions may need a string to establish connection. <Use strings at your own risk!!>
Latest Revision- Ver. 5.65 (although 5.92 is out, but is still in testing!!!!!)
Lucent Clones
· Netcomm IN5692
· Mitsubishi Diamond Voice (PM560LHI)
· Genius GM56PCI-L
· Multitech Systems MT5634ZPW-PCI
Rockwell/Conexant
Rockwell, now Conexant, doesn’t make modems- they make chipsets and develop the firmware/drivers and sell them to various manufacturers eg- Compaq, IBM. So these modems are normally found in brand name PC’s. If these PC’s are under warranty, we DO NOT TOUCH THEM.
The “HCF” chipset is actually a single-chip PCI software modem. There is a variation of the HCF chipset that includes sound card and modem functions (Used by HP) known as RTAD. Also known as “Riptide”, the modem portion of this product can’t be upgraded with the same drivers as modem only HP products. Riptide 2.2.2.xxx modems are current in HP machines, and are still being tested.
http://808hi.com/56k/rockhcf.htm for more information.
ATI3- 2.1.2.161.000
ATI4- This can differ amongst OEM’s
ATI6- DP Rev BA
Variants:
PCI Data fax (Not common)
PCI Data Fax Speakerphone (Most common, requires upgrades constantly) Used in example ATI
PCI Data Fax RTAD (This is starting to become more common) Will need an upgrade. Refer to upgrades page. (http://support.iprimus.com.au)
2.x.x.135 < = Rockwell
2.x.x.154 > = Conexant
V90
Should be fine with version 2.1.2.161.xxx >
Latest Revision- 2.1.2.161.000 (although 2.1.2.164.005 is out and in testing)
HCF Clones
· Aztech Labs MDP-3858 2.1.2.136 (Packard Bell)
· Diamond/Supra Express 56i Pro 2.1.2.156
· Acer HCF Speakerphone 2.1.2.110
SoftK56
The Rockwell/Conexant SoftK56 (also referred to an HSF) is a HSP- Host Signal Processor- modem. This type of modem is the worst kind- all modem functions are carried out by your PC. Variants and naming conventions are as for HCF.
http://808hi.com/56k/rockhcf.htm for more information.
ATI3- SoftK56V_B2.1_V2.11.06.02
ATI6- Cmodem Version 11
RkSample Version 340
Earlier Versions
ATI3- SoftK45V_B2.1_v2.05
ATI3- SoftK56V_B2.1_V2.08.02
V90
Most ISP's show stability with version 2.11.06, although 2.08.02 should still keep users happy.
Latest Revision- V2.12.10
SoftK56 Clones
· Aztech Labs MSP-3880 (Packard Bell)
Motorola SM56
The SM56 PCI Software Modem is a Host Signal Processing (HSP) based modem with both controller and data pump functions running from the CPU.
www.motorola.com/networking/products/sm56_pci_software_modem/index.html
ATI3- Release 3.02 AD04 Build 671
V90
Most ISP's show stability with Build 805. Previous builds are, to say the least, junk!
Latest Revision- Build 805
No Clones for this modem as of this current time.
USR 3Com Sporster 33.6K WinModem
This software modems have been extremely problematic. There are a few variants and models. The current working string for these modems to establish a connection is at&f1s32=34
PCTEL HSP Audio modem Riser (AMR)
HSP MicroModem 56 & Variants (MR2800)
These modems, to again say the least, are absolute junk (Please do not tell the customer this!!). CPU usage rates 75%+ and the manufacturer support is almost non-existent. It will probably need a string to operate at a patchy/workable level.
www.pctel.com/consumer_faq.htm
AMR
Latest Revision for the AMR is 7.64. The only problem is finding it. There is no known site for this upgrade!
ATI3- PCTEL 7.55 MS
ATI4- PCTEL Data/Fax/Voice/Speakerphone
HAMR
ATI1- HAMR 56000 Voice Modem
Modem Vendor
Version 2.75c
ATI2- SWVendor
Ver2.75C
MV (CID)
ATI3- HWVendor
SIL-22(Sec) on ICH 82801A
MR2800 (Packard Bell)
ATI1- MR2800 Data Fax Modem
AZT
Ver2.60.00PB
ATI2- SMARTLINK
Ver2.60.00PB
MO
ATI3- AZT
SIL-22(Pri) on ICH0 82801 AB
ATI7- Country: AUSTRALIA
Serial Number: 98638029
Protocol Factor: 96c38a8
HARDWARE MODEMS
Internal/External 28.8/33.6K Modems
Majority are Rockwell based chipsets. Examples: Simplemodem 288, Dynalink 1433VQE
28.8K
ATI3- v1.510-v34_DS
ATI4- 2814SAM for Australia
ATI6- RC288Dpo Rev 05BA
33.6K
ATI3- V1.977C-v23_ACF_DS1_S5
ATI6- RCV336 DPFSP Rev 44BC
Both 05BA and 44BC modems are quite finicky. Put simply- they will either not work, or they will. There is no in between. Use of commas after the dialin number have proven successful.
External RCV56DPF Modems
Netcomm Roadster II 56 Ultra PNP (AM5692)
ATI3- 2.300-v90_2M_DLS
ATI4- Netcomm Roadster II 56 v90 2.300SA
ATI6- RCV56DPF-PLL L8571a Rev 36.00/36.00
There are two generations of data pumps used in the Netcomm external modems, the L8570a and the L8571a
L8570A – 1st Generation Data Pump
Can be flashed to v90. Planet network is still in testing at Flex, however.
Chipsets
K56Flex ONLY
Last chipset for k56 Flex is 1.200
Data Pump
K56Flex
Up to Revision 45.0/45.0
V90 – Latest
Firmware Revision: 2.200
Data Pump Revision: 47.32 (v90 ONLY!)
L8571A – 2nd Generation Data Pump
Are capable of flash upgrades, but these are v90 straight out of the box, so there is really no need to.
Netcomm only offer upgrades on a few models.
Earliest Example: Swannsmart/WebExcel/KTX
Firmware Revision for Chipset: 2.200
Data Pump Revision: 19.00
Latest Example: Banksia, later model Netcomms.
Firmware Revision for Chipset: 2.310
Data Pump revision: 36.00
External Cirrus Logic/Ambient (MD56xx) Modems
Not known for stability. Patchy at best. A lot of these modems are on product recall!
Auslinx ABC v90 Modem
ATI1- CD04.08-604C.3 SERIAL(V.90 ONLY)
ATI2- ROM Test OK
ATI3- CL-MD56xx
ATI4- Cirrus Logic Inc. Modem Engine
ATI6- AUS1
External 3Com/USR Modems & Clones
USR 56K Sportster Flash
ATI3- US Robotics Sportster Flash 56000 Rev 10.1.31
ATI4- US Robotics Sportster Flash 56000 rev 10.1.31 settings
ATI6- The US Robotics Sporster 56000 Link Diagnostics
(and after that, a table of diagnostics appear which is not too important)
Driver support can be difficult at times. Older USR’s need a specific string to disable x2 (A lovely modem protocol which isn't supported by many Australian ISP's) The best string to disable this is at&f1s32=s34
PCMCIA / PC CARD MODEMS
These modems are actually hardware based modems. Examples include: Xircom, 3Com Megahertz and Banksia. They are all rather line dependant. No real problems at the moment, however unattenuated signal strings are being researched into.