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56K Initialization strings

In order to use an initialization string for your modem, you must know what type of chipset it uses. If you do not know what type of chipset your modem uses, please see our modem diagnostic page.

Please choose the chipset type your modem uses from the choices below.

   My modem uses the Lucent chipset.
   My modem uses the Rockwell chipset.
   My modem uses the 3COM chipset.
   My modem uses the ESS, Cirrus, PCtel chipset.

Lucent Chipset

The following init strings can be used by Lucent Chipset modem users:

AT-V90=# where # can be any of the following to control the v90 downstream rate: 0 V.90 disabled

1 Auto Rate (default)
2-28,000               3-29,333               4-30,666
5-32,000               6-33,333               7-34666
8-36,000               9-37,333               10-38,666
11-40,000             12-41,333             13-42,666
14-44,000             15-45,333             16-46,666
17-48,000             18-49,333             19-50,666
20-52,000             21-53,333

ATS38=# where # disables or selects the KFlex downstream rate:

0 - disable KFlex (will force v90 -or- v.34 connection)
1 - Auto Rate (default)
2 - 32k             3 - 34k             4 - 36k             5 - 38k
6 - 40k             7 - 42k             8 - 44k             9 - 46k
10 - 48k           11- 50k           12 - 52k           13 - 54k

If you wanted to disable both K-56 Flex and V.90 to connect using the V.34 protocol, you would use the initialization string AT-V90=0 S38=0.

Rockwell Chipset

Rockwell has 2 different 56K chipsets on the market. The Rockwell Dual, and the Rockwell HCF / Soft56. The Dual chipset is used mostly by older Rockwell 56K modems and the HCF / Soft56 chipset is used mostly in newer Rockwell 56K modems.

The following init strings can be used by Rockwell chipset modem users:

NOTE: To make a Rockwell chipset modem report connect speed, not port speed, use the init string ATW2. (works for both the HCF and Dual modems. For Rockwell-based PCI modems, the command is ATMR=2.)

Rockwell Dual

For the Rockwell Dual modem, use the following strings:

AT+MS=12 - Disable K-56 Flex
AT+MS=56 - Disable V.90
AT+MS=11 - Disable both K-56 Flex and V.90

For example, to make a Rockwell Duel modem report the correct connect speed, and connect using the V.34 protocol, you would use: ATW2+MS=11

Rockwell HCF / Soft56

For the Rockwell HCF modem, use the following strings:

The +MS= command is used to select modulation, and limit connect speeds.

The format is: +MS=<modulation>,<automode>,<min tx rate>,<max tx rate>,<min rx rate>,<max rx rate> If any parameters are omitted, commas must be used.

To disable all 56K connections and connect at V.34, you would use: AT+MS=V34

To force V.90 use: AT+MS=V90,0

You can also limit the connection rate by specifying lower & upper limits as the 5th & 6th parameter:

AT+MS=V90,0,,,44000,52000 - will try to force a V.90 connection between 44k & 52k

For example, to make a Rockwell HCF/Soft 56 modem report the correct connect speed, and connect using the V.34 protocol, you would use: ATW2+MS=V34

3COM Chipset

The following init strings can be used by 3COM chipset modem users:

The commands: &Un and &Nn (n is a number between 0 and 39) control the connect speeds your modem will use. &U controls the lowest link speed, and &N controls the highest link speed.

Here are the possible values for n with a 3COM V.90 modem:

&Un - Lowest Link Speed
&Nn   n=0  Highest Link Speed
                
      n=1  300 bps         n=2  1200 bps       n=3  2400 bps
      n=4  4800 bps       n=5  7200 bps       n=6  9600 bps
      n=7  12000 bps     n=8  14400 bps     n=9  16800 bps
      n=10 19200 bps    n=11 21600 bps   n=12 24000 bps
      n=13 26400 bps    n=14 28800 bps   n=15 31200 bps
      n=16 33600 bps    n=17 28000 bps   n=18 29333 bps
      n=19 30666 bps    n=20 32000 bps   n=21 33333 bps
      n=22 34666 bps    n=23 36000 bps   n=24 37333 bps
      n=25 38666 bps    n=26 40000 bps   n=27 41333 bps
      n=28 42666 bps    n=29 44000 bps   n=30 45333 bps
      n=31 46666 bps    n=32 48000 bps   n=33 49333 bps
      n=34 50666 bps    n=35 52000 bps   n=36 53333 bps
      n=37 54666 bps    n=38 56000 bps   n=39 57333 bps

So, if you wanted to force a V.90 connection between 44,000 and 53,333 you would use the init string - AT&U29 &N36

You can also disable a V.90, or X2 connection with a 3COM chipset modem.

For the Sportster model, ATS32=34 will disable X2, ATS32=66 will disable V.90, and ATS32=98 will disable both X2 and V.90 resulting in a V.34 connection.

For the Courier model, ATS58=1 will disable X2, ATS58=32 will disable V.90, and ATS58=33 will disable both X2 and V.90 resulting in a V.34 connection.

ESS, Cirrus, PCtel Chipset

Unfortunately, we don't have any specific initialization strings for modems using the PCtel, ESS, or the Cirrus chipsets. You can try Modemhelp.org for more information relating to your modem.

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