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Welcome to 56K Information Access

Product Features

Installation for All Operating Systems

Troubleshooting

Technical Reference >

Introduction to Syntax and Procedures

Data Command Set

• Generic Modem Commands
• DTE Interface
• Call Control
• Modulation Control Commands
• Error Control Commands
• Data Compression Commands
• Diagnostic Commands
• V.92 +P Commands
• S Parameters

Result Codes

Glossary

Regulatory Information

Limited Warranty

Data Compression Commands

This section contains parameters to condition modem use of standard ITU-T V.42bis Data Compression Procedures.

+DS - Data Compression

This extended-format compound parameter controls the V.42bis data compression function if provided in the modem. It accepts four numeric subparameters:

Syntax

+DS=[<direction>[,<compr_neg>[,<max_dict>[,<max_string>]]]]

Defined Values

<direction> Specifies the desired direction(s) of operation of the data compression function; from the DTE point of view.

0 - Negotiated; no compression (V.42bis P0=0).
3 - both directions, accept any direction (V.42bis P0=11). (Default.)

<compr_neg> Specifies whether or not the modem should continue to operate if the desired result is not obtained.

0 - Do not disconnect if V.42bis is not negotiated by the remote modem as specified in <direction>.

<max_dict> Specifies the maximum number of dictionary entries (2048 entries) which should be negotiated (may be used by the DTE to limit the codeword size transmitted, based on its knowledge of the nature of the data to be transmitted).

<max_string> Specifies the maximum string length (32 bytes) to be negotiated (V.42bis P2).

Reporting Current or Selected Values

Command: +DS?
Response: +DS: <direction>,<compr_neg>,<max_dict>,<max_string>
Example: +DS: 3,0,2048,32 for the defaults and 2048 entry max dictionary.

Reporting Supported Range of Parameter Values

Command: +DS=?
Response: +DS: (<direction> range),(< compr_neg > range), ( <max_dict>range),(<max_string> range)
Example: +DS: (0,3),(0),(2048),(32)

+DR - Data Compression Reporting

This extended-format numeric parameter controls whether or not the extended-format +DR: intermediate result code is transmitted from the modem to the DTE.

S95 bit 5 is reset to 0 for +DR=0 and is set to a 1 for +DR=1. The more recent setting of +DR or S95 bit 5, and the W command setting, determines the actual data compression result code reporting (see S95 Parameter and W Command).

Syntax

+DR=[<value>]

Defined Values

<value> decimal number corresponding to the selected option:

Reporting Current or Selected Values

Command: +DR?
Response: +DR:<current value>
Example: +DR: 1 For the default setting.

Reporting Supported Range of Parameter Values

Command: +DR=?
Response: +DR: ( <value> range)
Example: +DR: (0,1)

+DR: Intermediate Result Code

The +DR: <type> reported represents the current (negotiated or renegotiated) modem-modem data compression type. If enabled, the intermediate result code is transmitted at the point after error control negotiation (handshaking) at which the modem has determined which data compression technique will be used (if any) and the direction of operation. The +DR intermediate result code, if enabled, is issued after the Error Control Report (+ER) and before the final result code (e.g., CONNECT).

The format of this result code is:

Result Code Syntax

+DR: <type>

Defined Values

<type> An alphanumeric code corresponding to the selected option:

NONE - Data compression is not in use.
V42B - V.42bis is in use in both directions.
V42B RD - V.42 bis is in use in receive direction only
V42B TD - V.42 bis is in use in transmit direction only
V44 - V.44 is in use in both directions
V44 RD - V.44 is in use in receive direction only
V44 TD - V.44 is in use in transmit direction only
ALT - MNP 5 compression.

Example +DR: V42B

%C - Enable/Disable Data Compression

Enables or disables data compression negotiation. The modem can only perform data compression on an error corrected link. The parameter value, if valid, is written to S41 bits 0 and 1.

Syntax

%C<value>

Defined Values

<value> Decimal number corresponding to the selected option.

Result Codes