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Chapter 5 – AT Commands, S-Registers, and Result Codes
Multi-Tech Systems, Inc. SocketModem MT5600SMI Developer’s Guide 60
Data Compression Commands
This section contains parameters to condition modem use of standard ITU-T V.42bis Data Compression
Procedures.
Command: +DS Data Compression
Description: This extended-format compound parameter controls the V.42bis data
compression function if provided in the modem. It accepts four numeric
subparameters:
Defined Values: <direction> Specifies the desired direction(s) of operation of the data
compression function; from the DTE point of view.
+DS0 Negotiated; no compression (V.42bis P0=0).
+DS3 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.
+DS0 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 code word 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).
Report Commands: +DS? Reports Current or Selected Values.
Response: +DS:
<direction>,<compr_neg>,<max_dict>,<max_string>
Example: +DS:
3,0,2048,32 for the defaults and 2048 entry max dictionary.
+DS=? Reports Supported Range of Parameter Values.
Response: +DS:
(<direction> range),(< compr_neg > range),
(<max_dict> range),(<max_string> range)
Example: +DS: (0,3),(0),(2048),(32)
Command: +DS44 V.44 Compression Select
Description: This extended-format compound parameter controls the V.44 data
compression function.
Defined Values: <direction> Decimal number that specifies the desired direction(s) of
operation of the data compression function; from the DTE point of view.
+DS440 Negotiated, no compression.
+DS441 Transmit only.
+DS442 Receive only.
+DS443 Both directions, accept any direction. (Default.)
<compress_negotiation> Decimal number that specifies whether or not
the modem should continue to operate if the desired result is not obtained.
+DS440 Do not disconnect if V.44 is not negotiated by the remote
DCE as specified in <direction>. (Default.)
+DS441 Disconnect if V.44 is not negotiated by the remote DCE
as specified in <direction>.
<capability> Decimal number that specifies the use of stream method,
packet method, multi-packet method.
+DS440 Stream method. (Default.)
+DS441 Packet method.
+DS442 Multi-packet method.