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Chapter 2 – AT Commands
Multi-Tech Systems, Inc. AT Commands Reference Guide (S000273F) 20
Data Compression Commands
Command: +DR Data Compression Reporting
Values: 0, 1
Default: 1
Description: 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).
+DR0 Data compression reporting disabled (no +DR result code transmitted).
+DR1 Data compression reporting enabled (+DR result code transmitted). (Default.)
+DR: <type> 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).
Report Commands: +DR? Reports current or selected values.
+DR=? Reports supported range of parameter values.
Command: +DS Data Compression
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).
<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 maximum number of dictionary entries (2048 entries) that should
be negotiated (may be used by the DTE to limit the code word size
transmitted, based on its knowledge of the data to be transmitted).
<max_string> Specifies max string length (32 bytes) to be negotiated (V.42bis P2).
Default: 3
Description: This extended-format compound parameter controls the V.42bis data compression
function if provided in the modem. It accepts four numeric subparameters:
+DS=[<direction>[,<compr_neg>[,<max_dict>[,<max_string>]]]]
Report Commands: +DS? Reports current or selected values.
+DS=? Reports supported range of parameter values.
Command: +DS44 V.44 Compression Select
Description: This extended-format compound parameter controls V.44 data compression function.
Values: <direction> The decimal number that specifies the desired direction(s) of operation of
the data compression function; from the DTE point of view.
0 Negotiated, no compression.
1 Transmit only.
2 Receive only.
3 Both directions, accept any direction. Default
<compress_negotiation> The decimal number that specifies whether or not the modem
should continue to operate if the desired result is not obtained.
0 Do not disconnect if V.44 is not negotiated by the remote DCE as
specified in <direction>. Default
1 Disconnect if V.44 is not negotiated by remote DCE as specified in
<direction>.
<capability> The decimal number that specifies the use of stream method, packet
method, multi-packet method.
0 Stream method. Default
1 Packet method.
2 Multi-packet method.