Chapter 4 - V.22bis Commands
Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide
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V.22bis Synchronous Access Mode
Commands
Three commands support Synchronous Access Mode:
+ES enables and disables Synchronous Access Mode in the client or central site modem. Enabling Synchronous
Access Mode enables the use of the 8-bit command characters of the Draft ITU-T Recommendation V.80 (See
the table under the +IBC command - Data Communication over the Telephone Network. In-Band DCE Control
Command).
+ESA configures the operation of the Synchronous Access Submode
+ITF selects Transmit Flow Control Thresholds
+ESA Configure Synchronous Access Submode
The operation of the Synchronous Access sub-Mode is configured by the +ESA parameter
..
This extended-format compound parameter is used to control the manner of operation of the Synchronous Access
Mode in the modem. It accepts six numeric subparameters:
Syntax
+ESA=[<trans_idle>[,<framed_idle>[,<framed_un_ov>[,<hd_auto>[,<crc_type>[,<nrzi_en>[,<syn1>[,<syn2>]]]]]]]]
Defined Values
<trans_idle>
Specifies the bit sequence transmitted by the modem when a transmit data buffer under run
condition occurs, while operating in Transparent sub-Mode. The options are:
0 In Transparent sub-Mode, modem transmits 8-bit SYN sequence on idle. Modem receiver
does not hunt for synchronization sequence (default and fixed).
<framed_idle>
Specifies the bit sequence transmitted by the modem when a transmit data buffer under run
condition occurs immediately after a flag, while operating in Framed sub-Mode. The options are:
0 In Framed sub-Mode, modem transmits HDLC flags on idle (default and fixed).
<framed_un_ov> Specifies the actions undertaken by the modem when a transmit data buffer under run or overrun
condition occurs immediately after a non-flag octet, while operating in Framed sub-Mode.
0 In Framed sub-Mode, modem transmits abort on under run in middle of frame (default).
1 In Framed sub-Mode, DCE transmits a flag on under run in middle of frame, and notifies
DTE of under run or over run.
<hd_auto>
This subparameter should not be commanded.
<crc_type>
Specifies the CRC polynomial used while operating in Framed sub-Mode. The options are:
0 CRC generation and checking disabled (default).
1 In Framed sub-Mode, the 16-bit CRC is generated by the modem in the transmit direction,
and checked by the modem in the receive direction.
<nrzi_en>
Specifies if Non Return to Zero Inverted (NRZI) encoding is to be used by the modem for transmit
and receive data. The options are:
0 NZRI encoding and decoding disabled (default and fixed).
<syn1>, <syn2> Specifies the octet value(s) to be used while performing character-oriented framing. <syn1> is to be
commanded to 255 (FFh); <syn2> is not to be commanded.
Reporting Selected Options
The modem reports the selected options in response to the following command:
+ESA?
The response is:
+ESA:
<trans_idle>,<framed_idle>,<framed_un_ov>,<hd_auto>,<crc_type>,<nrzi_en>,<syn1>,<syn2>
Example:
+ESA?
+ESA: 0,0,0, ,0,0,255, For the defaults.
Reporting Supported Options
The modem reports the supported options in response to the following command:
+ESA=?
The response is:
+ESA: (list of supported <trans_idle> values), (list of supported <framed_idle>values),(list of supported
<framed_un_ov> values), (list of supported <hd_auto>values),(list of supported <crc_type> values), (list of supported
<nrzi_en> values),(list of supported <syn1> values), (list of supported <syn2> values)
Example:
+ESA=?
+ESA: (0),(0),(0-1), ,(0-1),(0),(255),
