Multi-Tech Systems MT2456SMI22 22bis Synchronous Access Mode Commands, Reporting Selected Options

Chapter 4 - V.22bis Commands

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:

0In 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.

0In Framed sub-Mode, modem transmits abort on under run in middle of frame (default).

1In 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:

0CRC generation and checking disabled (default).

1In 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),

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 31