Multi-Tech Systems MT2456SMI22 manual Transmit Flow Control Thresholds, +Itf?

Chapter 4 - V.22bis Commands

+ITF Transmit Flow Control Thresholds

The +ITF command determines the flow control thresholds used by the modem for transmit data from the DTE. This optional compound parameter allows the DTE to determine the input buffer size in the modem for data on circuit 103 (transmit data) from the DTE, to control the thresholds used for flow control of such data, and to control how often the modem reports to the DTE the number of octets in this buffer. The DTE can adjust its own thresholds for flow control of data on circuit 104 (received data) from the modem.

Syntax +ITF=[<off>[,<on>[,<report_period>]]]

Defined Values

<off> Determines the threshold, in octets, above which the modem will generate a flow off signal. Applicable in Synchronous Access and Frame Tunneling modes. Default <off> value is 255.

For the <on> and <off> subparameters, the input buffer is assumed to reside between the modem’s V.24 interface and the Synchronous Access protocol layer; i.e., the buffer count includes all octets, including EM codes, received from the DTE, with the exception of DC1 and DC3 if these are used to signal <modem-by- DTE> flow control.

The modem returns the ERROR result code if the DTE specifies that the <off> subparameter be set to a value less than or equal to the <on> subparameter; in this case, the current parameter value settings are not modified.

<on> Determines the threshold, in octets, below which the modem will generate a flow on signal. Applicable in Synchronous Access and Frame-Tunneling modes. Default <on> value is 64.

<report_period> Not supported. A fixed value of zero is used and reported.

Reporting Selected Options

The modem sends a string of information text to the DTE consisting of selected options in response to the following command:

+ITF?

The response is:

+ITF: <off>,<on>,<report_period> Example:

+ITF?

+ITF: 255,64,0 Default values

Reporting Supported Options

The modem sends a string of information text to the DTE consisting of supported options in response to the following command:

+ITF=?

The response is:

+ITF: (list of supported <off> values),(list of supported <on> values),(list of supported <report_period> values) Example:

+ITF=?

+ITF: (0-255),( 0-255),(0)

The maximum reported <off> value is the input transmit data buffer level at which the modem signals a transmit data overrun indication to the DTE.

Multi-Tech Systems, Inc. MT2456SMI-22 SocketModem Developer’s Guide 32