Compaq 281862-002 manual Data Terminal Ready DTR Interpretation, Flow Control, Error Correction

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Data Terminal Ready (DTR) Interpretation

Most modems have a configuration option that controls the interpretation of the DTR serial port interface signal. For IRC to function properly, the modem must be configured to terminate a connection whenever DTR is dropped. Improper setting of this configuration option results in the improper termination of an existing IRC session and may result in the inability to establish a future IRC connection. The &D AT command controls this setting in most modems. Since modem vendors differ with respect to the default setting of this configuration option, appending an &D2 to Integrated Remote Console’s initialization string insures proper DTR interpretation.

Flow Control

IRC is designed to use hardware flow control on the serial port interface. For IRC to function properly, the modem must be set to hardware flow control for both receive and transmit operations. Improper setting of this configuration option could result in the loss of characters, causing the remote terminal to display incomplete or garbled information. Modem manufacturers differ with respect to how this configuration option is implemented and controlled. Typical AT commands to configure flow control include &K, &H, &R, &J, &E, \G or \Q. Refer to your modem’s AT command reference for more details.

Error Correction

Most high-speed modems, by default, automatically negotiate an error control protocol such as v.42 (LAPM) or MNP upon establishing a connection to another modem. For connection speeds in excess of 1200 baud, error control is essential to insure proper communication between IRC and the management console. If error control is not negotiated between modems, erroneous data may result in either the inability to obtain a login prompt, garbled characters on the terminal display, or incorrect or extra keystrokes being sent to the server. Error control is normally negotiated, unless it is explicitly turned off on either modem or the modems are incompatible. If you encounter any of the problems mentioned above, try using identical modems for both the server and the management console. Typical AT commands to configure error control include \N, &Q, &M, &E, and S-Registersettings. Refer to your modem’s AT command reference for more details.

Compaq Integrated Remote Console User Guide