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This chapter explains how to configure external modems to work with PortMaster products. For information on using the internal digital modems with the PortMaster 3, see Chapter 11, "Configuring the PortMaster 3."
This chapter discusses the following topics:
Ports S0 through S29 are asynchronous DTE ports with female RS-232 connectors. To connect these ports to a terminal or other DTE, use a null modem cable, typically male-to-female. Directions (input/output) are with respect to the PortMaster. The PortMaster does not use the Data Set Ready (DSR) signal.
Note ¯ 
When the console port is connected to a terminal, it uses software flow control and therefore requires pins 2, 3, and 7 only.
Null modem cables can be obtained from most suppliers of computer equipment.
Dial-up modems that operate over normal telephone lines at speeds of 28,800bps or higher are now available. These modems do not operate at a guaranteed throughput, but rather at a speed dependent on the quality of the line, the effectiveness of data compression, and other variables. These modems use hardware flow control to stop the data from the host by raising and lowering the Clear to Send (CTS) signal.
PortMaster products support hardware flow control using the RTS output signal and the CTS input signal, which is also used by the normal modem handshake.
Configure modems to do the following for use with the PortMaster:
PortMaster products use a modem table to automate the modem configuration process. The modem table is user-configurable and includes long and short modem names, preferred DTE rate, and the modem initialization string. For convenience, the table is preconfigured for many common modems.
When you specify the name of the modem and the attached port, the PortMaster automatically configures the modem for you, provided the modem is in the factory default state when it is initialized.
After a modem type has been specified, the PortMaster automatically sets the port for hardware flow control, the correct speed, and modem control when the port is reset.
To display the modems currently configured in your modem table, use the following command:
A modem table display looks like the following:
The modem type is either system or user. System indicates that the configuration settings are the factory default settings. User indicates that the user has configured the modem table settings for that modem.
To display the settings for a particular modem, use the following command:
The display for a modem looks like the following:
To add a modem to the modem table, use the following command:
For example, to add a Paradyne 3811+ modem to the modem table, enter
Note ¯ 
Use a \r for a carriage return, and a caret (^) to separate the send and expect characters in the string. In the example above, the PortMaster expects OK. Never use on or off for a modem short name.
Table 10-1 shows the current factory default settings for commonly used modems.
To automatically configure a modem and associate it in the modem table with the port it is attached to, use the following commands:
For example; to associate a U. S. Robotics V.34 modem with port S1 and configure the modem, enter
To configure all ports for the same modem type, use all instead of the port number in the previous example. After the modem is attached to the port, configure the other modem settings described in "Configuring Ports for Modem Use" on page 10-7.
To configure the modem not to answer when users dial in, set S0=0 in the initialization string.
The modem settings described in this section are configured for each port and should match the configuration on the attached modem.
The speed of a port is defined as the DTE baud rate. The PortMaster allows you to specify three different baud rates for each port and one baud rate for host device ports. Port speeds are sequentially matched from the first baud rate through the third baud rate.
For example, when a connection with this port is established, the PortMaster uses the first baud rate value to try to synchronize the connection speed. If no synchronization is possible, the PortMaster tries to synchronize speeds using the second baud rate value. If this fails, the third baud rate value is used. Each speed can be set between 300bps to 115200bps. The default speed is 9600bps.
Modern modems and terminals should always be set to run at a fixed rate. To define a fixed rate, lock the DTE rate by setting all three speeds to the same value.
To set the port speed, use the following command-entered on one line:
You can substitute any of the following for Speed:
You can set the speed for all the asynchronous ports simultaneously by using the set all speed command.
Set modem control on if you want to use the DCD signal for modem connections. When modem control is on, the PortMaster uses the condition of the carrier detect line to determine whether the line is in use. Modem control must be on for PortMaster outbound traffic. If modem control is off, the PortMaster assumes the carrier detect line is always asserted. As a result, the PortMaster cannot attach to the modem for outbound traffic because it regards the line as busy.
To set modem control, use the following command:
The parity setting must be configured to match the parity setting on the attached modem. The parity default value is none and must be used for ports configured for network dial-in or dial-out operation. Table 10-2 describes the parity options.
To set the parity for a modem and its port, use the following command:
The PortMaster supports both software flow control and hardware flow control. Software flow control uses the ASCII control characters DC1 and DC3 to communicate with the attached device and to start and stop the flow of data.
To set software flow control for a modem, use the following command:
Hardware flow control allows the PortMaster to receive data from the attached device by raising the Request to Send (RTS) signal on pin 4 of the RS-232 connector. The PortMaster sends information to the attached device only when the Clear to Send (CTS) modem line on pin 5 of the RS-232 connector is raised.
To set hardware flow control for a modem, use the following command:
Note ¯ 
Because it is more reliable, you should always use hardware flow control if it is available. Do not use both hardware and software flow control on the same port.
You can specify whether the DTR signal is dropped and the modem disconnected after a session is terminated. If line hangup is enabled and the session is terminated, DTR is held low, signaling the modem to disconnect. If line hangup is disabled, the DTR signal does not drop and the modem does not hang up when the user session terminates.
To set line hangup for a modem, use the following command:
Note ¯ 
Resetting the port administratively with the reset command always drops DTR.
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