Setting Half-Duplex Mode - Cisco 2500 Series Installation And Configuration Manual

Configuring the Router

Setting Half-Duplex Mode

Low-speed serial ports that are set as DCE can be set to use either controlled carrier mode or constant carrier
mode.
Controlled carrier mode sets the interface to deactivate DCD until a transmission is sent to the interface. DCD
is then activated, and the interface waits an amount of time you configure, and then transmits the data. After
the transmission, the interface waits for a period of time and then deactivates DCD.
Constant carrier mode (the default for low-speed interfaces) activates DCD at all times.
Take the following steps to enable controlled carrier mode:
Step 1 Connect a terminal by following the instructions in the section
Modem" in the chapter
Step 2 Enter the config terminal command at the enable prompt to enter configuration mode:
Router# config terminal
You can now make changes to the configuration. Press Ctrl-Z to exit configuration mode.
Step 3 Enter the half-duplex command to reset the port from constant carrier mode to controlled carrier
mode:
interface serial 2
half-duplex controlled carrier
Step 4 Enter the no half-duplex command to return to constant carrier mode:
interface serial 2
no half-duplex controlled carrier
Step 5 Enter the half-duplex timer command to specify the time that the interface delays when in controlled
carrier mode. For example, to configure the DCD drop delay, enter the following commands, using
appropriate values for your system:
interface serial 2
half-duplex timer dcd-drop-delay 100 ms
The amount of time is specified in milliseconds.
Enter the timer command to tailor the delay times for the router ports.
and their default settings.
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"Installing the Router" and then power up the router.
Table 4-2: Half-Duplex Timer Commands
"Connecting the Console Terminal and
Table 4-2 lists the timer commands