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Cisco 819 Series Integrated Services Routers Software Configuration Guide
OL-23590-02
Chapter 8 Configuring the Serial Interface
How to Configure Serial Interfaces
SUMMARY STEPS
1. ignore-dcd
DETAILED STEPS
Caution Unless you know for certain that you really need this feature, be very careful using this command. It will
hide the real status of the interface. The interface could actually be down and you will not know just by
looking at show displays.
Specifying the Serial Network Interface Module Timing
On Cisco 819 ISRs, you can specify the serial Network Interface Module timing signal configuration.
When the board is operating as a DCE and the DTE provides terminal timing (SCTE or TT), you can
configure the DCE to use SCTE from the DTE. When running the line at high speeds and long distances,
this strategy prevents phase shifting of the data with respect to the clock.
To configure the DCE to use SCTE from the DTE, use the following command in interface configuration
mode.
SUMMARY STEPS
1. dce-terminal-timing enable
DETAILED STEPS
When the board is operating as a DTE, you can invert the TXC clock signal it gets from the DCE that
the DTE uses to transmit data. Invert the clock signal if the DCE cannot receive SCTE from the DTE,
the data is running at high speeds, and the transmission line is long. Again, this prevents phase shifting
of the data with respect to the clock.
To configure the interface so that the router inverts the TXC clock signal, use the following command in
interface configuration mode.
Command or Action Purpose
Step 1
ignore-dcd
Example:
Router(config-if)# ignore-dcd
Configures the serial interface to monitor the DSR
signal as the line up/down indicator.
Command or Action Purpose
Step 1
dce-terminal-timing enable
Example:
Router(config-if)# dce-terminal-timing enable
Configures the DCE to use SCTE from the DTE.