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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
DETAILED STEPS
Setting Transmit Delay
It is possible to send back-to-back data packets over serial interfaces faster than some hosts can receive
them. You can specify a minimum dead time after transmitting a packet to remove this condition. This
setting is available for serial interfaces on the MCI and SCI interface cards and for the HSSI or MIP. Use
one of the following commands, as appropriate for your system, in interface configuration mode.
Configuring DTR Signal Pulsing
You can configure pulsing Data Terminal Ready (DTR) signals on all serial interfaces. When the serial
line protocol goes down (for example, because of loss of synchronization), the interface hardware is reset
and the DTR signal is held inactive for at least the specified interval. This function is useful for handling
encrypting or other similar devices that use the toggling of the DTR signal to reset synchronization. To
configure DTR signal pulsing, use the following command in interface configuration mode.
Ignoring DCD and Monitoring DSR as Line Up/Down Indicator
By default, when the serial interface is operating in DTE mode, it monitors the Data Carrier Detect
(DCD) signal as the line up/down indicator. By default, the attached DCE device sends the DCD signal.
When the DTE interface detects the DCD signal, it changes the state of the interface to up.
In some configurations, such as an SDLC multidrop environment, the DCE device sends the Data Set
Ready (DSR) signal instead of the DCD signal, which prevents the interface from coming up. To tell the
interface to monitor the DSR signal instead of the DCD signal as the line up/down indicator, use the
following command in interface configuration mode.
Command or Action Purpose
Step 1
invert txclock
Example:
Router(config-if)# invert txclock
Inverts the clock signal on an interface.
Step 2
invert rxclock
Example:
Router(config-if)# invert rxclock
Inverts the phase of the RX clock on the UIO serial
interface, which does not use the T1/E1 interface.
Command Purpose
Router(config-if)# transmitter-delay
microseconds
Sets the transmit delay on the MCI and SCI synchronous serial interfaces.
Router(config-if)# transmitter-delay
hdlc-flags
Sets the transmit delay on the HSSI or MIP.
Command Purpose
Router(config-if)# pulse-time seconds
Configures DTR signal pulsing.