External Clock, Free-Running Clock | Cisco Systems AS5400XM specification

External Clock

The TDM bus can be synchronized with an external clock source that can be used as an additional network reference. If no clocks are configured, the system uses a primary clock through a software-controlled default algorithm. If you want the external T1/E1 clock (through the BITS interface) as the primary clock source, you must configure it using the dial-tdm-clock priority CLI command; the external clock is never selected by default.

The BITS interface requires a T1 line composite clock reference set at 1.544 MHz and an E1 line composite clock reference set at 2.048 MHz.

Free-Running Clock

If there is no good clocking source from a feature card card or an external clock source, then specify the free-running clock from the local oscillator using the dial-tdm-clock priority CLI command.

To configure the clock source and clock source priority used by the TDM bus, follow these steps:

Step 1 Use the enable command and password to enter privileged EXEC mode. You are in privileged EXEC mode when the prompt changes to Gateway#.

Gateway> enable

Password: password

Gateway#

Step 2 Enter global configuration mode. You are in global configuration mode when the prompt changes to Gateway(config)#.

Gateway# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Gateway(config)#

Step 3 Perform one of the following, depending on your configuration:

•Configure the CT1/CE feature card clock priority, trunk slot, and port that are providing the clocking source. Priority range is defined as a value from 1 to 99. Trunk slot is defined as a value from 1 to 7. DS1 port is defined as a value from 0 to 7.

Note DS1 port specifies T1 port.

Gateway(config)# dial-tdm-clock priority priority# {external freerun slot/ds1 port}

•Configure the CT3 feature card clock priority, trunk slot, and port that are providing the clocking source. Priority range is defined as a value from 1 to 99. Feature card slot is defined as a value from 1 to 7. DS3 port specifies the T3 port. DS1 port number controller is defined as a value between 1 and 28.

Gateway(config)# dial-tdm-clock priority priority# {external freerun slot/ds3 port:ds1 port}

Step 4 Return to privileged EXEC mode:

Gateway(config)# Ctrl-Z

Gateway#

Tip To save the gateway configuration, save it to NVRAM. See the “Saving Configuration Changes” section on page 60.

Clocking Configuration Examples

In the following example, a BITS clock is set at priority 1:

Gateway(config)# dial-tdm-clock priority 1 external

Gateway(config)# exit

Gateway#