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:
Use the enable command and password to enter privileged EXEC mode. You are in privileged EXEC mode when the
Step 1
prompt changes to
Gateway> enable
Password: password
Gateway#
Enter global configuration mode. You are in global configuration mode when the prompt changes to
Step 2
Gateway# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Gateway(config)#
Perform one of the following, depending on your configuration:
Step 3
• 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.
DS1 port specifies T1 port.
Note
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}
Return to privileged EXEC mode:
Step 4
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#
.
Gateway#
Gateway(config)#.
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