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Cisco Broadband Cable Command Reference Guide
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Chapter 2 Cisco CMTS Configuration Commands
cable clock source-midplane
cable clock source-midplane
To make the midplane time-division multiplexing (TDM) clock the primary timing reference for the
clock card, use the
cable clock source-midplane
command in global configuration mode. To disable the
selection and return to the default, use the
no
form of this command.
cable clock source-midplane
no cable clock source-midplane
Syntax Description
This command has no keywords or arguments.
Defaults
The clock card does not get its timing reference from the midplane TDM clock.
Command Modes
Global configuration
Command History
Usage Guidelines
Because the clock card automatically provides the timing reference to the midplane TDM clock, the
midplane cannot in turn act as the reference for the clock card. This means that the
cable clock source-
midplane
command does not take effect unless a port adapter is configured as the primary clock
reference source for the midplane.
Note
This command is not applicable on the SC train.
To support the clock feature set in VoIP configurations, a Cisco uBR7246 VXR chassis, equipped with
a clock card; and a Cisco uBR-MC16S, a Cisco uBR-MC16E, or a Cisco uBR-MC28C cable interface
line card must be used running Cisco IOS Release 12.1(1a)T1 or higher releases. Only these cable
interface line cards support the external clock card reference from a clock card to distribute that signal
to CMs or set-top boxes (STBs) attached to the specific network segments. You can use other cable
interface cards, such as the Cisco uBR-MC16C, with the clock card, but these other cable interfaces will
not synchronize their downstream SYNC messages with the external clock source.
Each CM or STB must also support VoIP applications and the clock feature set. The Cisco uBR924,
running Cisco IOS Release 12.0(7)T or later releases, supports the clock card feature automatically.
Examples
The following example shows how to set the primary clock reference to the midplane TDM clock:
Router(config)#
cable clock source-midplane
Router(config)#
Release
Modification
12.1(1a)T1
This command was introduced.
12.1(2)EC1
This command was supported on the EC train.
