Configuring The Clock Source; Inverting Et-Clock; Inverting Txclock Or Rxclock - HP ProCurve 7000dl Series Basic Management And Configuration Manual

Configuring the Clock Source

The serial interface must have a clock source to synchronize the transmission
of data. The clock source for the serial interface is called the external transmit
reference clock (et-clock). By default, the source for et-clock is set to
txclock, which means that the serial interface takes the clock from the
transmit signal.
If you need to configure the clock source for the serial line, enter the following
command from the serial interface configuration mode context:
Syntax: et-clock-source <source>
There are two possible sources:
txclock, the default setting
rxclock, which specifies that the serial interface should take the clock
from the receive signal
Your public carrier should tell you which setting to use.

Inverting et-clock

If the cable that connects the serial module to the CSU/DSU is long, it may
cause a phase shift in the data transmitted. If this happens, you must invert
et-clock by entering:
ProCurve(config-ser 1/1)# invert etclock
After you enter this command, the serial module inverts et-clock in the data
stream before transmitting it.
To return et-clock to its default setting, enter:
ProCurve(config-ser 1/1)# no invert etclock

Inverting txclock or rxclock

If the cable that connects the serial module to the CSU/DSU is long, the CSU/
DSU may be configured to invert the transmit clock. You must then configure
the serial interface so that it can receive the inverted clock. Enter one of the
following commands:
Syntax: invert txclock
Syntax: invert rxclock
Configuring Serial Interfaces for E1- and T1-Carrier Lines
Serial Interface: Configuring the Physical Layer
5-13