3Com Router 3031, Command Reference Manual

Page: 160 / 838

160 C
HAPTER
3: I
NTERFACE
M
ANAGEMENT
C
OMMANDS
clock Syntax
clock { dceclk | dteclk1 | dteclk2 | dteclk3 | dteclk4 }
View
Serial interface view
Parameter
dceclk: Sets the interface clock selection mode to DCE clock.
dteclk1: Sets the interface clock selection mode to DTE clock option 1.
dteclk2: Sets the interface clock selection mode to DTE clock option 2.
dteclk3: Sets the interface clock selection mode to DTE clock option 3.
dteclk4: Sets the interface clock selection mode to DTE clock option 4.
Description
Using the clock command, you can set the clock selection mode for a synchronous
serial interface.
By default, dceclk (providing clock to the DTE device) and dteclk3 are selected for
the synchronous serial interfaces at the DCE side and the DTE side.
Different operating clocks are selected for the synchronous serial interfaces
working as DTE and DCE, as shown in the following figure.
Figure 1 Selecting a clock for a synchronous serial interface
In the figure, “TxClk” represents transmitting clock and “RxClk” receiving clock.
As a DCE device is required to provide clock for the remote DTE device, you must
select DCEclk as the operating clock for the synchronous serial interface working
as DCE.
Working as DTE, the synchronous serial interface must accept the clock provided
by the remote DCE. As transmitting and receiving clocks of synchronization
devices are independent, the receiving clock of a DTE device can be either the
transmitting or receiving clock of the DCE device. So is the transmitting clock.
Therefore, four clock options are available for a DTE device.
The following table gives the four clock selection options.
DCE DTE
TxClk
RxClk