Alcatel MainStreet 2902, Manual, Page: 205 / 344

19 — X.21 and V.35 DCMs
2902 MainStreet Technical Practices 19-11
May 2002 90-2906-01
Type of synchronous clocking
For both the X.21 and V.35 DCMs, when you configure the type of synchronous
clocking, you are configuring the effect that the 2902 MainStreet system has on
clocks passing through it. The type can be set:
•
to the timing of the 2902 MainStreet system (LOCKED) (default)
•
to be passed through transparently (INDEPNT)
If the clocking for a circuit is independent, the clocking information is embedded in
the signaling bit of an HCM frame and passed through transparently. Deviations of
up to 50 b/s relative to the nominal rate can be accommodated.
For more information, ask your supplier representative for Configuration Note
NCN305, entitled “Data Interface Clocking”.
Receive clock
The receive clock on X.21 DCMs with revision 2 DRAGA can be inverted. The
default is no inversion. Receive clock inversion can compensate for a phase shift
between the transmit clock and receive data signals, if it occurs.
If you are experiencing high bit error rates (sometimes due to a combination of
interface speed, cable length and DCM clocking configurations) try inverting the
receive clock (RX_INV).
Procedure 19-8 To configure clocking
The RX_INV/NO_RX_INV softkey applies to the X.21 circuits only.
where pp is 1 or 9, and c is 1
* Default
Note —
The INTERNAL softkey is not available if transparent rate
adaption is selected.
RX_INV
/NO_RX_INV*
INTERNAL EXTERNAL LOCKED*
/INDEPNT
SLAVE*
CONFIG — CIRCUIT — < pp-c >
↵
— FUNCTION — CLOCKING
SK000506