5.6.5.3. PBXXX Partial Integration (DIU-S2-Emulation) 
This is a configuration of PBXXX, where the PBXXX takes power from
the backplane. In addition the PBXXX can receive a reference clock from
the OpenScape 4000 backplane, or supply a reference clock to the OpenScape
4000 backplane.
In this case the PBXXX emulates the DIU-S2 functionality: It looks
like a DIU-S2 to the OpenScape 4000 and communicates with the OpenScape
4000 backplane's D-channel signalling highway using layer 3 CorNet-N/NQ
messages. In addition maintenance messages are passed between the PBXXX
and the OpenScape 4000 backplane.
The CDGM tool is required for PBXXX configuration and debugging.The
CDGM PC also provides the loadware for the PBXXX. The PBXXX board will
receive all the configuration data and maintenance commands via the V24
port.
Features:
- PBXXX will always synchronize on the PCM clock from the OpenScape 4000 backplane. Additionally, the PBXXX will be able to provide OpenScape 4000 with the clocksources derived from the incoming data stream from the DPNSS1 or DASS links. These clocksources can be switched on and off under OpenScape 4000 control by means of DIU-S2 backplane messages.
- Between B channels on the Network side (DPNSS/DASS) a fixed relationship exists (see B channel negotiation). Timeslot connections are made on a per call basis, however no physical connection will be established until OpenScape 4000 assigns a timeslots on the backplane for the selected B-channel.