Nortel DCT1900 Technical Product Manual page 174

Technical Product Manual - DCT1900
Installation Instructions, Central Processing Unit (CPU) – REX-BRD0004 or 2/ROFNB 157 19/2
Strap Settings
As the master CPU determines the timing in the star network, it can either generate the frame
timing on its own or synchronize it to an external source like a 2 Mbit/s link (DLU or DTU).
Synchronizing to a 2 Mbit/s or 1.544Mbit/s link reduces the likelihood of frame slips on the link but
is only allowed when the clock stability is better than 2 ppm. In the Master/Stand Alone mode the
CPU provides the frame timing on its own. As a Slave/Standalone the CPU receives framing sync
from the master RE. In Figure 5–2 an overview of the strap settings is given.
When setting the CPU up as a master or slave, both of the Air Interface master/slave jumpers
must be set the same. Refer to Figure 5.2 for the correct configuration.
When the CPU is strapped as a master, the frame timing strap must be set correctly. Refer to
Figure 5.2 for the correct configuration.
When the CPU is strapped as a slave, the function of the frame timing strap is disabled and the
position of this strap is irrelevant. If the CPU is strapped as a slave then there must be a Sync
cable from the Sync Out on the master RE connected to the Sync In connector on the slave.
Refer to Chapters 17 and 19 in Section 5 of the TPM for information on Sync cable connectivity.
5-2
Slave
Master Slave
Slave
Level 1
Level 2
Fig. 5–1 Synchronization Topology
Slave
Slave
Slave
Install-DCT1900/R8/mw
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