User Manual

DXU Distribution Switch Unit
4 Function Description
This section decribes the DXU functions. The DXU consists of the following
main blocks:
• PCM part
• Central Positioning Unit (CPU)
• Central Timing Unit (CTU)
• High Level Data Link Controller (HDLC) concentrator
• TG Synchronization (only DXU-11)
The figure below shows a block diagram of the DXU.
P005790A
CPU Part
PCM Part
Inter-
faces
W_dog
CPU
SRAM
Indi-
cators
BOOT/
FLASH
DRAM
Central
Timing
Unit
HDLC Concentrator
Switch
G 703
G 703
Switch
RS 485
RS 485
POWER
DC/DC
External alarms
OMT Interface
Transport
Network
Interface
Transport
Network
Interface
Timing
Local
Bus A
Local
Bus B
100 Ohm
120 Ohm
A
B
75 Ohm
Oscil-
lator
TG-
Sync
Master timing
Downloop timing
Uploop timing
Figure 1 Block Diagram
PCM Part
The PCM part extracts time slots (TS) from the A-bis
link and pass them to the TRUs over the local bus.
It is possible to connect two PCM lines (ports A and
B) to the DXU for increased capacity or transmission
link redundancy.
The PCM-part includes the Managed Objects Interface
Switch (IS) and Digital Path (DP). The IS reallocates
TSs not used to another RBS, so-called multidrop
(cascading) for enhanced flexibility. The multidrop
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EN/LZT 720 0243 Uen R1A