zl30410 Zarlink Semiconductor, zl30410 Datasheet - Page 18

• Manufacturer Part Number: zl30410
• Description: Multi-service Line Card Pll
• Manufacturer: Zarlink Semiconductor

5.0
This section provides application examples frequently found in a typical Line Card being part of Network Element
operating in a synchronous network.
5.1
The ZL30410 is designed to transition from one mode to the other driven by the internal State Machine or by
external control. The following examples present a couple of typical scenarios of how the ZL30410 can be
employed in network interface line cards.
5.1.1
The FREE-RUN to HOLDOVER to NORMAL transition represents a sequence of steps that will most likely occur
during a new system installation or scheduled maintenance. The process starts from the RESET state and then
transitions to Free-run mode where the system (card) is being initialized. At the end of this process the ZL30410
should be switched into Normal mode (with MS2, MS1 set to 00) instead of Holdover mode. If the reference clock is
available, the ZL30410 will transition briefly into Holdover to acquire synchronization and switch automatically to
Normal mode. If the reference clock is not available at this time, as it may happen during new system installation,
then the ZL30410 will stay in Holdover indefinitely. While in Holdover mode, the Core PLL will continue generating
clocks with the same accuracy as in the Free-run mode, waiting for a good reference clock. When the line card
become connected to the timing card the Acquisition PLL will quickly synchronize and clear its own Holdover status.
This will enable the Core PLL to start the synchronization process. After acquiring lock, the ZL30410 will
automatically switch from Holdover into Normal mode without system intervention. This transition to the Normal
mode will be flagged by the LOCK status pin.
ZL30410 Switching Between Clock Modes
Applications
System Start-up Sequence: FREE-RUN --> HOLDOVER --> NORMAL
C20i Clock
Figure 7 - Primary and Secondary Reference Out of Range Thresholds
+4.6 ppm
-4.6 ppm
0 ppm
Accuracy
-20
-16.6 -13.8
-15
-12
-10
-9.2
-7.4
Zarlink Semiconductor Inc.
-5
-4.6
-4.6
C20
ZL30410
C20
0
18
0
0
0
C20
4.6
4.6
5
7.4
9.2
10
12
13.8 16.6
15
20
Out of Range
In Range
Out of Range
In Range
Out of Range
In Range
Frequency
Offset [ppm]
Data Sheet