zl30407qcc Zarlink Semiconductor, zl30407qcc Datasheet - Page 34

• Manufacturer Part Number: zl30407qcc
• Description: Sonet/sdh Network Element Pll
• Manufacturer: Zarlink Semiconductor

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 of timing cards. 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 ZL30407 should be switched into Normal mode (with MS2, MS1 set to 00) instead of Holdover mode. If the
reference clock is available, the ZL30407 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 ZL30407 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 system is connected to the network (or timing card switched to a valid reference) the Acquisition PLL will
quickly synchronize and clear its own Holdover status (PAH bit). This will enable the Core PLL to start the
synchronization process. After acquiring lock, the ZL30407 will automatically switch from Holdover into Normal
mode without system intervention. This transition to the Normal mode will be flagged by the LOCK status bit and
pin.
RESET = 1
System Start-up Sequence: FREE-RUN --> HOLDOVER --> NORMAL
RESET
unconditional return from
MS2,MS1 = 10 forces
any state to Free-run
FREE-
RUN
10
MS2,MS1 = 00
MS2,MS1 = 01
Figure 9 - Transition From Free-run to Normal Mode
OR
MS2,MS1 = 01 OR
RefSel change
HOLD-
OVER
01
Zarlink Semiconductor Inc.
MS2,MS1 = 00
Ref: OK AND
ZL30407
{AUTO}
34
RefSel Change
MS2,MS1 = 01
NORMAL
00
OR
Ref: OK-->FAIL AND
MS2,MS1 = 00
{AUTO}
HOLD-
AUTO
OVER
Ref: FAIL-->OK AND
MS2,MS1 = 00 AND
AHRD = 0
{AUTO}
Ref: FAIL-->OK AND
MS2,MS1 = 00 AND
AHRD = 1 AND MHR = 1
{MANUAL}
AHRD = 1 AND
MHR = 0
OR
Data Sheet