ZL50018 ZARLINK [Zarlink Semiconductor Inc], ZL50018 Datasheet - Page 40

• Manufacturer Part Number: ZL50018
• Description: 2 K Digital Switch with Enhanced Stratum 3 DPLL
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

12.1.3.2
If a particular reference needs to have higher priority than the others, the device can be programmed in Automatic
mode with a preferred reference (RCCR Register, PMS2-0 bits = 001). When a preferred reference is selected, the
device can only switch automatically between two references, as shown in Table 8. The preferred reference will be
used as the primary reference and, by default, only its next consecutive reference will be used as the secondary
reference. No more than two references can be used in Automatic mode when a preferred reference is selected.
Figure 22 shows the state diagram for the four valid options of automatic reference switching with a preferred
reference.
Ref 0
Option 1
Option 2
Option 3
Option 4
Figure 21 - Automatic Reference Switching State Diagram with No Preferred Reference
Automatic Reference Switching With Preference
Ref 0 failed
Ref 0 valid
Holdover 0
Holdover 3
Free run
Table 8 - Preferred Reference Selection Options
Primary Reference (Preferred)
Ref 3
Start
All Ref failed
All Ref failed
Ref 0
Ref 1
Ref 2
Ref 3
Ref 2 and 3 failed
and (Ref 0 or Ref 1 valid)
Zarlink Semiconductor Inc.
and (Ref 2 or Ref 3 valid)
ZL50018
Ref 0 and 1 failed
40
All Ref failed
All Ref failed
Holdover 1
Holdover 2
Ref 1
Secondary Reference
Ref 2 failed
Ref 2 valid
Ref 1
Ref 2
Ref 3
Ref 0
Data Sheet
Ref 2