zl30102 Zarlink Semiconductor, zl30102 Datasheet - Page 27

• Manufacturer Part Number: zl30102
• Description: T1/e1 Stratum 4/4e Redundant System Clock Synchronizer For Ds1/e1 And H.110
• Manufacturer: Zarlink Semiconductor

ZL30102
Data Sheet
The method of clock redundancy shown in Figure 18 is that the redundant timing card is frequency and phase
locked to the active clock and frame pulse. The redundant card is configured as Secondary Master (SEC_MSTR=1)
and continuously adjusts the phase of its output clocks and frame pulses to match that of the active clock and frame
pulse. In this mode of operation, the bandwidth of the redundant timing card’s DPLL is much larger than that of the
active timing card’s DPLL, 922 Hz versus 1.8 Hz. Therefore the redundant clocks and frame pulses will track the
active clock and frame pulse closely even in the presence of the maximum tolerable input jitter and wander on the
active timing card’s reference input.
The method of synchronization using REF2 and REF2_SYNC is enabled as soon as a valid 8 kHz frame pulse is
detected on the REF2_SYNC input. The REF2_SYNC pulse must be generated from the clock that is present on
the REF2 input. The ZL30102 checks the number of REF2 cycles in the REF2_SYNC period. If this is not the
nominal number of cycles, the REF2_SYNC pulse is considered invalid. For example, if REF2 is a 8.192 MHz clock
and REF2_SYNC is a 8 kHz frame pulse, then there must be exactly 1024 REF2 cycles in a REF2_SYNC period. If
a valid REF2_SYNC pulse is detected, the ZL30102 will align the rising edges of the REF2 clock and the
corresponding output clock such that the rising edge of the F8o/F32o output frame pulse is aligned with the frame
boundary indicated by the REF2_SYNC signal. The rising edges of the REF2 and the corresponding output clock
that are aligned, are the ones that lag the rising edges of the REF2_SYNC and the F8o pulses respectively. This is
illustrated in Figure 17. Many combinations of the ZL30102 clock and frame pulse outputs can be used as REF2
and REF2_SYNC inputs. In general, the active low frame pulses F4o, F16o and F65o would be inverted first before
used as a REF2_SYNC input.
REF2_SYNC = 8 kHz
REF2 = C8o
aligned
F8o
C8o
Figure 17 - Examples of REF2 & REF2_SYNC to Output Alignment
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Zarlink Semiconductor Inc.