zl50118gag2 Zarlink Semiconductor, zl50118gag2 Datasheet - Page 58

• Manufacturer Part Number: zl50118gag2
• Description: 32 Channel 1 T1/e1 Cesop Processor With Single Ethernet Interface
• Manufacturer: Zarlink Semiconductor

7.2
For applications where there is no common reference clock between provider edge units, an adaptive clock
recovery technique is provided. The Adaptive clock recovery solution provided in the Zarlink CESoP products is a
combination hardware and software. The chip contains a DCO per TDM port in unstructured mode, that enables the
recovery of up to 32 independent clocks. The timing algorithm resides in the API and runs out of the host processor.
The basic information is transmitted using timestamps. Current CES standards allow for using of timestamps.
Timestamps may be implied by the value of the sequence numbers, or it can be formatted as RTP timestamps.
When a packet containing TDM data is sent, an RTP timestamp and/or sequence number is placed into the packet
header. On arrival at the receiving device, the arrival time is noted in the form of a local timestamp, driven by the
output clock of the TDM port it is destined for.
The recovered clock at the egress point of the ZL5011x is based on non-linear filtering of the timestamps that are
carried in the CESoP packets. The performance of the clock recovery is greatly improved by applying these
non-liner filtering techniques. The adaptive clock recovery performance is dependent on the network configuration
and operation, if the loading of the network is constrained, then the wander of the recovered clock will not exceed
the specified limits.
Adaptive Clock Recovery
LIU
Data
Source
Clock
Source
Clock
ZL5011x
source
node
ZL5011x
source
node
Timestamp
generation
Figure 20 - Differential Clock Recovery
Figure 21 - Adaptive Clock Recovery
ZL50115/16/17/18/19/20
Packets
Packets
Zarlink Semiconductor Inc.
Network
Network
clock
PRS
58
Packets
Packets
ZL5011x
destination
node
Host CPU
ZL5011x
destination
node
Timestamp
Queue
Stamp
Host CPU
Time
extraction
recovery
Timing
monitor
Queue
DCO
DCO
Data
Dest'n
Clock
Dest'n
Clock
LIU
Data Sheet