GX3290 Datasheet, PDF (26/47 Pages) Semtech Corporation – 290 x 290 3.5Gb/s Crosspoint Switch

4.6.2 Pattern Checker
The pattern checkers de-serialize incoming serial data before checking for errors in the
parallel domain. Three comparison modes are supported:
1. Neutral Phase Comparison Mode. The incoming data is re-timed in a CDR, and
sampled at the neutral (eye center) phase recovered by the CDR before
de-serialization. Errors with respect to the supported PRBS sequences can be
counted.
2. Offset Phase Comparison Mode. The phase at which the incoming data is
sampled with respect to the recovered clock is adjustable over a full UI. Errors with
respect to the supported PRBS sequences can be counted. By sweeping the
sampling phase and counting errors at each phase, an error rate “bathtub curve”
can be recorded, and the horizontal eye opening evaluated.
3. Arbitrary Data Comparison Mode. This mode can operate on arbitrary data
patterns. The incoming serial data is sampled at both the neutral phase and the
adjustable phase, and each of the two sampled data streams is de-serialized and the
two streams are compared in the parallel domain.
The pattern checker allows a true measurement of bit error rate for the supported PRBS
sequences in the first two modes above. The third, arbitrary data comparison mode,
gives an indication of the degree of eye closure at a given sampling phase offset, but
cannot detect bit errors in the incident data. See Figure 4-1 and Figure 4-2 below.
EXT_PG0/EXT_PG0
Input 288
Crosspoint Core
(290 x 290)
Output 288
MON0/MON0
/2 /11
Serializer/
Pattern
Generator
Pattern
/2 CMU _{Generator 0}
xtal osc.
27MHz
CDR
/2
Pattern
Checker 0
Neutral
Phase
Deserializer
Variable
Phase
Deserializer
Pattern Checker
Figure 4-1: Simplified Pattern Generator/Checker Zero Block Diagram
GX3290 290 x 290 3.5Gb/s Crosspoint
Final Data Sheet Rev. 2
GENDOC-053317 March 2013
www.semtech.com
26 of 47
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