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FAQ-How does the SPI block extract timing signal

Publication Date:  2012-07-24 Views:  75 Downloads:  0
Issue Description
The SPI (Synchronous Physical Interface) block has a function of extracting timing signal from STM-N signal. One may ask the question where the timing signal is in the STM-N signal.        
Alarm Information
Handling Process
The timing signal is not part of overhead or payload in the SDH frame. It is extracted from SDH signal waveform. In order to enhance the accuracy of extracting timing signal, the SDH signal is scrambled. The purpose of scrambling is to reduce the possibility of having long sequences of "1" and "0" because it is impossible to extract timing signal from such long sequences of "1" and "0" (no transition event)      


Root Cause


This case is useful for us to understand the abstract about extraction of timing signal.