PMC-Sierra PM5349 manual Bit Error Rate Monitor, Synchronization Status Extraction

PMC-Sierra, Inc.

S/UNI-QUAD

DATASHEET

PM5349 S/UNI-QUAD

PMC-971239 ISSUE 6 SATURN USER NETWORK INTERFACE (155-QUAD)

10.4.2Bit Error Rate Monitor

The Bit Error Monitor Block (BERM) calculates the received line BIP-24 error detection code (B2) based on the line overhead and synchronous payload envelope of the receive data stream. The line BIP-24 code is a bit interleaved parity calculation using even parity. Details are provided in the references. The calculated BIP code is compared with the BIP-24 code extracted from the B2 byte(s) of the following frame. Any differences indicate that a line layer bit error has occurred. Up to 192000 (24 BIP/frame x 8000 frames/second) bit errors can be detected per second for STS-3c (STM-1) rate.

The BERM accumulates these line layer bit errors in a 20 bit saturating counter that can be read via the microprocessor interface. During a read, the counter value is latched and the counter is reset to 0 (or 1, if there is an outstanding event). Note, this counter should be polled at least once per second to avoid saturation which in turn may result in missed bit error events.

The BERM block is able to simultaneously monitor for signal fail (SF) or signal degrade (SD) threshold crossing and provide alarms through software interrupts. The bit error rates associated with the SF or SD alarms are programmable over a range of 10-3to 10-9. Details are provided in the Operations section.

In both declaring and clearing detection states, the accumulated BIP count is continuously compared against the threshold. This allows to rapidly declare in the presence of error bursts or error rates that significantly exceed the monitored BER. This behavior allows meeting the ITU-T G.783 detection requirements at various error rates (where the detection time is a function of the actual BER, for a given monitored BER.

10.4.3Synchronization Status Extraction

The Synchronization Status Extraction (SSE) Block extracts the synchronization status (S1) byte from the line overhead. The SSE block can be configured to capture the S1 nibble after three or after eight frames with the same value (filtering turned on) or after any change in the value (filtering turned off). The S1 nibble can be read via the microprocessor interface.

Optionally, the SSE can be configured to perform filtering based on the whole S1 byte. Although this mode of operation is not standard, it might become useful in the future.

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