S/UNI®-8x155 ASSP Telecom Standard Product Data Sheet
Released
Figure 7 CRC Decoder
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10.7.6 Performance Monitor
The Performance Monitor consists of four 16-bit saturating error event counters and one 24-bit
saturating received good packet counter. One of the error event counters accumulates FCS
errors. The second error event counter accumulates minimum length violation packets. The
third error event counter accumulates maximum length violation packets. The fourth error
event counter accumulates aborted packets. The 24-bit receive good packet counter counts all
error free packets.
Each counter may be read through the microprocessor interface. Circuitry is provided to latch
these counters so that their values can be read while simultaneously resetting the internal
counters to 0 or 1, whichever is appropriate, so that a new period of accumulation can begin
without loss of any events. The counters should be polled at least once per second so error
events will not be missed.
The RXFP monitors the packets for both minimum and maximum length errors. When a packet
size is smaller than MINPL[7:0], the packet is marked with an error but still written into the
FIFO. Malformed packets, that is packets that do not at least contain the FCS field plus one
byte, are treated differently. If a malformed packet is received and FCS stripping is enabled, the
packet is discarded, not written in the FIFO, and counted as a minimum packet size violation. If
a malformed packet is received and FCS stripping is disabled, it is written into the FIFO since,
in this case, the misformed packet criteria is reduced to one byte, but will still count as a
minimum packet size violation. When the packet size exceeds MAXPL[15:0] the packet is
marked with an error and the bytes beyond the maximum count are discarded.
10.8 Transmit Line Interface (CSPI)
The Transmit Line Interface allows to directly interface the S/UNI-8x155 with optical modules
(ODLs) or other medium interfaces. This block performs clock synthesis and performs parallel
to serial conversion on each outgoing 155.52 Mbit/s data stream.
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC- 2010299, Issue 2
79
PMC [ PMC-SIERRA, INC ]
