Altera Corporation
2–213
October 2007
Stratix II GX Device Handbook, Volume 2
Stratix II GX Transceiver Architecture Overview
PRBS10
Pseudo-Random Bit Sequences (PRBS) are commonly used in systems to
verify the integrity and robustness of the data transmission paths. When
the SERDES factor is 10, use the PRBS10 pattern. The PRBS generator
yields 2^10-1 unique patterns. You can use PRBS with or without serial
loopback. In PRBS/ serial loopback mode, the rx_seriallpbken signal is
available. In the PRBS/no loopback mode, this control signal is not
available.
You enable PRBS mode in the Quartus II ALT2GXB MegaWizard Plug-In
Manager. PRBS10 does not use the 8B/10B encoder and decoder. The
8B/10B encoder and decoder are bypassed automatically in the PRBS
mode.
The advantage of using a PRBS data stream is that the randomness yields
an environment that stresses the transmission medium. In the data
stream, you can observe both random jitter and deterministic jitter using
a time interval analyzer, bit error rate tester, or oscilloscope.
The PRBS verifier can provide a quick check through the non-8B/10B
path of the transceiver block. The PRBS verifier is active once the receiver
channel is synchronized. Set the alignment pattern to 10’h3FF for the
10-bit SERDES modes.
The verifier stops checking the patterns after receiving all the PRBS
patterns (1023 patterns for 10-bit mode). The
rx_bistdone
signal goes
high, indicating that the verifier has completed. If the verifier detects an
error before it is finished,
rx_bisterr
pulses high for the time the data
is incorrect. Use the
rx_digitalreset
signal to re-start the PRBS
verification.
The 8B/10B encoder is enabled, so the data stream is DC balanced.
8B/10B encoding guarantees a run length of less than 5 UI, which yields
a less stressful pattern versus the PRBS data. However, since the PRBS
generator bypasses the 8B/10B paths, the incremental BIST can test this
path.
BIST in Double-Width Mode
Double-width mode supports only PRBS7 pattern generation and
verification.
1
The PRBS7 pattern is only available when the SERDES factor is
20 bits.
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