Achronix Speedster22i SerDes - Manual (Page 41)

The transmit pattern generator can optionally transmit user defined patterns instead of PRBS
patterns, configured through the control registers. Two sets of user defined patterns (up to
40-bits each) can be configured. The user can decide to send a single 40-bit pattern or two
alternate 40-bit patterns.
The transmit test pattern generation supports two modes of operation -
• Non-framed transmit mode
• Framed transmit mode
In both modes, the shift registers used for PRBS generation should be initialized to a non-zero
value.
In the non-framed transmit mode, the user has the option of selecting one of the supported
PRBS patterns or the user defined pattern. When reset is released, the pattern generator
continuously transmits the selected pattern.
In the framed transmit mode, the user can select to transmit one or both user defined patterns
initially, followed by one of the PRBS patterns. The switch over from user defined pattern to
PRBS pattern is controlled by programming register. The PRBS patterns can also be
interspersed with the user defined patterns.
PCS Test Pattern Checker
The test pattern checker on the receive data-path supports checking all PRBS patterns that
can be generated from the transmit side. The receive pattern checked also has two operating
modes:
• Non-framed mode
• Framed mode
In the non-framed mode of operation, the test pattern checker implements self-synchronizing
PRBS checkers. If a user defined pattern (UDP) is being transmitted in non-framed mode, the
symbol alignment block needs to be setup to achieve byte lock (to the first byte of the
repetitive UDP). The test pattern checker should start checking for errors after symbol
alignment block has indicated that byte lock has been achieved.
If a PRBS pattern is being transmitted, then the test pattern checker is self-synchronized to
the incoming data. Once the checker locks to the incoming data, it can track any errors with
respect to incoming data.
In the framed mode of operation, the receive pattern checker will use the same seed as the
transmit pattern generator for checking the PRBS patterns. The symbol alignment block
needs to be setup to lock for the initial UDP. The test pattern checker monitors the locked
data and detects the switch over from the initial pattern to the PRBS pattern and triggers the
receive side PRBS checking.
In non-framed PRBS mode, the test pattern checker increments an error counter for every
received data that did not match the expected pattern after a window of wait period has
expired.
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