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FibreXtreme User Guide
OPERATION
Copyright 2017
6.4.2 Loop Enable
The loop-enable option allows the SL240 PCIe card to transmit the received Serial FPDP data
stream again. When loop enable is on, it implies that this node is designated as a receiver in the
current configuration.
6.4.3 Receiver/Transmitter Enable
The transmitter-enable and receiver-enable settings can turn off the transmit and receive Serial
FPDP data streams, respectively. Neither affects the loop operation, so data will still be
retransmitted if the loop operation is enabled. This makes these options useful for record/
playback systems where you wish to retransmit merely the data received without processing it.
The receive-enable is useful for disabling the receive FIFO for the master in loop operation so
that the data sent is not received.
6.4.4 CRC Generation/Checking
The CRC Generation/Checking option allows the SL240 card to detect data transmission errors.
The card is not capable of correcting the errors. Error correction is left to application level
design.
A single bit controls both generation and checking. CRC should be used in almost all applications.
It offers excellent coverage of data errors and has very little impact on link throughput for
maximum frame sizes. The option of disabling CRC is only retained for compatibility with older
third-party devices. Both nodes on the link (or all nodes in a loop configuration) should be set to a
common CRC mode or the resulting mismatch will cause data errors and/or link errors.
6.4.5 Stop on Link Error of/SYNC
There are two DMA stop conditions available to the user—stop on link error and stop on /SYNC.
The stop on link error stops the DMA engine from removing data from the receive FIFO when
there is a link error, such as the link going down. The stop on /SYNC option allows you to stop
data from being received from the receive FIFO when a /SYNC without /DVALID is received on
the output.
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