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For extraxting data from a 576Mbps serial datastream (subLVDS) with a DDR clock of 288MHz I would like to use the transceiver inputs of the Cyclone V.
Can I do this easily? Can I use the transceiver input as a diff. IO?
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You can, but it will take a little extra work.
Although the transceivers accept LVDS signals, they do not operate like an LVDS SERDES. The transceiver receivers contain clock-and-data recovery (CDR) units with a PLL that normally initially locks to a reference clock, and then transitions to locking to data transitions (so that the transceiver clock captures the data in the center of the eye-pattern). Since your LVDS signal has both data and clock, its likely that the data stream does not have enough transitions to guarantee the operation of the CDR. You would need to configure the transceiver CDR in lock-to-reference mode, and then use the DDR clock as the reference to the CDR PLL. Since the CDR would remain in lock-to-reference mode, the data capture is unlikely to be ideal (the received high-speed clock would not be in the center of the data eye). You can deal with this in a couple of ways; program the PLL phase-shift (via the scan-chain), or over-sample the LVDS signal, and add logic to look for the "correct" samples. Since your data stream is at the low-end of the supported data rates, you'll likely need to oversample anyway.
Cheers,
Dave
Honored Contributor
