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HBhat2's avatar
HBhat2
Icon for Contributor rankContributor
6 years ago

Electrical IDLE in Transceiver

Hi, My requirement is keep the transceiver lines in Electrical Idle whenever the Logical Layer FSM goes into low power state. I found that we can select "Enable tx_PMA_elecidle port" under TX PMA ...
CheepinC_altera's avatar
CheepinC_altera
Icon for Regular Contributor rankRegular Contributor
6 years ago

Hi HPB,

Yes, your understanding of the lock-to-ref is correct. When there is no valid data at the RX, the CDR will in LTR mode. Note that in actual hardware, you may see this rx_is_lockedtoref and rx_is_lockedtodata toggle periodically because the CDR will attempt to lock-to-data from time to time.

Regarding the frequency of the rx_clkout, the output frequency will stay at 312.5MHz even though it is in LTR mode. It is following 20G/64. When CDR achieves lock-to-data, it is tracking the ppm difference between the incoming data and the RX local refclk. The nominal frequency will still be 312.5MHz with some ppm difference only.

Please let me know if there is any concern. Thank you.

Best regards,

Chee Pin