Why do I observe the GTS PMA link functionality failure when the configured data rate is low (~ <7Gbps) and when the PMA link is placed under internal serial loopback mode?

Description

Due to a problem in the Quartus® Prime Pro Edition Software version 24.1, when the GTS PMA link data rate is < 7 Gbps, and when you change the RX adaptation mode from ‘auto’ (default) to ‘manual’, you might see the transceiver functionality failure when the PMA link is placed under internal serial loopback mode. 

Resolution

There is no workaround for this problem currently. If the situation permits, you can setup the external serial loopback path for testing the PMA/FEC direct mode for use cases with data rates <7 Gbps and with RX manual adaptation mode enabled.