Why is the manual lock to reference mode of the GTS transceivers in Agilex® 5 FPGA not working as expected?

Description

Due to a problem in the Quartus® Prime Pro Edition software version 25.1.1 and earlier, the manual lock to reference mode of the GTS transceivers in Agilex® 5 FPGA does not work as expected.

Resolution

For a workaround, users will need to follow the following steps to enable the manual lock to reference mode to function properly. 

• Write 0x1 to 0x818 [0] for Software Reset Controller(SRC) to ignore the CDR LTD status. 
• Write 0x1 to both 0x91680 [24] and 0x91680 [28] for enabling LTR mode 
• Write 0x1 to both 0x91580 [30] and 0x91580 [31] for enabling RX parallel data in manual LTR mode  

The manual LTR mode will only work when adaptation is set to manual. 

This problem is fixed beginning with the Quartus Prime Pro Edition software version 25.3.