Description
Automatic PLL merging will only take place during compilation when the configuration of both pll's are identicle.
The SPI4.2 RX PLL may be configured as "Real time configurable". However, as the TX PLL will not have the "Real time configurable" option enabled, then automatic PLL merging may not take place.
If SPI4.2 RX and TX PLL merging is required for your design, you can enforce by this using the following assignment:
set_instance_assignment -name FORCE_MERGE_PLL ON -from "<tx_pll>" -to "<rx_pll>"