Description
Due to a problem in the Quartus® Prime Standard Edition Software version 18.1, you may see this internal error when compiling a design that instantiates one or more Clock Control Blocks(ALTCLKCTRL).
This problem occurs when targeting Cyclone® V devices.
Resolution
To work around this error, remove the Clock Control Blocks(ALTCLKCTRL) from the design and fit the design automatically.
This problem is fixed starting with the Quartus® Prime Standard Edition Software version 19.1.