Error (10779): VHDL error at < filename.vhd >: expression is not constant.

Description

Due to a problem in the Quartus® II software version 13.1 and earlier, you may see this error message if you use a variable as an index for signal.

For example :

data(a downto b) where a and b are variables

Resolution

To workaround this problem, use a 3rd party synthesis tool or avoid this code construct.

This problem is scheduled to be fixed in a future release of the Quartus II software.