General Description: When the syntax "RISING_EDGE" is used within a VHDL design analyzed by FPGA Express 1.x or 2.0.x, the following error will occur:
Error: Could not find object subprogram RISING_EDGE. This error can occur if a package (World) that exists in memory also exists in another library referred to in a Library statement. This error can also occur if the package uses synthesis_off/synthesis_on directives around the object. (VHDL-2204)
RISING_EDGE is not supported by FPGA Express 1.x or 2.0.x.
should be replaced by
(CLK'event and CLK='1')
RISING_EDGE is supported by FPGA Express 2.1.x and newer.