Using Exemplar Leonardo 4.22 for synthesis, and MTI MdoelSim EE or QuickHDL for simulation when I go to do a timing simulation with the time_sim.vhd from the Xilinx tools and run vcom (MTI), or qvhcom (QuickHDL) I get an error similiar to the following:
ERROR:time_sim.vhd(132): Cannot assign to object with mode IN:ce
In my code I have declared the port ce as an in std_logic. My syntheszied design goes through the Xilinx M1 tools without any error or warnings all the way to the bitstream.
A possible cause of this error is if the user defines a signal or port in the design called ce, and also has at least one flop with a clock enable signal.
This is a bug in Leonardo 4.22 in that when synthesizing the VHDL code if the user defines a signal or port in the design called lower case ce, and also has any flops with a clock enable in the design, will call the signal to the flops clock enable 'CE'. This error will occur when compiling the time_sim.vhd netlist. Leonardo by default will name the signal going to the flop clock enables uppercase CE, which is fine if the user name is lower case ce, and will go through the Xilinx tools just fine. The problem occurs in Modelsim which is case insensative.
This will not cause any implmentation problem with Xilinx, and will only give errors with case insensative tools. This naming problem will be fixed in the next release of Exemplar's software, Leonardo Spectrum.
The only workaround for now is to not use the name 'ce' for a signal or port in the input VHDL.