I'm using DSP tools 9.1 with ISE 9.2 and Matlab 2007. I'm using th Black Box block tp import a verilog function to the system. When using a ModelSim Verilog installation, i get a simulation error "cann't find unisim library and vcom".And when using a ModelSim VHDL installation, i get an ellaboration error "A design must be loaded before the find command can be used" and a warning at compilation "Warning:  mult_test_cosim.vhd(1809): A use of this default binding for this component instantiation will result in an elaboration error."
Can any one help me.
I have another question, how can i get an older version of System Generator. I need System Generator 6.1 it was working great.
It sounds like a configuration problem with ModelSim. I would check to make sure that you have the correct pre-compiled simulation libraries for XE and that the modelsim.ini file is referencing the correct library locations. You can find the latest pre-compiled libraries here:
Another approach to troubleshooting would be to make sure you can perform a behavioral simulation outside of System Generator for DSP. I would create a quick ISE project and see if you can simulate that.
All Xilinx tools should be the same version number. For instance, System Generator 9.2 should be used with ISE 9.2 with all the latest service packs. For details on supported tools for System Generator take a look at answer record 17966: http://www.xilinx.com/support/answers/17966.htm
However I don't believe this is the cause of your errors in this case. It looks as though you haven't compiled the UNISIMS libraries for simulation of Xilinx primitives. To do this go to your Start menu and launch Xilinx ISE > Accessories > Simulation Library Compilation Wizard. Here you'll specify your simulation tool, languages, devices and libraries. It's safe to just select all for compilation.
Well, it's true that i used ModelSim XE at the beginning, but when i had the problem of system generator generating VHDL code and that a mixed mode license is needed, i switched to ModelSim SE or PE as i have a mixed mode license for them.
I'll try compiling the simulation libraries and check.