I had downloaded SDRAM controller code from xilinx web. the code use
unisim library. where can I get the unisim library? or in other way how can I simulate the code using Modelsim.
Check your xilinx installation folder first. Unisims can be found at
<xilinx>/verilog/src/unisims
or
<xilinx>/vhdl/src/unisims
depending on the HDL used