ModelSim error: Instantiation of 'OR' failed

Question

I am having trouble with running a Verilog project with ModelSim Student Edition 10.2c. Everything compiles without error, however I get the following error at runtime:

# vsim -gui work.testbench 
# Loading work.testbench
# Loading work.circuit1_assign
# ** Error: (vsim-3033) C:/Modeltech_pe_edu_10.2c/examples/circuit1_assign.v(14): Instantiation of 'OR' failed. The design unit was not found.
# 
#         Region: /testbench/c
#         Searched libraries:
#             C:/Modeltech_pe_edu_10.2c/examples/hw4
# ** Error: (vsim-3033) C:/Modeltech_pe_edu_10.2c/examples/circuit1_assign.v(16): Instantiation of 'NOT' failed. The design unit was not found.
# 
#         Region: /testbench/c
#         Searched libraries:
#             C:/Modeltech_pe_edu_10.2c/examples/hw4
# ** Error: (vsim-3033) C:/Modeltech_pe_edu_10.2c/examples/circuit1_assign.v(18): Instantiation of 'AND' failed. The design unit was not found.
# 
#         Region: /testbench/c
#         Searched libraries:
#             C:/Modeltech_pe_edu_10.2c/examples/hw4
# Loading work.t1
# Error loading design

I have no idea what this means. I think this is a simple mistake I am making, but I cannot resolve it. Does anybody know what I can do so that my project will work?

I believe this has to do with the inability to include the file where AND, OR and NOT are defined. After googling, I found that the file modelsim.ini must be placed in the project directory. However, I have placed modelsim.ini in the correct directory, yet it still does not work.

I have posted all three source files for my project (which is simply testing a combinational circuit). Here is my code for circuit1_assign.v:

module circuit1_assign
  (
    input x,
    
    input y,
    
    input z,
    
    output f
  );
  
  wire w1, w2;
  
  OR  o1 (.i0(x), .i1(y), .o(w1));
  
  NOT n1 (.i2(z), .o(w2));
  
  AND a1 (.i3(w1), .i4(w2), .o(f));
  
endmodule

Here is code for a test:

`timescale 1ns/1ps

module t1
  (
    output reg a,
    output reg b,
    output reg c
  );
    
    initial
      begin
          a = 0;        //Do all combinations of possible input values    
          b = 0;
          c = 0;
          #10 a = 0;
          #10 b = 0;
          #10 c = 1;
          #10 a = 0;
          #10 b = 1;
          #10 c = 0;
          #10 a = 0;
          #10 b = 1;
          #10 c = 1;
          #10 a = 1;
          #10 b = 0;
          #10 c = 0;
          #10 a = 1;
          #10 b = 0;
          #10 c = 1;
          #10 a = 1;
          #10 b = 1;
          #10 c = 0;
          #10 a = 1;
          #10 b = 1;
          #10 c = 1;
          #10 $finish;
      end
    endmodule

Here is my code for the testbench:

`timescale 1ns/1ps
module testbench();
    wire l, m, n, o;
    
    circuit1_assign c
    (
      .x (l),
      .y (m),
      .z (n),
      .f (o)
    );
    
    t1 t
    (
      .a (l),
      .b (m),
      .c (n)
    );
    
    initial 
    begin
      $monitor ($time,,"l=%b, m=%b, n=%b, o=%b",
                      l, m, n, o);
  end      
endmodule

score 4 · Accepted Answer · answered Nov 25 '13 at 16:55

4

Have you tried using lowercase gates (and, or, etc)?

In every example of gate level modelling in verilog I have seen these primitives in lowercase, not uppercase.

See: http://www.asic-world.com/verilog/gate1.html

answered Nov 25 '13 at 16:55

Tim

35,413
11
95
121

score 1 · Answer 2 · answered Nov 25 '13 at 14:41

1

Your circuit1_assign is instantiating other modules called OR, NOT, AND. The tools are looking for those modules, but it cannot find them, so it throws an error. If you want to use those modules, you'll need to create them yourself. Otherwise, you can use assign statements in Verilog to accomplish your goal. You can change circuit1_assign to this:

assign w1 = x | y;
assign w2 = ~z;  //I think this is right?  
assign f  = w1 & w2;

answered Nov 25 '13 at 14:41

Russell

3,384
4
31
45

`AND`, `OR`, and `NOT` are not included in some standard header? – CodeKingPlusPlus Nov 25 '13 at 14:45
@CodeKingPlusPlus Not the way that you wrote them. The way I have them in the answer above is the bit-wise and, or, and not functionality that you are looking for. These symbols are built into Verilog. The way you wrote it implies that you do not want to use any built in constructs, instead it's telling the tools to go look for some 3rd party modules called AND, OR, and NOT. – Russell Nov 25 '13 at 15:33

ModelSim error: Instantiation of 'OR' failed

2 Answers2