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My First VPI Program

This page shows a simple VPI program that interacts with a VERILOG code. VPI is the C-Programming interface to the Verilog HDL.

1. The program is tested mainly with free VERILOG simulator - icarus. It has also checked on NCSIM simulator.


2. The VERILOG code is simple. A counter value is decoded and on some value the VPI is called.


3. The VPI program prints the module name; the simulation time and a VERILOG register value. The later use the integer format.


4. The VERILOG new system task invocation is shown below:
   always @ (posedge clk) begin
     if(cnt == 4'd2) begin
       $reg_acc(cnt);
       $display("dbg %d", $time);
     end
   


5. The functional part of the VPI c-code program is shown below:
   static int reg_acc_calltf(char*user_data)
   {
     vpiHandle h1, h2, h3;
     h1 = vpi_handle(vpiSysTfCall, NULL);
     h2 = vpi_iterate(vpiArgument, h1);
     h3 = vpi_scan(h2);
     vpi_printf("the name of the handle is %s\n", vpi_get_str(vpiFullName, h3));
   
     s_vpi_time time;
     time.type = vpiSimTime;
     vpi_get_time(NULL, &time);
     vpi_printf("at %d\n", time.low);
     
     s_vpi_value val;
     val.format = vpiIntVal;
     vpi_get_value (h3, &val);
     vpi_printf("the value is %d\n", val.value.integer);
   
     vpi_free_object(h2);
     return 0;
   }
   


6. The NCSIM simulation is done using the irun utility:
   irun reg_acc.v reg_acc.c vpi_user.c -loadvpi :reg_acc_calltf
   


7. The following bash script is used:
   
   #!/bin/bash
   rm $1.vvp *.vcd
   iverilog-vpi $1.c || exit
   iverilog -o$1.vvp $1.v || exit
   vvp -M. -m$1 $1.vvp || exit
   


8. The output looks like (icarus)
   VCD info: dumpfile vpi.vcd opened for output.
   the name of the handle is cntM.cnt
   at 25
   the value is 2
   dbg 25
   the name of the handle is cntM.cnt
   at 185
   the value is 2
   dbg 185
   the name of the handle is cntM.cnt
   at 345
   the value is 2
   dbg 345
   


9. The entire package, my_first_vpi.tar.gz, is at the download area see below. You can also download it directly from: direct load

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Home	Download Area example of VHDL std_logic_vector to c code string A simple c-code program to read a memory array from verilog RTL, using VPI.