1. Introduction to PLI functions

Verilog PLI(Programming Language Interface) is a mechanism for Verilog code to call C/C++ functions. It enables Verilog to call C/C++ functions written by users like some system calls (e.g. $display/$stop/$random), so that we can start our own system task/function with C/C++ language to realize the inconvenient functions of Verilog and establish contact with the outside world.
PLI can accomplish the following functions:

• Power analysis

• Code Coverage Tool

• Modify Verilog simulation data structure (e.g. change to more precise delay, i.e. sdf inversion)

• Custom Output Display

• Joint simulation

• Debugging function of design

• Simulation analysis

• C Model Interface for Accelerated Simulation

• Testbench Modeling

Verilog PLI provides some access to the internal data structure of verilog

• TF routines: Most of them start with tf_and are mainly used for user-defined operation of system tasks and function variables, tool functions (such as setting callback functions and writing data to output)

• Access routines: Second generation PLI. All begin with acc_ Object-oriented access to SV structure is provided. It is mainly used to access and modify information, which is partly duplicated by delay value, logic value. ACC routines and TF routines.

• VPI routines: Third generation PLI. Most start with vpi_ Object-oriented access to SV structure, behavior, assertion, coverage objects is provided. It contains all the functions of TF and ACC routines.

2. User-defined task/function naming

The rules are as follows:

• The first character must be$

• The remaining characters can be letters, numbers, underscores, or$

• Case-sensitive

• Names can be of any length

3. User-defined task/function parameters

Example:

$get_vector("test_vector.pat", input_bus);

A set of PLI routines can be used in PLI programs to read/write these parameters

4. task/function

• User-defined task can be used anywhere SV task can be used

• User-defined function s can be used anywhere SV task can be used, return values, and the length is determined by user-provided sizetf

5. User-provided PLI application

Such C functions are not independent C programs, but are Link-loaded into tools, which may be called when user-defined task/function is called.

6. PLI include file

Definition

• constant

• struct

• data

These documents are

• vpi_user.h

• sv_vpi_user.h

7. NC Example

Files

test.v

module test;
  wire a, b, c;
  initial
    begin
      $module_info;
    end
  pipe p1 (a, b, c);
  //stimuli
  //monitor response
endmodule

pipe.v

module pipe ( out, in, clk );
  output out; reg out;
  input in, clk;
     always @ (in)
     @ (posedge clk)
    out <= repeat (2) @ (posedge clk) in;
endmodule

mod_info.c

#include <stdio.h>
#include "vpi_user.h"
#include "vpi_user_cds.h"

void module_info()
{
  vpiHandle moditH, topmodH;
  moditH = vpi_iterate(vpiModule, NULL);
  if(!moditH) {
     vpi_printf("    Error: no modules in the design\n");
  }
   while (topmodH = vpi_scan(moditH)) {
    vpi_printf("Top module Full Name: %s\n",
     vpi_get_str(vpiFullName, topmodH));
    vpi_printf(" Top module Name: %s\n", vpi_get_str(vpiName, topmodH));
   }
}
void register_my_systfs()
{
  s_vpi_systf_data task_data_s;
  p_vpi_systf_data task_data_p = &task_data_s;
  task_data_p->type = vpiSysTask;
  task_data_p->tfname = "$module_info";
  task_data_p->calltf = (int(*)()) module_info;
  task_data_p->compiletf = 0;
  vpi_register_systf(task_data_p);
}

pli.map

$module_info call = module_info

vpi_user.c

#include <stdarg.h>
#include "vpi_user.h"
#include "vpi_user_cds.h"

extern void register_my_systfs();

void (*vlog_startup_routines[VPI_MAXARRAY])() =
{
  register_my_systfs,
  0 /*** final entry must be 0 ***/
};

RUN

There are three ways to run on NC, but the first one is not tried.

Method 1 Using the irun Utility

irun test.v pipe.v module_info.c -loadvpi :module_info

Actual measurements will not find $module_info at run time

Method 2 Using a PLI/VPI Map File

The plimap file is shown above.

 irun test.v pipe.v mod_info.c -plimapfile pli.map -gui

Load-plimap file at run time
Or it can be loaded when elab

 irun test.v pipe.v mod_info.c -afile pli.map -gui

Method Three Associating C Functions with a New System Task

• Register your VPI program with C function

• Initialize an s_vpi_systf_data structure

• Call vpi_register_systf()

• Provide the name of the registration function to simulator

typedef struct t_vpi_systf_data
{
  int type;
  int sysfunctype;
  char *tfname;
  int (*calltf)();
  int (*compiletf)();
  int (*sizetf)();
  char *user_data;
} s_vpi_systf_data, *p_vpi_systf_data;

Run the command as follows:

gcc -fPIC -c -o vpi_user.o vpi_user.c mod_info.c -I${IES_HOME}/tools/include -I${IES_HOME}/tools/inca/include
gcc -shared -fPIC -o libvpi.so vpi_user.o

irun -c test.v pipe.v
irun -64bit -R

The tool automatically loads libvpi.so
perhaps

gcc -fPIC -shared -o libmyvpi.so vpi_user.c mod_info.c -I${IES_HOME}/tools/include -I${IES_HOME}/tools/inca/include
ncvlog test.v pipe.v
ncelab -access +rw test -loadvpi libmyvpi:register_my_systfs
ncsim test -input

For PLI, using - sv_lib is not useful

gcc -fPIC -shared -o libmyvpi.so vpi_user.c mod_info.c -I${IES_HOME}/tools/include -I${IES_HOME}/tools/inca/include
irun -c test.v pipe.v
irun -R -64bit -sv_lib libmyvpi.so

Errors will be reported:

irun(64): 15.10-s020: (c) Copyright 1995-2016 Cadence Design Systems, Inc.  
Loading snapshot worklib.test:v .................... Done  
      $module_info;  
                 |  
ncsim: *E,MSSYSTF (./test.v,5|17): User Defined system task or function ($module_info) registered during elaboration and used within the simulation has not been registered during simulation.

Note: Part 7 above is owned by Cadence.