简介

供SV，无论是构建测试激励，或模拟硬件的并行行为，DPI这是非常方便。上次我们介绍SV内通“import”导入和电话C性能。

在本节，通过一个简单的例子来说明C什么语言的函数调用SV的task和function。

1，SV部分

/*

* test.v  Rill create for dpi test at 2014-10-20

*/

`timescale 1ns/1ns

module tb;

   import "DPI-C" context function int c_func(input int num);// or import "DPI-C" context task c_display(input int num);

      reg tmp;

      initial begin

	 #10

	   tmp = c_func(1);

      end

   m1 M1();

   m2 M2();

endmodule // top

module m1;

   import "DPI-C" context function void c_get_m1_scope();

   export "DPI" function m1_add;

   reg tmp;

   reg [7:0] m1_value;

   function int m1_add(input [7:0] num);

      m1_add = num + m1_value; //or return (num + m1_value);

   endfunction // m1_add

   initial begin

      c_get_m1_scope();

      m1_value = 8'd100;

   end

endmodule // m1

module m2;

   import "DPI-C" context function void c_get_m2_scope();

   export "DPI-C" task m2_add;

   reg tmp;

   reg [31:0] m2_value;

   task m2_add(input int num,output int sum);

      sum = num + m2_value;

   endtask // m2_add

   initial begin

      c_get_m2_scope();

      m2_value = 32'd200;

   end

endmodule // m1

2，C部分

/*

* test.c  Rill create for dpi test at 2014-10-20

*/

#include <stdio.h>

#include <svdpi.h>

svScope tmp_scope;

svScope m1_scope;

svScope m2_scope;

//import task/funcs from sv

extern int m1_add();

extern int m2_add();

//==scope switch

void c_get_tmp_scope(void)

{

  tmp_scope = svGetScope();

}

void c_set_tmp_scope(void)

{

  svSetScope(tmp_scope);

}

void c_get_m1_scope(void)

{

  m1_scope = svGetScope();

}

void c_set_m1_scope(void)

{

  svSetScope(m1_scope);

}

void c_get_m2_scope(void)

{

  m2_scope = svGetScope();

}

void c_set_m2_scope(void)

{

  svSetScope(m2_scope);

}

//==export c funcs to sv

int c_func(int num)

{

  int m1 = 0;

  int m2 = 0;

  c_get_tmp_scope();

  c_set_m1_scope();

  m1 = m1_add(num);

  c_set_tmp_scope();

  printf("m1:%d\n",m1);

  c_get_tmp_scope();

  c_set_m2_scope();

  m2_add(num,&m2);

  c_set_tmp_scope();

  printf("m2:%d\n",m2);

  return 0;

}

3，脚本

#! /bin/bash

#

# test.sh

# usage: ./test.sh c/w/r

# Rill create 2014-10-20

#

TOP_MODULE=tb

tcl_file=run.tcl

CDS_INST_DIR=/home/openrisc/opt/edatools/IUS08.20

if [ $# != 1 ];then

echo "args must be c/w/r"

exit 0

fi

if [ $1 == "c" ]; then

echo "compile rtl lib..."

ncvlog -f ./vflist -sv -update -LINEDEBUG;

ncelab -delay_mode zero -access +rwc -timescale 1ns/10ps ${TOP_MODULE}

echo "compile dpi lib"

if [ -e libdpi.so ];then

rm libdpi.so -f

fi

gcc -fPIC -shared -o libdpi.so test.c -I$CDS_INST_DIR/tools/inca/include

exit 0

fi

if [ -e ${tcl_file} ];then

rm ${tcl_file} -f

fi

touch ${tcl_file}

if [ $1 == "w" ];then

echo "open wave..."

echo "database -open waves -into waves.shm -default;" >> ${tcl_file}

echo "probe -shm -variable -all -depth all;" >> ${tcl_file}

echo "run" >> ${tcl_file}

echo "exit" >> ${tcl_file}

fi

if [ $1 == "w" -o $1 == "r" ];then

echo "sim start..."

ncsim  ${TOP_MODULE} -input ${tcl_file}

fi

echo "$(date) sim done!"

4，说明

细致体会我们上面构造的样例，有几个问题须要弄清楚。

a。scope的含义：

在SV端。m1是不能直接调用m2中的task/function的。所以m1里面调用的C函数也不能直接调用m2中export出来的task/function。假设想调用，必须进行scope切换。

b。SV端，有task和function的区分。可是在C端，并没有区分，一律是C函数。

5，关于用C模拟硬件的并行行为

方式a，将流水后面的模块写在前面。这样的方式我们之前介绍过（http://blog.csdn.net/rill_zhen/article/details/8464930），这里不再赘述。

方式b，将全部并行的信号写成例如以下形式：

用c,n两个变量模拟reg的值。

用init和update两个函数模拟reg的行为。

/*

* parallel.c  Rill create for simulater test at 2014-10-20

*/

struct signal;

struct sig_ops

{

	int (*init) (struct signal*);

	int (*update) (struct signal*);

};

struct signal

{

	unsigned int c; //current cycle value

	unsigned int n; //next cycle value

	char name[32];

	struct sig_ops* ops;

};

/* veritual functions

int sig_init(struct signal* signal)

{

	return signal->ops->init(signal);

}

int sig_update(struct signal* signal)

{

	return signal->ops->update(signal);

}

*/

//actual functions

int test_init(struct signal* signal)

{

	signal->c = 0;

	signal->n = 0;

	return 0;

}

int test_update(struct signal* signal)

{

	signal->c = signal->n;

	return 0;

}

int signal_create(struct signal* signal,char * name)

{

	signal->name = name;

}

//============main.c====================//

//example signal

struct signal test;

struct sig_ops test_ops =

{

	test_init,

	test_update,

};

int main()

{

	signal_create(&test,"test");

	//when reset

	test->ops->init(&test);

	//per cycle

	test->ops->update(&test);

	return 0;

}