前言：验证结构与实验3是相同的，但需要验证的对象是完整的mcdf。对比之前新添加了reg寄存器模块（选择数据），formatter模块（数据打包）。

种一棵树最好的时间是十年前，其次是现在。不是吗？

1. 实验3结构包含moinitor、checker、generator、initiator、test，这已经是一个完整的仿真结构，实验4可以说是实验3结构的复制粘贴。
2. 实验4将设计变得更复杂，添加了reg寄存器模块，formatter模块。验证过程完全相同，需要像实验3的验证过程一样对这两个模块也做仿真验证。
   设计中reg的功能是可以选择从哪个fifo接收数据，并且可以判断fifo余量（之前是margin），可以控制打包的长度。formatter做数据打包。

在实验4，理解整个验证结构组成，理解各个package。类比实验3来学习实验4。
关于实验代码、验证相关的资料，你找的到的找不到的都可以从公众号"袁小丑"免费获取！

结构框图

• chnl_agent与之前相比是完全相同的。
• reg模块通过reg_interface与负责测试reg的 reg_agent连接。
• formatter通过Formater_interface与负责测试它的fomatter_agent完成连接。
• mcdf_env顶层环境包括chnl_agent、reg_agent、fomatter_agent和checker。
• 左边橘黄色是test的部分，对mcdf_env、generator例化，发送数据。

每个package负责验证一个模块。

1. reg_pkg

• reg这个模块用来发送寄存器的配置。
• 包括trans激励的类型、driver发送激励、generator产生激励、monitor检测激励、agent将mon和driver包在一起。激励也就是发送的数据。

`include "param_def.v"//定义宏，比如定义SLV0_RW_ADDR的具体值，修改值只需要修改宏。

package reg_pkg;

1.1 reg_trans

  class reg_trans;
    rand bit[7:0] addr;//哪个寄存器
    rand bit[1:0] cmd;//读写
    rand bit[31:0] data;//数据内容
    bit rsp;//判断读写是否正常

1.11 寄存器约束

    constraint cstr {
      soft cmd inside {`WRITE, `READ, `IDLE};//读还是写引用定义
      soft addr inside {`SLV0_RW_ADDR, `SLV1_RW_ADDR, `SLV2_R_ADDR, `SLV0_R_ADDR, `SLV1_R_ADDR, `SLV2_R_ADDR};//3个读地址，3个写地址
      addr[7:4]==0 && cmd==`WRITE -> soft data[31:6]==0;
      soft addr[7:5]==0;
      addr[4]==1 -> soft cmd == `READ;//表示只读寄存器
    };

在 mcdf说明文档中寄存器的地址有00、04、08、10、14和18。这6中，用二进制表示为0000_0000、0000_0100、0000_1000、0001_0000、0001_0100、0001_1000。

• 当高4位为0，即addr[7:4]为0，为读写寄存器，如果是写操作，让保留位即不能更改的位置，置0。
• 第4位为1表示只读寄存器，此时的cmd为read。
• 数据地址的高三位为0。

读写寄存器

• bit(0)：通道使能信号。1为打开，0位关闭。复位值为1。 bit(2:1)：优先级。0为最高，3为最低。复位值为3。

• bit(5:3)：数据包长度，解码对应表为，
  0对应长度4，1对应长度8，2对应长度16，3对应长度32，其它数值（4-7）均暂时对应长度32。复位值为0。

• bit(31:6)：保留位，无法写入。复位值为0。

只读寄存器

bit(7:0)：上行数据从端FIFO的可写余量，同FIFO的数据余量保持同步变化。复位值为FIFO的深度数。
bit(31:8)：保留位，复位值为0。

1.12 clone、sprint、

    function reg_trans clone();
      reg_trans c = new();
      c.addr = this.addr;
      c.cmd = this.cmd;
      c.data = this.data;
      c.rsp = this.rsp;
      return c;
    endfunction

   function string sprint();
      string s;
      s = {s, $sformatf("=======================================\n")};
      s = {s, $sformatf("reg_trans object content is as below: \n")};
      s = {s, $sformatf("addr = %2x: \n", this.addr)};
      s = {s, $sformatf("cmd = %2b: \n", this.cmd)};
      s = {s, $sformatf("data = %8x: \n", this.data)};
      s = {s, $sformatf("rsp = %0d: \n", this.rsp)};
      s = {s, $sformatf("=======================================\n")};
      return s;
    endfunction
  endclass

1.2 reg_driver

  class reg_driver;
    local string name;
    local virtual reg_intf intf;
    mailbox #(reg_trans) req_mb;
    mailbox #(reg_trans) rsp_mb;

    function new(string name = "reg_driver");
      this.name = name;
    endfunction
  
    function void set_interface(virtual reg_intf intf);
      if(intf == null)
        $error("interface handle is NULL, please check if target interface has been intantiated");
      else
        this.intf = intf;
    endfunction

    task run();
      fork
        this.do_drive();
        this.do_reset();
      join
    endtask

    task do_reset(); //复位
      forever begin
        @(negedge intf.rstn);
        intf.cmd_addr <= 0;
        intf.cmd <= `IDLE;
        intf.cmd_data_m2s <= 0;
      end
    endtask

    task do_drive();
      reg_trans req, rsp;
      @(posedge intf.rstn);
      forever begin
        this.req_mb.get(req);
        this.reg_write(req);
        rsp = req.clone();
        rsp.rsp = 1;
        this.rsp_mb.put(rsp);
      end
    endtask
  
    task reg_write(reg_trans t);//给寄存器
      @(posedge intf.clk iff intf.rstn);
      case(t.cmd)
        `WRITE: begin //如果是写操作
                  intf.drv_ck.cmd_addr <= t.addr; //地址
                  intf.drv_ck.cmd <= t.cmd; 
                  intf.drv_ck.cmd_data_m2s <= t.data; //数据
                end
        `READ:  begin 
                  intf.drv_ck.cmd_addr <= t.addr; //总线
                  intf.drv_ck.cmd <= t.cmd; 
                  repeat(2) @(negedge intf.clk);//等两个时钟的下降沿，第一个下降沿还在
                  t.data = intf.cmd_data_s2m; //采样了intf的数据
                end
        `IDLE:  begin 
                  this.reg_idle(); //等一拍
                end
        default: $error("command %b is illegal", t.cmd);
      endcase
      $display("%0t reg driver [%s] sent addr %2x, cmd %2b, data %8x", $time, name, t.addr, t.cmd, t.data);
    endtask

当case为 READ时，等待了两个时钟的下降沿。
第一个下降沿还在当前周期，第二个下降沿就在下一个周期了。此时数据已经驱动到接口cmd_data_s2m处了，这时去采样接口处的数据就一定是要读的数据。

• 在控制寄存器接口上，需要在每一个时钟解析cmd。当cmd为写（WR）指令时，需要把数据cmd_data_in写入到cmd_addr对应的寄存器中；当cmd为读指令(RD)时，即需要从cmd_addr对应的寄存器中读取数据，并在下一个周期，将数据驱动至cmd_data_out接口。

    task reg_idle();
      @(posedge intf.clk);
      intf.drv_ck.cmd_addr <= 0;
      intf.drv_ck.cmd <= `IDLE;
      intf.drv_ck.cmd_data_m2s <= 0;
    endtask
  endclass

1.3 reg_generator

  class reg_generator;
    rand bit[7:0] addr = -1;
    rand bit[1:0] cmd = -1;
    rand bit[31:0] data = -1;

    mailbox #(reg_trans) req_mb;
    mailbox #(reg_trans) rsp_mb;

    reg_trans reg_req[$];

    constraint cstr{
      soft addr == -1;
      soft cmd == -1;
      soft data == -1;
    }

    function new();
      this.req_mb = new();
      this.rsp_mb = new();
    endfunction

    task start();
      send_trans();
    endtask

    // generate transaction and put into local mailbox
    task send_trans();
      reg_trans req, rsp;//做例化
      req = new();
      assert(req.randomize with {local::addr >= 0 -> addr == local::addr;
                                 local::cmd >= 0 -> cmd == local::cmd;
                                 local::data >= 0 -> data == local::data;
                               })
        else $fatal("[RNDFAIL] register packet randomization failure!");
      $display(req.sprint());
      this.req_mb.put(req);//放入数据
      this.rsp_mb.get(rsp);
      $display(rsp.sprint());
      if(req.cmd == `READ) 
        this.data = rsp.data;
      assert(rsp.rsp)
        else $error("[RSPERR] %0t error response received!", $time);
    endtask

    function string sprint();
      string s;
      s = {s, $sformatf("=======================================\n")};
      s = {s, $sformatf("reg_generator object content is as below: \n")};
      s = {s, $sformatf("addr = %2x: \n", this.addr)};
      s = {s, $sformatf("cmd = %2b: \n", this.cmd)};
      s = {s, $sformatf("data = %8x: \n", this.data)};
      s = {s, $sformatf("=======================================\n")};
      return s;
    endfunction

    function void post_randomize();
      string s;
      s = {"AFTER RANDOMIZATION \n", this.sprint()};
      $display(s);
    endfunction
  endclass

  class reg_monitor;
    local string name;
    local virtual reg_intf intf;
    mailbox #(reg_trans) mon_mb;
    function new(string name="reg_monitor");
      this.name = name;
    endfunction
    function void set_interface(virtual reg_intf intf);
      if(intf == null)
        $error("interface handle is NULL, please check if target interface has been intantiated");
      else
        this.intf = intf;
    endfunction
    task run();
      this.mon_trans();
    endtask

    task mon_trans();
      reg_trans m;
      forever begin
        @(posedge intf.clk iff (intf.rstn && intf.mon_ck.cmd != `IDLE));//时钟的上升沿，并且数据合理
        m = new();//生成一个对象，把数据地址放入
        m.addr = intf.mon_ck.cmd_addr;
        m.cmd = intf.mon_ck.cmd;
        if(intf.mon_ck.cmd == `WRITE) begin//写指令，把总线上的数据放入
          m.data = intf.mon_ck.cmd_data_m2s;
        end
        else if(intf.mon_ck.cmd == `READ) begin//读指令，等下一个周期，再放入数据
          @(posedge intf.clk);
          m.data = intf.mon_ck.cmd_data_s2m;
        end
        mon_mb.put(m);//把数据交给checker
        $display("%0t %s monitored addr %2x, cmd %2b, data %8x", $time, this.name, m.addr, m.cmd, m.data);
      end
    endtask
  endclass

1.4 reg_agent

  class reg_agent;//包含了monitor，driver，让driver，monitor工作起来
    local string name;
    reg_driver driver;
    reg_monitor monitor;
    local virtual reg_intf vif;
    function new(string name = "reg_agent");
      this.name = name;
      this.driver = new({name, ".driver"});
      this.monitor = new({name, ".monitor"});
    endfunction

    function void set_interface(virtual reg_intf vif);
      this.vif = vif;
      driver.set_interface(vif);
      monitor.set_interface(vif);
    endfunction
    task run();
      fork
        driver.run();
        monitor.run();
      join
    endtask
  endclass

激励的类型、发送激励、产生激励、检测激励、agent

2. fmt_apk

chnl和reg的driver都是主动的发送数据给dut，而fmt的driver是被动的接受发送出来的数据。所以fmt像一个fifo，储存发送出来的数据。
需要设计fifo的大小宽度，来储存发送出来的数据。

package fmt_pkg;
  import rpt_pkg::*;
//传出来的数据可能有不同的带宽、需要的fifo大小也不同，把可能需要的都枚举出来。
  typedef enum {SHORT_FIFO, MED_FIFO, LONG_FIFO, ULTRA_FIFO} fmt_fifo_t;
  typedef enum {LOW_WIDTH, MED_WIDTH, HIGH_WIDTH, ULTRA_WIDTH} fmt_bandwidth_t;

2.1 fmt_trans

  class fmt_trans;
    rand fmt_fifo_t fifo;
    rand fmt_bandwidth_t bandwidth;
    bit [9:0] length;
    bit [31:0] data[];
    bit [1:0] ch_id;
    bit rsp;
    constraint cstr{
      soft fifo == MED_FIFO;//fifo
      soft bandwidth == MED_WIDTH;//带宽
    };
    function fmt_trans clone();
      fmt_trans c = new();
      c.fifo = this.fifo;
      c.bandwidth = this.bandwidth;
      c.length = this.length;
      c.data = this.data;
      c.ch_id = this.ch_id;
      c.rsp = this.rsp;
      return c;
    endfunction

    function string sprint();
      string s;
      s = {s, $sformatf("=======================================\n")};
      s = {s, $sformatf("fmt_trans object content is as below: \n")};
      s = {s, $sformatf("fifo = %s: \n", this.fifo)};
      s = {s, $sformatf("bandwidth = %s: \n", this.bandwidth)};
      s = {s, $sformatf("length = %s: \n", this.length)};
      foreach(data[i]) s = {s, $sformatf("data[%0d] = %8x \n", i, this.data[i])};
      s = {s, $sformatf("ch_id = %0d: \n", this.ch_id)};
      s = {s, $sformatf("rsp = %0d: \n", this.rsp)};
      s = {s, $sformatf("=======================================\n")};
      return s;
    endfunction

    function bit compare(fmt_trans t);//当前的与传进来的数作比较
      string s;
      compare = 1;
      s = "\n=======================================\n";
      s = {s, $sformatf("COMPARING fmt_trans object at time %0d \n", $time)};
      if(this.length != t.length) begin
        compare = 0;
        s = {s, $sformatf("sobj length %0d != tobj length %0d \n", this.length, t.length)};
      end
      if(this.ch_id != t.ch_id) begin
        compare = 0;
        s = {s, $sformatf("sobj ch_id %0d != tobj ch_id %0d\n", this.ch_id, t.ch_id)};
      end
      foreach(this.data[i]) begin
        if(this.data[i] != t.data[i]) begin
          compare = 0;
          s = {s, $sformatf("sobj data[%0d] %8x != tobj data[%0d] %8x\n", i, this.data[i], i, t.data[i])};
        end
      end
      if(compare == 1) s = {s, "COMPARED SUCCESS!\n"};
      else  s = {s, "COMPARED FAILURE!\n"};
      s = {s, "=======================================\n"};
      rpt_pkg::rpt_msg("[CMPOBJ]", s, rpt_pkg::INFO, rpt_pkg::MEDIUM);
    endfunction
  endclass

2.2 fmt_driver

  class fmt_driver;
    local string name;
    local virtual fmt_intf intf;
    mailbox #(fmt_trans) req_mb;
    mailbox #(fmt_trans) rsp_mb;

    local mailbox #(bit[31:0]) fifo;
    local int fifo_bound;//长度
    local int data_consum_peroid;//消耗周期，侧面反应带宽，带宽越大，消耗周期越短

  
    function new(string name = "fmt_driver");
      this.name = name;
      this.fifo = new();//fifo初始化
      this.fifo_bound = 4096;
      this.data_consum_peroid = 1;
    endfunction
  
    function void set_interface(virtual fmt_intf intf);
      if(intf == null)
        $error("interface handle is NULL, please check if target interface has been intantiated");
      else
        this.intf = intf;
    endfunction

    task run();
      fork
        this.do_receive();
        this.do_consume();
        this.do_config();
        this.do_reset();
      join
    endtask
//配置fifo长或者短，消耗数据快还是慢
    task do_config();//配置driver，配置完成后重新例化fifo
      fmt_trans req, rsp;
      forever begin
        this.req_mb.get(req);
        case(req.fifo)//配置为不同长度
          SHORT_FIFO: this.fifo_bound = 64;
          MED_FIFO: this.fifo_bound = 256;
          LONG_FIFO: this.fifo_bound = 512;
          ULTRA_FIFO: this.fifo_bound = 2048;
        endcase
        this.fifo = new(this.fifo_bound);//重新例化，并且规定长度
        case(req.bandwidth)
          LOW_WIDTH: this.data_consum_peroid = 8;
          MED_WIDTH: this.data_consum_peroid = 4;
          HIGH_WIDTH: this.data_consum_peroid = 2;
          ULTRA_WIDTH: this.data_consum_peroid = 1;
        endcase
        rsp = req.clone();
        rsp.rsp = 1;
        this.rsp_mb.put(rsp);
      end
    endtask

    task do_reset(); 
      forever begin
        @(negedge intf.rstn) 
        intf.fmt_grant <= 0;
      end
    endtask

    task do_receive();//模拟从formater接受数据
      forever begin
        @(posedge intf.fmt_req);//fmt的req拉高
        forever begin
          @(posedge intf.clk);//等待一拍
          if((this.fifo_bound-this.fifo.num()) >= intf.fmt_length)//fifo最大容量-已经存放了多少>=即将存放的数据长度
            break;
        end
        intf.drv_ck.fmt_grant <= 1;//可以存放数据，让grant为1
        @(posedge intf.fmt_start);
        fork
          begin
            @(posedge intf.clk);
            intf.drv_ck.fmt_grant <= 0;//过一拍置0
          end
        join_none
        repeat(intf.fmt_length) begin//把传进来的数据在每一拍做采样，重复采样length次。
          @(negedge intf.clk);
          this.fifo.put(intf.fmt_data);
        end
      end
    endtask

    task do_consume();//不断的消耗数据，每过一拍拿一组数据
      bit[31:0] data;
      forever begin
        void'(this.fifo.try_get(data));
        repeat($urandom_range(1, this.data_consum_peroid)) @(posedge intf.clk);
      end
    endtask
  endclass

2.3 fmt_generator

  class fmt_generator;
    rand fmt_fifo_t fifo = MED_FIFO;
    rand fmt_bandwidth_t bandwidth = MED_WIDTH;

    mailbox #(fmt_trans) req_mb;
    mailbox #(fmt_trans) rsp_mb;

    constraint cstr{
      soft fifo == MED_FIFO;
      soft bandwidth == MED_WIDTH;
    }

    function new();
      this.req_mb = new();
      this.rsp_mb = new();
    endfunction

    task start();
      send_trans();
    endtask

    // generate transaction and put into local mailbox
    task send_trans();
      fmt_trans req, rsp;
      req = new();
      assert(req.randomize with {local::fifo != MED_FIFO -> fifo == local::fifo; 
                                 local::bandwidth != MED_WIDTH -> bandwidth == local::bandwidth;
                               })
        else $fatal("[RNDFAIL] formatter packet randomization failure!");
      $display(req.sprint());
      this.req_mb.put(req);
      this.rsp_mb.get(rsp);
      $display(rsp.sprint());
      assert(rsp.rsp)
        else $error("[RSPERR] %0t error response received!", $time);
    endtask

    function string sprint();
      string s;
      s = {s, $sformatf("=======================================\n")};
      s = {s, $sformatf("fmt_generator object content is as below: \n")};
      s = {s, $sformatf("fifo = %s: \n", this.fifo)};
      s = {s, $sformatf("bandwidth = %s: \n", this.bandwidth)};
      s = {s, $sformatf("=======================================\n")};
      return s;
    endfunction

    function void post_randomize();
      string s;
      s = {"AFTER RANDOMIZATION \n", this.sprint()};
      $display(s);
    endfunction

  endclass

2.4 fmt_monitor

  class fmt_monitor;
    local string name;
    local virtual fmt_intf intf;
    mailbox #(fmt_trans) mon_mb;
    function new(string name="fmt_monitor");
      this.name = name;
    endfunction
    function void set_interface(virtual fmt_intf intf);
      if(intf == null)
        $error("interface handle is NULL, please check if target interface has been intantiated");
      else
        this.intf = intf;
    endfunction

    task run();
      this.mon_trans();
    endtask

    task mon_trans();
      fmt_trans m;
      string s;
      forever begin
        @(posedge intf.mon_ck.fmt_start);//假定协议是正常的
        m = new();
        m.length = intf.mon_ck.fmt_length;
        m.ch_id = intf.mon_ck.fmt_chid;
        m.data = new[m.length];
        foreach(m.data[i]) begin
          @(posedge intf.clk);
          m.data[i] = intf.mon_ck.fmt_data;//每一次数据来的时候，都存放在动态数组
        end
        mon_mb.put(m);//放好数据后，放入信箱
        s = $sformatf("=======================================\n");
        s = {s, $sformatf("%0t %s monitored a packet: \n", $time, this.name)};
        s = {s, $sformatf("length = %0d: \n", m.length)};
        s = {s, $sformatf("chid = %0d: \n", m.ch_id)};
        foreach(m.data[i]) s = {s, $sformatf("data[%0d] = %8x \n", i, m.data[i])};
        s = {s, $sformatf("=======================================\n")};
        $display(s);
      end
    endtask
  endclass

2.5 fmt_agent

  class fmt_agent;
    local string name;
    fmt_driver driver;
    fmt_monitor monitor;
    local virtual fmt_intf vif;
    function new(string name = "fmt_agent");
      this.name = name;
      this.driver = new({name, ".driver"});
      this.monitor = new({name, ".monitor"});
    endfunction

    function void set_interface(virtual fmt_intf vif);
      this.vif = vif;
      driver.set_interface(vif);
      monitor.set_interface(vif);
    endfunction
    task run();
      fork
        driver.run();
        monitor.run();
      join
    endtask
  endclass

endpackage

3. checker

• 检测到的数据传到checker，3个chnl、fmt、reg的数据都会存放在checke已经例化好的信箱里。而fmt和3个chnl的数据格式是完全不同的。fmt对数据进行了打包，把数据整合成了新格式。
• 所以比较输入输出先要把chnl、reg的数据需要先整形转化，模拟mcdf的行为。模拟打包后再进行数据的比较。
• refmod利用句柄把数据拿出来，模拟硬件对数据打包。从chnl拿数据，按照长度的不同把数据放入三个输出端。

其中：

• doreset对寄存器复位，清空信箱中的数据。
• doregupdate更新checker中寄存器的配置。
• dopackage对三个chnl做打包。

包含了checker、env和test。

`include "param_def.v"

package mcdf_pkg;

  import chnl_pkg::*;
  import reg_pkg::*;
  import arb_pkg::*;
  import fmt_pkg::*;
  import rpt_pkg::*;

  typedef struct packed {
    bit[2:0] len; //长度
    bit[1:0] prio;//
    bit en;//fifo使能
    bit[7:0] avail;//表示fifo可选余量 
  } mcdf_reg_t;
 
  typedef enum {RW_LEN, RW_PRIO, RW_EN, RD_AVAIL} mcdf_field_t;

3.1 mcdf_refmod

模拟mcdf的功能接受寄存器的读写行为，对检测来的数据进行打包。

  class mcdf_refmod;//模拟mcdf的功能接受寄存器的读写行为，对数据进行打包
    local virtual mcdf_intf intf;
    local string name;
    mcdf_reg_t regs[3];
    mailbox #(reg_trans) reg_mb;
    mailbox #(mon_data_t) in_mbs[3];
    mailbox #(fmt_trans) out_mbs[3];

    function new(string name="mcdf_refmod");
      this.name = name;
      foreach(this.out_mbs[i]) this.out_mbs[i] = new();
    endfunction

    task run();
      fork
        do_reset();
        this.do_reg_update();//模拟寄存器
        do_packet(0);
        do_packet(1);
        do_packet(2);
      join
    endtask

    task do_reg_update();//硬件上对寄存器的读写更新到仿真中
      reg_trans t;//引用regtrans里的数据
      forever begin
        this.reg_mb.get(t);
        if(t.addr[7:4] == 0 && t.cmd == `WRITE) begin
          this.regs[t.addr[3:2]].en = t.data[0];
          this.regs[t.addr[3:2]].prio = t.data[2:1];
          this.regs[t.addr[3:2]].len = t.data[5:3];
        end
        else if(t.addr[7:4] == 1 && t.cmd == `READ) begin
          this.regs[t.addr[3:2]].avail = t.data[7:0];
        end
      end
    endtask

    task do_packet(int id);//把chnl的数据打包
      fmt_trans ot; 
      mon_data_t it;
      forever begin
        this.in_mbs[id].peek(it);
        ot = new();
        ot.length = 4 << (this.get_field_value(id, RW_LEN) & 'b11);//拿到打包的长度
        ot.data = new[ot.length];//开辟空间
        ot.ch_id = id;
        foreach(ot.data[m]) begin//拿完数据，把ot放到对应的信箱。
          this.in_mbs[id].get(it);
          ot.data[m] = it.data;
        end
        this.out_mbs[id].put(ot);
      end
    endtask

    function int get_field_value(int id, mcdf_field_t f);
      case(f)
        RW_LEN: return regs[id].len;
        RW_PRIO: return regs[id].prio;
        RW_EN: return regs[id].en;
        RD_AVAIL: return regs[id].avail;
      endcase
    endfunction 

    task do_reset();//寄存器复位
      forever begin
        @(negedge intf.rstn); 
        foreach(regs[i]) begin
          regs[i].len = 'h0;
          regs[i].prio = 'h3;
          regs[i].en = 'h1;
          regs[i].avail = 'h20;
        end
      end
    endtask

    function void set_interface(virtual mcdf_intf intf);
      if(intf == null)
        $error("interface handle is NULL, please check if target interface has been intantiated");
      else
        this.intf = intf;
    endfunction
    
  endclass
## 3.2 mcdf_checker
```java
  class mcdf_checker;
    local string name;
    local int err_count;
    local int total_count;
    local int chnl_count[3];
    local virtual mcdf_intf intf;
    local mcdf_refmod refmod;
    mailbox #(mon_data_t) chnl_mbs[3];
    mailbox #(fmt_trans) fmt_mb;
    mailbox #(reg_trans) reg_mb;
    mailbox #(fmt_trans) exp_mbs[3];

    function new(string name="mcdf_checker");
      this.name = name;
      foreach(this.chnl_mbs[i]) this.chnl_mbs[i] = new();
      this.fmt_mb = new();
      this.reg_mb = new();
      this.refmod = new();
      foreach(this.refmod.in_mbs[i]) begin
        this.refmod.in_mbs[i] = this.chnl_mbs[i];
        this.exp_mbs[i] = this.refmod.out_mbs[i];
      end
      this.refmod.reg_mb = this.reg_mb;
      this.err_count = 0;
      this.total_count = 0;
      foreach(this.chnl_count[i]) this.chnl_count[i] = 0;
    endfunction

    function void set_interface(virtual mcdf_intf intf);
      if(intf == null)
        $error("interface handle is NULL, please check if target interface has been intantiated");
      else
        this.intf = intf;
        this.refmod.set_interface(intf);
    endfunction

    task run();
      fork
        this.do_compare();
        this.refmod.run();
      join
    endtask

    task do_compare();
      fmt_trans expt, mont;
      bit cmp;
      forever begin
        this.fmt_mb.get(mont);
        this.exp_mbs[mont.ch_id].get(expt);
        cmp = mont.compare(expt);   
        this.total_count++;
        this.chnl_count[mont.ch_id]++;
        if(cmp == 0) begin
          this.err_count++;
          rpt_pkg::rpt_msg("[CMPFAIL]", 
            $sformatf("%0t %0dth times comparing but failed! MCDF monitored output packet is different with reference model output", $time, this.total_count),
            rpt_pkg::ERROR,
            rpt_pkg::TOP,
            rpt_pkg::LOG);
        end
        else begin
          rpt_pkg::rpt_msg("[CMPSUCD]",
            $sformatf("%0t %0dth times comparing and succeeded! MCDF monitored output packet is the same with reference model output", $time, this.total_count),
            rpt_pkg::INFO,
            rpt_pkg::HIGH);
        end
      end
    endtask

    function void do_report();
      string s;
      s = "\n---------------------------------------------------------------\n";
      s = {s, "CHECKER SUMMARY \n"}; 
      s = {s, $sformatf("total comparison count: %0d \n", this.total_count)}; 
      foreach(this.chnl_count[i]) s = {s, $sformatf(" channel[%0d] comparison count: %0d \n", i, this.chnl_count[i])};
      s = {s, $sformatf("total error count: %0d \n", this.err_count)}; 
      foreach(this.chnl_mbs[i]) begin
        if(this.chnl_mbs[i].num() != 0)
          s = {s, $sformatf("WARNING:: chnl_mbs[%0d] is not empty! size = %0d \n", i, this.chnl_mbs[i].num())}; 
      end
      if(this.fmt_mb.num() != 0)
          s = {s, $sformatf("WARNING:: fmt_mb is not empty! size = %0d \n", this.fmt_mb.num())}; 
      s = {s, "---------------------------------------------------------------\n"};
      rpt_pkg::rpt_msg($sformatf("[%s]",this.name), s, rpt_pkg::INFO, rpt_pkg::TOP);
    endfunction
  endclass

3.2 mcdf_env

  class mcdf_env;
    chnl_agent chnl_agts[3];
    reg_agent reg_agt;
    fmt_agent fmt_agt;
    mcdf_checker chker;
    protected string name;

    function new(string name = "mcdf_env");//做例化和连接
      this.name = name;
      this.chker = new();
      foreach(chnl_agts[i]) begin
        this.chnl_agts[i] = new($sformatf("chnl_agts[%0d]",i));
        this.chnl_agts[i].monitor.mon_mb = this.chker.chnl_mbs[i];
      end
      this.reg_agt = new("reg_agt");
      this.reg_agt.monitor.mon_mb = this.chker.reg_mb;
      this.fmt_agt = new("fmt_agt");
      this.fmt_agt.monitor.mon_mb = this.chker.fmt_mb;
      $display("%s instantiated and connected objects", this.name);
    endfunction

    virtual task run();
      $display($sformatf("*****************%s started********************", this.name));
      this.do_config();
      fork
        this.chnl_agts[0].run();
        this.chnl_agts[1].run();
        this.chnl_agts[2].run();
        this.reg_agt.run();
        this.fmt_agt.run();
        this.chker.run();
      join
    endtask

    virtual function void do_config();
    endfunction

    virtual function void do_report();
      this.chker.do_report();
    endfunction

  endclass

3.3 test

  class mcdf_base_test;
    chnl_generator chnl_gens[3];
    reg_generator reg_gen;
    fmt_generator fmt_gen;
    mcdf_env env;
    protected string name;

    function new(string name = "mcdf_base_test");
      this.name = name;
      this.env = new("env");

      foreach(this.chnl_gens[i]) begin
        this.chnl_gens[i] = new();
        this.env.chnl_agts[i].driver.req_mb = this.chnl_gens[i].req_mb;
        this.env.chnl_agts[i].driver.rsp_mb = this.chnl_gens[i].rsp_mb;
      end

      this.reg_gen = new();
      this.env.reg_agt.driver.req_mb = this.reg_gen.req_mb;
      this.env.reg_agt.driver.rsp_mb = this.reg_gen.rsp_mb;

      this.fmt_gen = new();
      this.env.fmt_agt.driver.req_mb = this.fmt_gen.req_mb;
      this.env.fmt_agt.driver.rsp_mb = this.fmt_gen.rsp_mb;

      rpt_pkg::logname = {this.name, "_check.log"};
      rpt_pkg::clean_log();
      $display("%s instantiated and connected objects", this.name);
    endfunction

    virtual task run();
      fork
        env.run();
      join_none
      rpt_pkg::rpt_msg("[TEST]",
        $sformatf("=====================%s AT TIME %0t STARTED=====================", this.name, $time),
        rpt_pkg::INFO,
        rpt_pkg::HIGH);
      this.do_reg();
      this.do_formatter();//先配置fmt的fifo
      this.do_data();
      rpt_pkg::rpt_msg("[TEST]",
        $sformatf("=====================%s AT TIME %0t FINISHED=====================", this.name, $time),
        rpt_pkg::INFO,
        rpt_pkg::HIGH);
      this.do_report();
      $finish();
    endtask

    // do register configuration
    virtual task do_reg();
    endtask

    // do external formatter down stream slave configuration
    virtual task do_formatter();
    endtask

    // do data transition from 3 channel slaves
    virtual task do_data();
    endtask

    // do simulation summary
    virtual function void do_report();
      this.env.do_report();
      rpt_pkg::do_report();
    endfunction

    virtual function void set_interface(virtual chnl_intf ch0_vif 
                                        ,virtual chnl_intf ch1_vif 
                                        ,virtual chnl_intf ch2_vif 
                                        ,virtual reg_intf reg_vif
                                        ,virtual fmt_intf fmt_vif
                                        ,virtual mcdf_intf mcdf_vif
                                      );
      this.env.chnl_agts[0].set_interface(ch0_vif);
      this.env.chnl_agts[1].set_interface(ch1_vif);
      this.env.chnl_agts[2].set_interface(ch2_vif);
      this.env.reg_agt.set_interface(reg_vif);
      this.env.fmt_agt.set_interface(fmt_vif);
      this.env.chker.set_interface(mcdf_vif);
    endfunction

    virtual function bit diff_value(int val1, int val2, string id = "value_compare");
      if(val1 != val2) begin
        rpt_pkg::rpt_msg("[CMPERR]", 
          $sformatf("ERROR! %s val1 %8x != val2 %8x", id, val1, val2), 
          rpt_pkg::ERROR, 
          rpt_pkg::TOP);
        return 0;
      end
      else begin
        rpt_pkg::rpt_msg("[CMPSUC]", 
          $sformatf("SUCCESS! %s val1 %8x == val2 %8x", id, val1, val2),
          rpt_pkg::INFO,
          rpt_pkg::HIGH);
        return 1;
      end
    endfunction

    virtual task idle_reg();
      void'(reg_gen.randomize() with {cmd == `IDLE; addr == 0; data == 0;});
      reg_gen.start();
    endtask

    virtual task write_reg(bit[7:0] addr, bit[31:0] data);
      void'(reg_gen.randomize() with {cmd == `WRITE; addr == local::addr; data == local::data;});
      reg_gen.start();
    endtask

    virtual task read_reg(bit[7:0] addr, output bit[31:0] data);
      void'(reg_gen.randomize() with {cmd == `READ; addr == local::addr;});
      reg_gen.start();
      data = reg_gen.data;
    endtask
  endclass

3.5 子类test

3.51 完整性测试

  class mcdf_data_consistence_basic_test extends mcdf_base_test;
    function new(string name = "mcdf_data_consistence_basic_test");
      super.new(name);
    endfunction

    task do_reg();
      bit[31:0] wr_val, rd_val;
      //寄存器规定了第三位为1、2、3时对应8、16、32。
      // slv0 with len=8,  prio=0, en=1
      wr_val = (1<<3)+(0<<1)+1;
      this.write_reg(`SLV0_RW_ADDR, wr_val);	//	把值写进去
      this.read_reg(`SLV0_RW_ADDR, rd_val);//再把写进去的值读回来
      void'(this.diff_value(wr_val, rd_val, "SLV0_WR_REG"));//作比较

      // slv1 with len=16, prio=1, en=1
      wr_val = (2<<3)+(1<<1)+1;
      this.write_reg(`SLV1_RW_ADDR, wr_val);
      this.read_reg(`SLV1_RW_ADDR, rd_val);
      void'(this.diff_value(wr_val, rd_val, "SLV1_WR_REG"));

      // slv2 with len=32, prio=2, en=1
      wr_val = (3<<3)+(2<<1)+1;
      this.write_reg(`SLV2_RW_ADDR, wr_val);
      this.read_reg(`SLV2_RW_ADDR, rd_val);
      void'(this.diff_value(wr_val, rd_val, "SLV2_WR_REG"));

      // send IDLE command
      this.idle_reg();
    endtask

    task do_formatter();	//定义了fmt的fifo为LONG_FIFO， HIGH_WIDTH
      void'(fmt_gen.randomize() with {fifo == LONG_FIFO; bandwidth == HIGH_WIDTH;});
      fmt_gen.start();
    endtask

    task do_data();//发送数据
      void'(chnl_gens[0].randomize() with {ntrans==100; ch_id==0; data_nidles==0; pkt_nidles==1; data_size==8; });
      void'(chnl_gens[1].randomize() with {ntrans==100; ch_id==1; data_nidles==1; pkt_nidles==4; data_size==16;});
      void'(chnl_gens[2].randomize() with {ntrans==100; ch_id==2; data_nidles==2; pkt_nidles==8; data_size==32;});
      fork
        chnl_gens[0].start();
        chnl_gens[1].start();
        chnl_gens[2].start();
      join
      #10us; // wait until all data haven been transfered through MCDF
    endtask
  endclass

从仿真波形图可以看出，只是一开始的时候3个通道同时发送，但是过了某个时间之后，你会发现已经按通道0、1、2的顺序依次发送了。但是在class env fork join中规定的并行发送。这是为何呢？

 fork
   this.chnl_agts[0].run();
   this.chnl_agts[1].run();
   this.chnl_agts[2].run();

 join

• 三个chnl_agts同时向slave-fifo发送数据，而发送到通道0、1、2的data_size不一样，分别为8、16、32，这些数据暂时存在了FIFO0、FIFO1、FIFO2里。
• 由于在mcdf_data_consistence_basic_test
  里定义了优先级排序是0>1>2，所以当三个通道同时申请仲裁时，先通过0的，再通过1的，最后才是2。所以结果不是并行发送。
• 如果你在mcdf_data_consistence_basic_test 把优先级排序改成2>1>0，那么情况就反了。

3.52其他测试

测试主要从do_reg、do_fmt和do_data来测试不同配置的寄存器、不同的数据。

3.52 寄存器读写测试

把写进寄存器的配置读回来，然后比较一下看对不对。

class mcdf_reg_stability_test extends mcdf_base_test;
    function new(string name = "mcdf_data_consistence_basic_test");
      super.new(name);
    endfunction

    task do_reg();
      bit[7:0] chnl_rw_addrs[] = '{`SLV0_RW_ADDR, `SLV1_RW_ADDR, `SLV2_RW_ADDR};
      bit[7:0] chnl_ro_addrs[] = '{`SLV0_R_ADDR, `SLV1_R_ADDR, `SLV2_R_ADDR};
      int pwidth = `PAC_LEN_WIDTH + `PRIO_WIDTH + 1;
      bit[31:0] check_pattern[] = '{((1<<pwidth)-1), 0, ((1<<pwidth)-1)};
      bit[31:0] wr_val, rd_val;

      // RW register access and bits toggle
      foreach(chnl_rw_addrs[i]) begin
        foreach(check_pattern[i]) begin
          wr_val = check_pattern[i];
          this.write_reg(chnl_rw_addrs[i], wr_val);
          this.read_reg(chnl_rw_addrs[i], rd_val);
          void'(this.diff_value(wr_val, rd_val));
        end
      end

      // RO register read access
      foreach(chnl_ro_addrs[i]) begin
          this.read_reg(chnl_ro_addrs[i], rd_val);
      end

      // send IDLE command
      this.idle_reg();
    endtask
  endclass

check_pattern[]中的数就是要写进寄存器里的数，此处的do_reg先把数写进reg，再读回来看是否一致。

3.53 寄存器稳定性测试

寄存器的相关说明：
地址0x00 通道1控制寄存器 32bits 读写寄存器
bit(0)：通道使能信号。1为打开，0位关闭。复位值为1。 bit(2:1)：优先级。0为最高，3为最低。复位值为3。
bit(5:3)：数据包长度，解码对应表为，
0对应长度4，1对应长度8，2对应长度16，3对应长度32，其它数值（4-7）均暂时对应长度32。复位值为0。
bit(31:6)：保留位，无法写入。复位值为0。

class mcdf_reg_illegal_access_test extends mcdf_base_test;
  function new(string name = "mcdf_reg_illegal_access_test");
    super.new(name);
  endfunction

  task do_reg();
    bit[7:0] chnl_rw_addrs[] = '{`SLV0_RW_ADDR, `SLV1_RW_ADDR, `SLV2_RW_ADDR};
    bit[7:0] chnl_ro_addrs[] = '{`SLV0_R_ADDR, `SLV1_R_ADDR, `SLV2_R_ADDR};
    int pwidth = `PAC_LEN_WIDTH + `PRIO_WIDTH + 1;  //=6
    bit[31:0] check_pattern[] = '{32'h0000_FFC0, 32'hFFFF_0000};
    bit[31:0] wr_val, rd_val;

    // RW register write reserved field and check
    foreach(chnl_rw_addrs[i]) begin
      foreach(check_pattern[j]) begin
        wr_val = check_pattern[j];
        this.write_reg(chnl_rw_addrs[i], wr_val);
        this.read_reg(chnl_rw_addrs[i], rd_val);
        void'(this.diff_value(wr_val & ((1<<pwidth)-1), rd_val));//将期望值和读出来的值对比
      end                                                       
    end

    // RO register write reserved field and check (no care readable field
    // value)
    foreach(chnl_ro_addrs[i]) begin
        wr_val = 32'hFFFF_FF00;
        this.write_reg(chnl_ro_addrs[i], wr_val);
        this.read_reg(chnl_ro_addrs[i], rd_val);
        void'(this.diff_value(0 , rd_val & 32'hFFFFFF00));
    end

    // send IDLE command
    this.idle_reg();
  endtask
endclass

• 寄存器说明中指出了只能读取低六位的数据。1与任何数想‘与’都是那个数本身，只需要将低6位和1相‘与’即可。最后和读回来的数作比较。
• 代码最后测试了ro寄存器是不是真的只读。

pwidth = `PAC_LEN_WIDTH + `PRIO_WIDTH + 1 = 6。

(1<<pwidth)-1='b1000000-1='b0111111。

wr_val & ((1<<pwidth)-1)也就是wr_val &'b0111111，表示只取wr_val的低6位。
diff_value(wr_val & ((1<<pwidth)-1), rd_val)将期望值与读回来的值rd_val进行比较。

3.54 数据通道开关检查

数据通道关闭时，mcdf_checker不会收到输入/出端的检测数据，因此也没有数据比较的信息。使能信号en默认初始值位1，当把en改位0后数据通道关闭，测试数据停留在数据通道端口，无法写入。同时ready为低，表示不接收数据。

3.55 优先级测试

将不同数据通道配置为相同或者不同的优先级，在数据通道使能的情况下进行测试 如果优先级相同，那么arbiter应该采取轮询机制从各个通道接收数据；如果优先级不同，那么arbiter应该先接收高优先级通道的数据，同时，最终所有的数据都应该从MCDF发送出来。

task do_arbiter_priority_check();
      int id;
      forever begin
        @(posedge this.arb_vif.clk iff (this.arb_vif.rstn && this.arb_vif.mon_ck.f2a_id_req===1));
        id = this.get_slave_id_with_prio();           //id的优先级最高
        if(id >= 0) begin
          @(posedge this.arb_vif.clk);
          if(!(refmod.get_field_value(0,RW_PRIO) == refmod.get_field_value(1,RW_PRIO)
          && refmod.get_field_value(1,RW_PRIO) == refmod.get_field_value(2,RW_PRIO)))
            if(this.arb_vif.mon_ck.a2s_acks[id] !== 1)    //id的优先级最高，那么对应的a2s_acks应该为1，否则报错
              rpt_pkg::rpt_msg("[CHKERR]",
                $sformatf("ERROR! %0t arbiter received f2a_id_req===1 and channel[%0d] raising request with high priority, but is not granted by arbiter", $time, id),
                rpt_pkg::ERROR,                               
                rpt_pkg::TOP);
        end
      end
    endtask

通过get_field_value函数获取每个chnl的优先级，如果三个优先级都不一样，那么就不会执行轮询，按照原来优先级的高低依次执行。
如果三个优先级都一样，那么就采用轮询机制，不执行接下来信息打印部分，否则就一定会报错。因为id的优先级最高，那么对应的a2s_acks应该为1。而轮询机制并不是按照优先级来控制a2s_acks信号，所以会出现错误。

if(!(refmod.get_field_value(0,RW_PRIO) == refmod.get_field_value(1,RW_PRIO)
   && refmod.get_field_value(1,RW_PRIO) == refmod.get_field_value(2,RW_PRIO)))

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