class spi_monitor;

  virtual sysreg_if	vif;
  virtual spi_if	wif;
  virtual sram_if	xif;

  //collect MOSI(din) & MISO(dout) 
  bit			din[$];
  bit[31:0]		dout[$];

  int			pktnum;
  int			pkt_i;


  function new();
  endfunction
  extern task write_monitor();
  extern task read_monitor();
  extern task do_mon();

endclass : spi_monitor 


task spi_monitor::do_mon();

  fork

    while(1) begin
      if(pkt_i==pktnum) break;
      write_monitor();
    end

    while(1) begin
      if(pkt_i==pktnum) break;
      read_monitor();
    end

    repeat(pktnum) begin: kill_progress
      @(negedge wif.csn);
      pkt_i++;
    end  

  join

endtask: do_mon


//monitor1: write_monitor(mosi)
task spi_monitor::write_monitor();
    bit		write_temp[$];

	@(negedge wif.csn);
	while(1) begin
	  //Sample miso data @(posedge sclk) as DUT does.
	  @(posedge wif.sclk or posedge wif.csn);
	  if(wif.error_check | wif.csn)
	    break;
	  write_temp.push_back(wif.mosi);
	end
	//Keep the write-cycle data until anothor one occurs
        if(write_temp[0]==1'b0)
	  din = write_temp;
	din[0] = write_temp[0];
	write_temp.delete();

endtask:  write_monitor

//monitor2: read_monitor(miso)
task spi_monitor::read_monitor();
    bit[31:0]	read_temp;
    int		size;
    int		i=0;

 
	@(negedge wif.csn);
	
	for(i=0;i<32;i++) begin
	  @(posedge wif.sclk or posedge wif.csn)
	  if(wif.error_check | wif.csn) 
	    break;
	  read_temp[i] = wif.mosi;
	end
  	size = read_temp[0] ? (read_temp[1] ? 16 : 1) : 0; 

	read_temp = 32'b0;
	dout.delete();
  	repeat(size) begin
    	  //One 32bit-word is sampled everytime a for-circulation runs
    	  for(i=0;i<32;i++) begin
            //Sample miso data @(negedge sclk) for stability.
            @(negedge wif.sclk or posedge wif.csn);
            if(wif.csn)
	      break;
	    read_temp[31-i] = wif.miso;
          end  
          if(!wif.csn) begin
            dout.push_back(read_temp);
            $display("miso:\t\t%b\t\t    **",read_temp);
          end
        end
	if(!wif.csn) @(posedge wif.csn);

endtask:  read_monitor