16 Constrain addr in range. Collect coverage

Sep 26, 2017 | Constraint, Coverage

Use constraints to restrict an address and range to be within a memory.Use coverage to collect results.

//This is the first episode released in a while. The video is sped up, which hopefully is better for consumption (even if it results in a funny voice). The presentation is also less rehearsed than previous episodes, so shows some trial and error at the end.

//Choosing a random location and amount of data to transfer from a memory.

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module top; 
  parameter MEMORY_SIZE = 100;


  class class1;
    rand logic [($clog2(MEMORY_SIZE)-1):0] addr;
    rand logic [($clog2(MEMORY_SIZE)-1):0] xfer_num;
    rand logic [($clog2(MEMORY_SIZE)-1):0] burst_num;

    constraint c_addr_range      { addr>=0; addr<MEMORY_SIZE; }
    constraint c_xfer_num        { xfer_num >0; xfer_num <=MEMORY_SIZE; }
    constraint c_burst_num       { burst_num>0; burst_num<=MEMORY_SIZE; }
    constraint c_total_xfer_size { (xfer_num*burst_num)<=MEMORY_SIZE; }

//  constraint c_sub_100 { (addr+amount_to_transfer()-1)<=MEMORY_SIZE; }

    function int amount_to_transfer();
      return(xfer_num*burst_num); 
    endfunction                    

    covergroup my_covergroup;
    option.per_instance = 1;
        coverpoint addr;
    endgroup

    function new();
      my_covergroup=new;
    endfunction

    function void post_randomize();
     $display("*****  addr:%0d\t xfer_num:%0d\t burst_num:%0d.  coverage:%3.2f%%",addr,xfer_num,burst_num,my_covergroup.get_inst_coverage());

     as_all_in_range : assert ( (addr + (xfer_num*burst_num)-1) <= MEMORY_SIZE ) else begin
       $display("ERROR.  OUT OF RANGE.");
     end
   endfunction
 endclass


 class1 my_class1;

 initial begin
   my_class1=new();

   $display("Choose a start address, and an amount of data to transfer.  Indicate location in memory of size %0d locations.  (%0d bits are needed to address memory of size %0d locations.) ", MEMORY_SIZE, $clog2(MEMORY_SIZE), MEMORY_SIZE);

   repeat (20) begin
     void'(my_class1.randomize());
    my_class1.my_covergroup.sample();
   end
   $finish;
 end

endmodule