Multiple conditions inside if, for queue values

SystemVerilog
, ,
1

I am not sure why can I not check multiple conditions with “OR” operator as shown below?

class bus_seq;
  rand bit queue[$]; 

  constraint qsize {
    queue.size() == 3;
  }
  
endclass : bus_seq

module randm();

  bus_seq bs = new();

  initial begin
    repeat (10) begin
      if (!bs.randomize()) 
        $error("Randomization failed"); 
      $display("  --> randomized queue = %p \n", bs.queue);
      //if ((bs.queue != {1,1,0}) or (bs.queue != {1,0,0})) begin //dont work
      //if ((bs.queue != {1,1,0}) | (bs.queue != {1,0,0})) begin //dont work
      //if ((bs.queue != {1,1,0}) || (bs.queue != {1,0,0})) begin //dont work
      if (bs.queue != {1,1,0}) begin //only option work, which is single value if condition
        $display("  --> NOT equal randomized queue = %p \n", bs.queue);
      end
    end
  end

endmodule : randm

Thank you.

2

In reply to megamind:

What did you meant “don’t work”? What did you see?

According to your code, I don’t see any problem with logical operator (||) or bitwise operator (|). It should work. The “or” instruction is not valid in SV.

However, I’m confuse that you are using condition “||” or “|” in this case, the if condition always reaches for any value of bs.queue.

And please note:

  • You should specify the size of each queue element: {1’b1, 1’b1, 1’b0}
  • You should use static cast to avoid compilation error (in some simulators):

class bus_seq;
  rand bit queue[$]; 
 
  constraint qsize {
    queue.size() == 3;
  }
 
endclass : bus_seq
 
module randm();
 
  bus_seq bs = new();
 
  initial begin
    typedef bit bit_queue_t[$];
    repeat (10) begin
      if (!bs.randomize()) 
        $error("Randomization failed"); 
      $display("  --> randomized queue = %p \n", bs.queue);
      //if ((bs.queue != {1,1,0}) or (bs.queue != {1,0,0})) begin //dont work
      //if ((bs.queue != {1,1,0}) | (bs.queue != {1,0,0})) begin //dont work
      if ((bs.queue != bit_queue_t'({1'b1,1'b1,1'b0})) || (bs.queue != bit_queue_t({1'b1,1'b0,1'b0}))) begin //dont work
      //if (bs.queue != {1,1,0}) begin //only option work, which is single value if condition
        $display("  --> NOT equal randomized queue = %p \n", bs.queue);
      end
    end
  end
 
endmodule : randm