Question

Can you explain the hardware (using xor gates) implementation of the circuit that calculate CRC key, suppose the polynomial key is x^4 + x^2 +x+1 and the message 100110011010.

I need the hardware implementation only.

Answer 1

This gives the following CRC polynomial (press RETURN to update):

P(x) = x11+ x8+ x7+ x4+ x3+ x1

module CRC_Unit(BITVAL, BITSTRB, CLEAR, CRC);

   input        BITVAL;                            // Next input bit

   input        BITSTRB;                           // Current bit valid (Clock)

   input        CLEAR;                             // Init CRC value

   output [10:0] CRC;                               // Current output CRC value

   reg    [10:0] CRC;                               // We need output registers

   wire         inv;

  

   assign inv = BITVAL ^ CRC[10];                   // XOR required?

  

   always @(posedge BITSTRB or posedge CLEAR) begin

      if (CLEAR) begin

         CRC = 0;                                  // Init before calculation

         end

      else begin

         CRC[10] = CRC[9];

         CRC[9] = CRC[8];

         CRC[8] = CRC[7] ^ inv;

         CRC[7] = CRC[6] ^ inv;

         CRC[6] = CRC[5];

         CRC[5] = CRC[4];

         CRC[4] = CRC[3] ^ inv;

         CRC[3] = CRC[2] ^ inv;

         CRC[2] = CRC[1];

         CRC[1] = CRC[0] ^ inv;

         CRC[0] = inv;

         end

      end

  

endmodule