Subversion Repositories m1_core

/*

 * M1 Multiplier

 *

 * Simple RTL-level Multiplier with Alternating Bit Protocol (ABP) interface.

 */

// 32-bit * 32-bit Integer Multiplier (this version is not optimized and always takes 32 cycles)

module m1_mul(

    input        sys_reset_i,      // System Reset

    input        sys_clock_i,      // System Clock

    input[31:0]  a_i,              // Operand A

    input[31:0]  b_i,              // Operand B

    input        signed_i,         // If multiplication is signed

    output reg[63:0] product_o,    // Product of multiplication

    input        abp_req_i,        // ABP Request

    output reg   abp_ack_o         // ABP Acknowledgement

  );

  // Registers

  reg[63:0]    a_latched;        // Latched 'a' input

  reg[31:0]    b_latched;        // Latched 'b' input

  reg[63:0]    product_tmp;      // Temporary result

  reg          negative_output;  // If output is negative

  reg[5:0]     count;            // Downward counter (32->0)

  reg          abp_last;         // Level of last ABP request

  // Sequential logic

  always @(posedge sys_clock_i) begin

    // Initialization

    if(sys_reset_i) begin

      product_o = 0;

      abp_ack_o = 0;

      negative_output = 0;

      count = 6'd0;

      abp_last = 0;

    // New request

    end else if(abp_req_i!=abp_last) begin

      abp_last = abp_req_i;     // Latch level of ABP request

      count  = 6'd32;           // Start counter

      product_tmp = 0;          // Initialize result

      a_latched = (!signed_i || !a_i[31]) ? { 32'd0, a_i } : { 32'd0, (~a_i+1'b1) };

      b_latched = (!signed_i || !b_i[31]) ? b_i : (~b_i + 1'b1);

      negative_output = signed_i && (a_i[31] ^ b_i[31]);

      product_o = (!negative_output) ? product_tmp : (~product_tmp+1);  // Degugging only

    // Calculating

    end else if(count>0) begin

      count = count-1;

      if(b_latched[0]==1) product_tmp = product_tmp + a_latched;

      a_latched = a_latched << 1;

      b_latched = b_latched >> 1;

      product_o = (!negative_output) ? product_tmp : (~product_tmp + 1);  // Debugging only

    // Return the result

    end else if(count==0) begin

      abp_ack_o = abp_req_i;    // Return the result

      product_o = (!negative_output) ? product_tmp : (~product_tmp + 1);

    end

  end

endmodule