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[/] [versatile_library/] [trunk/] [rtl/] [verilog/] [arith.v] - Rev 35

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//////////////////////////////////////////////////////////////////////
////                                                              ////
////  Arithmetic functions                                        ////
////                                                              ////
////  Description                                                 ////
////  Arithmetic functions for ALU and DSP                        ////
////                                                              ////
////                                                              ////
////  To Do:                                                      ////
////   -                                                          ////
////                                                              ////
////  Author(s):                                                  ////
////      - Michael Unneback, unneback@opencores.org              ////
////        ORSoC AB                                              ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2010 Authors and OPENCORES.ORG                 ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file is free software; you can redistribute it   ////
//// and/or modify it under the terms of the GNU Lesser General   ////
//// Public License as published by the Free Software Foundation; ////
//// either version 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source is distributed in the hope that it will be       ////
//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////
//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////
//// PURPOSE.  See the GNU Lesser General Public License for more ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
 
// signed multiplication
module vl_mults (a,b,p);
parameter operand_a_width = 18;
parameter operand_b_width = 18;
parameter result_hi = 35;
parameter result_lo = 0;
input [operand_a_width-1:0] a;
input [operand_b_width-1:0] b;
output [result_hi:result_lo] p;
wire signed [operand_a_width-1:0] ai;
wire signed [operand_b_width-1:0] bi;
wire signed [operand_a_width+operand_b_width-1:0] result;
 
    assign ai = a;
    assign bi = b;
    assign result = ai * bi;
    assign p = result[result_hi:result_lo];
 
endmodule
 
module vl_mults18x18 (a,b,p);
input [17:0] a,b;
output [35:0] p;
vl_mult
    # (.operand_a_width(18), .operand_b_width(18))
    mult0 (.a(a), .b(b), .p(p));
endmodule
 
// unsigned multiplication
module vl_mult (a,b,p);
parameter operand_a_width = 18;
parameter operand_b_width = 18;
parameter result_hi = 35;
parameter result_lo = 0;
input [operand_a_width-1:0] a;
input [operand_b_width-1:0] b;
output [result_hi:result_hi] p;
 
wire [operand_a_width+operand_b_width-1:0] result;
 
    assign result = a * b;
    assign p = result[result_hi:result_lo];
 
endmodule
 
// shift unit
// supporting the following shift functions
//   SLL
//   SRL
//   SRA
`define SHIFT_UNIT_MULT # ( .operand_a_width(25), .operand_b_width(16), .result_hi(14), .result_lo(7))
module vl_shift_unit_32( din, s, dout, opcode);
input [31:0] din; // data in operand
input [4:0] s; // shift operand
input [1:0] opcode;
output [31:0] dout;
 
parameter opcode_sll = 2'b00;
//parameter opcode_srl = 2'b01;
parameter opcode_sra = 2'b10;
//parameter opcode_ror = 2'b11;
 
wire sll, sra;
assign sll = opcode == opcode_sll;
assign sra = opcode == opcode_sra;
 
wire [15:1] s1;
wire [3:0] sign;
wire [7:0] tmp [0:3];
 
// first stage is multiplier based
// shift operand as fractional 8.7
assign s1[15] = sll & s[2:0]==3'd7;
assign s1[14] = sll & s[2:0]==3'd6;
assign s1[13] = sll & s[2:0]==3'd5;
assign s1[12] = sll & s[2:0]==3'd4;
assign s1[11] = sll & s[2:0]==3'd3;
assign s1[10] = sll & s[2:0]==3'd2;
assign s1[ 9] = sll & s[2:0]==3'd1;
assign s1[ 8] = s[2:0]==3'd0;
assign s1[ 7] = !sll & s[2:0]==3'd1;
assign s1[ 6] = !sll & s[2:0]==3'd2;
assign s1[ 5] = !sll & s[2:0]==3'd3;
assign s1[ 4] = !sll & s[2:0]==3'd4;
assign s1[ 3] = !sll & s[2:0]==3'd5;
assign s1[ 2] = !sll & s[2:0]==3'd6;
assign s1[ 1] = !sll & s[2:0]==3'd7;
 
assign sign[3] = din[31] & sra;
assign sign[2] = sign[3] & (&din[31:24]);
assign sign[1] = sign[2] & (&din[23:16]);
assign sign[0] = sign[1] & (&din[15:8]);
vl_mults `SHIFT_UNIT_MULT mult_byte3 ( .a({sign[3], {8{sign[3]}},din[31:24], din[23:16]}), .b({1'b0,s1}), .p(tmp[3]));
vl_mults `SHIFT_UNIT_MULT mult_byte2 ( .a({sign[2], din[31:24]  ,din[23:16],  din[15:8]}), .b({1'b0,s1}), .p(tmp[2]));
vl_mults `SHIFT_UNIT_MULT mult_byte1 ( .a({sign[1], din[23:16]  ,din[15:8],   din[7:0]}), .b({1'b0,s1}), .p(tmp[1]));
vl_mults `SHIFT_UNIT_MULT mult_byte0 ( .a({sign[0], din[15:8]   ,din[7:0],    8'h00}),      .b({1'b0,s1}), .p(tmp[0]));
 
// second stage is multiplexer based
// shift on byte level
 
// mux byte 3
assign dout[31:24] = (s[4:3]==2'b00) ? tmp[3] :
                     (sll & s[4:3]==2'b01) ? tmp[2] :
                     (sll & s[4:3]==2'b10) ? tmp[1] :
                     (sll & s[4:3]==2'b11) ? tmp[0] :
                     {8{sign[3]}};
 
// mux byte 2
assign dout[23:16] = (s[4:3]==2'b00) ? tmp[2] :
                     (sll & s[4:3]==2'b01) ? tmp[1] :
                     (sll & s[4:3]==2'b10) ? tmp[0] :
                     (sll & s[4:3]==2'b11) ? {8{1'b0}} :
                     (s[4:3]==2'b01) ? tmp[3] :
                     {8{sign[3]}};
 
// mux byte 1
assign dout[15:8]  = (s[4:3]==2'b00) ? tmp[1] :
                     (sll & s[4:3]==2'b01) ? tmp[0] :
                     (sll & s[4:3]==2'b10) ? {8{1'b0}} :
                     (sll & s[4:3]==2'b11) ? {8{1'b0}} :
                     (s[4:3]==2'b01) ? tmp[2] :
                     (s[4:3]==2'b10) ? tmp[3] :
                     {8{sign[3]}};
 
// mux byte 0
assign dout[7:0]   = (s[4:3]==2'b00) ? tmp[0] :
                     (sll) ?  {8{1'b0}}:
                     (s[4:3]==2'b01) ? tmp[1] :
                     (s[4:3]==2'b10) ? tmp[2] :
                     tmp[3];
 
endmodule
 
// logic unit
// supporting the following logic functions
//    a and b
//    a or  b
//    a xor b
//    not b
module vl_logic_unit( a, b, result, opcode);
parameter width = 32;
parameter opcode_and = 2'b00;
parameter opcode_or  = 2'b01;
parameter opcode_xor = 2'b10;
input [width-1:0] a,b;
output [width-1:0] result;
input [1:0] opcode;
 
assign result = (opcode==opcode_and) ? a & b :
                (opcode==opcode_or)  ? a | b :
                (opcode==opcode_xor) ? a ^ b :
                b;
 
endmodule
 
module vl_arith_unit ( a, b, c_in, add_sub, sign, result, c_out, z, ovfl);
parameter width = 32;
parameter opcode_add = 1'b0;
parameter opcode_sub = 1'b1;
input [width-1:0] a,b;
input c_in, add_sub, sign;
output [width-1:0] result;
output c_out, z, ovfl;
 
assign {c_out,result} = {(a[width-1] & sign),a} + ({a[width-1] & sign,b} ^ {(width+1){(add_sub==opcode_sub)}}) + {{(width-1){1'b0}},(c_in | (add_sub==opcode_sub))};
assign z = (result=={width{1'b0}});
assign ovfl = ( a[width-1] &  b[width-1] & ~result[width-1]) |
               (~a[width-1] & ~b[width-1] &  result[width-1]);
endmodule
 

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