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`timescale 1ns / 1ps

// ============================================================================

//        __

//   \\__/ o\    (C) 2012-2022  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch@finitron.ca

//       ||

//

//      BCDMath.sv

//

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// modification, are permitted provided that the following conditions are met:

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// 1. Redistributions of source code must retain the above copyright notice, this

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//

// ============================================================================

//

// Could use the following approach for add/sub but it ends up being larger

// than using an adjustment lookup table.

module BCDAddNyb(ci,a,b,o,c);

input ci;               // carry input

input [3:0] a;

input [3:0] b;

output [3:0] o;

output c;

wire c0;

reg [4:0] hsN0;

always  @*

begin

        hsN0 = a[3:0] + b[3:0] + ci;

        if (hsN0 > 5'd9)

                hsN0 = hsN0 + 3'd6;

end

assign o = hsN0[3:0];

assign c = hsN0[4];

endmodule

module BCDAdd(ci,a,b,o,c);

input ci;               // carry input

input [7:0] a;

input [7:0] b;

output [7:0] o;

output c;

wire c0,c1;

wire [4:0] hsN0 = a[3:0] + b[3:0] + ci;

wire [4:0] hsN1 = a[7:4] + b[7:4] + c0;

BCDAddAdjust u1 (hsN0,o[3:0],c0);

BCDAddAdjust u2 (hsN1,o[7:4],c);

endmodule

module BCDAdd4(ci,a,b,o,c,c8);

input ci;               // carry input

input [15:0] a;

input [15:0] b;

output [15:0] o;

output c;

output c8;

wire c0,c1,c2;

assign c8 = c1;

wire [4:0] hsN0 = a[3:0] + b[3:0] + ci;

wire [4:0] hsN1 = a[7:4] + b[7:4] + c0;

wire [4:0] hsN2 = a[11:8] + b[11:8] + c1;

wire [4:0] hsN3 = a[15:12] + b[15:12] + c2;

BCDAddAdjust u1 (hsN0,o[3:0],c0);

BCDAddAdjust u2 (hsN1,o[7:4],c1);

BCDAddAdjust u3 (hsN2,o[11:8],c2);

BCDAddAdjust u4 (hsN3,o[15:12],c);

endmodule

/*

module BCDAddN(ci,a,b,o,co);

parameter N=24;

input ci;               // carry input

input [N*4-1:0] a;

input [N*4-1:0] b;

output [N*4-1:0] o;

output co;

genvar g;

generate begin : gBCDAddN

reg [4:0] hsN [0:N-1];

wire [N:0] c;

assign c[0] = ci;

assign co = c[N];

for (g = 0; g < N; g = g + 1)

        always @*

                hsN[g] = a[g*4+3:g*4] + b[g*4+3:g*4] + c[g];

for (g = 0; g < N; g = g + 1)

        BCDAddAdjust u1 (hsN[g],o[g*4+3:g*4],c[g+1]);

end

endgenerate

endmodule

*/

/*

module BCDAddN(ci,a,b,o,co);

parameter N=34; // Number of digits

input ci;                               // carry input

input [N*4-1:0] a;

input [N*4-1:0] b;

output reg [N*4-1:0] o;

output reg co;

reg [N*4-1:0] sum1;

reg [N-1:0] c;  // inter-digit carries

reg [3:0] s1 [0:N-1];   // the digits of sum1 (just wires)

reg [4:0] s2 [0:N-1];   // the digits of sum2

reg [3:0] sixes [0:N-1];        // 0x666...

reg [3:0] ag [0:N-1];   // the digits of a

reg [3:0] bg [0:N-1];   // the digits of b

always_comb

        sum1 = a + b + ci;

always_comb

        c[0] = 1'b0;

genvar dig;

generate begin : gBCDAdd

for (dig = 0; dig < N; dig = dig + 1)

begin

        always_comb

                s1[dig] = sum1[dig*4+3:dig*4];  // these are just wires

        always_comb

                ag[dig] = a[dig*4+3:dig*4];                     // just wires

        always_comb

                bg[dig] = b[dig*4+3:dig*4];                     // just wires

        always_comb

                if (dig==0)

                        sixes[dig] = 4'd6 | ci;                         // except for first digt, the constant 6

                else

                        sixes[dig] = 4'd6;

        always_comb

                if (dig==0)

                        s2[dig] = ag[dig] + bg[dig] + sixes[dig];

                else

                        s2[dig] = ag[dig] + bg[dig] + (sixes[dig]|s2[dig-1][4]);

        always_comb                                                                                             // capture inter-digit carries

                c[dig] = s2[dig][4];

        always_comb                                                                                             // select based on digit value

                o[dig*4+3:dig*4] = (s1[dig] > 4'd9) ? s2[dig] : s1[dig];

end

always_comb

        co = c[N-1];

end

endgenerate

endmodule

*/

/* Does not work yet.

module BCDAddN(ci,a,b,o,co);

parameter N=34;

input ci;               // carry input

input [N*4-1:0] a;

input [N*4-1:0] b;

output reg [N*4-1:0] o;

output reg co;

reg [N*4:0] sum1, sum2, sum3, c;

reg [N*4-1:0] sixes;

always_comb

        sum1 = a + b;

always_comb

        sum2 = sum1 + {c,4'd0};

always_comb

        {co,o} = {c[N*4],sum3};

genvar g;

generate begin : gSixes

for (g = 0; g < N; g = g + 1)

begin

        always_comb

                c[g*4+3:g*4] = {3'b0,sum1[g*4+3:g*4] > 4'd9};

        always_comb

                if (g==0)

                        sixes[g*4+3:g*4] = (c[g*4] ? 4'd6 : 4'd0) | ci;

                else

                        sixes[g*4+3:g*4] = c[g*4] ? 4'd6 : 4'd0;

        always_comb

                if (g==N-1)

                        sum3[g*4+4:g*4] = sum2[g*4+3:g*4] + sixes[g*4+3:g*4];

                else

                        sum3[g*4+3:g*4] = sum2[g*4+3:g*4] + sixes[g*4+3:g*4];

end

always_comb

        c[N*4] = 1'b0;

end

endgenerate

endmodule

*/

module BCDSub(ci,a,b,o,c);

input ci;               // carry input

input [7:0] a;

input [7:0] b;

output [7:0] o;

output c;

wire c0,c1;

wire [4:0] hdN0 = a[3:0] - b[3:0] - ci;

wire [4:0] hdN1 = a[7:4] - b[7:4] - c0;

BCDSubAdjust u1 (hdN0,o[3:0],c0);

BCDSubAdjust u2 (hdN1,o[7:4],c);

endmodule

module BCDSub4(ci,a,b,o,c,c8);

input ci;               // carry input

input [15:0] a;

input [15:0] b;

output [15:0] o;

output c;

output c8;

wire c0,c1,c2;

assign c8 = c1;

wire [4:0] hdN0 = a[3:0] - b[3:0] - ci;

wire [4:0] hdN1 = a[7:4] - b[7:4] - c0;

wire [4:0] hdN2 = a[11:8] - b[11:8] - c1;

wire [4:0] hdN3 = a[15:12] - b[15:12] - c2;

BCDSubAdjust u1 (hdN0,o[3:0],c0);

BCDSubAdjust u2 (hdN1,o[7:4],c1);

BCDSubAdjust u3 (hdN2,o[11:8],c2);

BCDSubAdjust u4 (hdN3,o[15:12],c);

endmodule

/*

module BCDSubN(ci,a,b,o,co);

parameter N=34;

input ci;               // carry input

input [N*4-1:0] a;

input [N*4-1:0] b;

output reg [N*4-1:0] o;

output reg co;

reg [N*4:0] sum1, sum2, sum3, c;

reg [N*4-1:0] sixes;

always_comb

        sum1 = a - b;

always_comb

        sum2 = sum1 - {c,4'd0};

always_comb

        {co,o} = {c[N*4],sum3};

genvar g;

generate begin : gSixes

for (g = 0; g < N; g = g + 1)

begin

        always_comb

                c[g*4+3:g*4] = {3'b0,sum1[g*4+3:g*4] > 4'd9};

        always_comb

                if (g==0)

                        sixes[g*4+3:g*4] = (c[g*4] ? 4'd6 : 4'd0) | ci;

                else

                        sixes[g*4+3:g*4] = c[g*4] ? 4'd6 : 4'd0;

        always_comb

                sum3[g*4+3:g*4] = sum2[g*4+3:g*4] - sixes[g*4+3:g*4];

end

end

endgenerate

always_comb

        c[N*4] = 1'b0;

endmodule

*/

module BCDSubN(ci,a,b,o,co);

parameter N=24;

input ci;               // carry input

input [N*4-1:0] a;

input [N*4-1:0] b;

output [N*4-1:0] o;

output co;

genvar g;

generate begin : gBCDSubN

reg [4:0] hdN [0:N-1];

wire [N:0] c;

assign c[0] = ci;

assign co = c[N];

for (g = 0; g < N; g = g + 1)

        always @*

                hdN[g] = a[g*4+3:g*4] - b[g*4+3:g*4] - c[g];

for (g = 0; g < N; g = g + 1)

        BCDSubAdjust u1 (hdN[g],o[g*4+3:g*4],c[g+1]);

end

endgenerate

endmodule

module BCDAddAdjust(i,o,c);

input [4:0] i;

output [3:0] o;

reg [3:0] o;

output c;

reg c;

always @(i)

case(i)

5'h0: begin o = 4'h0; c = 1'b0; end

5'h1: begin o = 4'h1; c = 1'b0; end

5'h2: begin o = 4'h2; c = 1'b0; end

5'h3: begin o = 4'h3; c = 1'b0; end

5'h4: begin o = 4'h4; c = 1'b0; end

5'h5: begin o = 4'h5; c = 1'b0; end

5'h6: begin o = 4'h6; c = 1'b0; end

5'h7: begin o = 4'h7; c = 1'b0; end

5'h8: begin o = 4'h8; c = 1'b0; end

5'h9: begin o = 4'h9; c = 1'b0; end

5'hA: begin o = 4'h0; c = 1'b1; end

5'hB: begin o = 4'h1; c = 1'b1; end

5'hC: begin o = 4'h2; c = 1'b1; end

5'hD: begin o = 4'h3; c = 1'b1; end

5'hE: begin o = 4'h4; c = 1'b1; end

5'hF: begin o = 4'h5; c = 1'b1; end

5'h10:  begin o = 4'h6; c = 1'b1; end

5'h11:  begin o = 4'h7; c = 1'b1; end

5'h12:  begin o = 4'h8; c = 1'b1; end

5'h13:  begin o = 4'h9; c = 1'b1; end

default:        begin o = 4'h9; c = 1'b1; end

endcase

endmodule

module BCDSubAdjust(i,o,c);

input [4:0] i;

output [3:0] o;

reg [3:0] o;

output c;

reg c;

always @(i)

case(i)

5'h0: begin o = 4'h0; c = 1'b0; end

5'h1: begin o = 4'h1; c = 1'b0; end

5'h2: begin o = 4'h2; c = 1'b0; end

5'h3: begin o = 4'h3; c = 1'b0; end

5'h4: begin o = 4'h4; c = 1'b0; end

5'h5: begin o = 4'h5; c = 1'b0; end

5'h6: begin o = 4'h6; c = 1'b0; end

5'h7: begin o = 4'h7; c = 1'b0; end

5'h8: begin o = 4'h8; c = 1'b0; end

5'h9: begin o = 4'h9; c = 1'b0; end

5'h16: begin o = 4'h0; c = 1'b1; end

5'h17: begin o = 4'h1; c = 1'b1; end

5'h18: begin o = 4'h2; c = 1'b1; end

5'h19: begin o = 4'h3; c = 1'b1; end

5'h1A: begin o = 4'h4; c = 1'b1; end

5'h1B: begin o = 4'h5; c = 1'b1; end

5'h1C: begin o = 4'h6; c = 1'b1; end

5'h1D: begin o = 4'h7; c = 1'b1; end

5'h1E: begin o = 4'h8; c = 1'b1; end

5'h1F: begin o = 4'h9; c = 1'b1; end

default: begin o = 4'h9; c = 1'b1; end

endcase

endmodule

// Multiply two BCD digits

// Method used is table lookup

module BCDMul1(a,b,o);

input [3:0] a;

input [3:0] b;

output [7:0] o;

reg [7:0] o;

always @(a or b)

casex({a,b})

8'h00: o = 8'h00;

8'h01: o = 8'h00;

8'h02: o = 8'h00;

8'h03: o = 8'h00;

8'h04: o = 8'h00;

8'h05: o = 8'h00;

8'h06: o = 8'h00;

8'h07: o = 8'h00;

8'h08: o = 8'h00;

8'h09: o = 8'h00;

8'h10: o = 8'h00;

8'h11: o = 8'h01;

8'h12: o = 8'h02;

8'h13: o = 8'h03;

8'h14: o = 8'h04;

8'h15: o = 8'h05;

8'h16: o = 8'h06;

8'h17: o = 8'h07;

8'h18: o = 8'h08;

8'h19: o = 8'h09;

8'h20: o = 8'h00;

8'h21: o = 8'h02;

8'h22: o = 8'h04;

8'h23: o = 8'h06;

8'h24: o = 8'h08;

8'h25: o = 8'h10;

8'h26: o = 8'h12;

8'h27: o = 8'h14;

8'h28: o = 8'h16;

8'h29: o = 8'h18;

8'h30: o = 8'h00;

8'h31: o = 8'h03;

8'h32: o = 8'h06;

8'h33: o = 8'h09;

8'h34: o = 8'h12;

8'h35: o = 8'h15;

8'h36: o = 8'h18;

8'h37: o = 8'h21;

8'h38: o = 8'h24;

8'h39: o = 8'h27;

8'h40: o = 8'h00;

8'h41: o = 8'h04;

8'h42: o = 8'h08;

8'h43: o = 8'h12;

8'h44: o = 8'h16;

8'h45: o = 8'h20;

8'h46: o = 8'h24;

8'h47: o = 8'h28;

8'h48: o = 8'h32;

8'h49: o = 8'h36;

8'h50: o = 8'h00;

8'h51: o = 8'h05;

8'h52: o = 8'h10;

8'h53: o = 8'h15;

8'h54: o = 8'h20;

8'h55: o = 8'h25;

8'h56: o = 8'h30;

8'h57: o = 8'h35;

8'h58: o = 8'h40;

8'h59: o = 8'h45;

8'h60: o = 8'h00;

8'h61: o = 8'h06;

8'h62: o = 8'h12;

8'h63: o = 8'h18;

8'h64: o = 8'h24;

8'h65: o = 8'h30;

8'h66: o = 8'h36;

8'h67: o = 8'h42;

8'h68: o = 8'h48;

8'h69: o = 8'h54;

8'h70: o = 8'h00;

8'h71: o = 8'h07;

8'h72: o = 8'h14;

8'h73: o = 8'h21;

8'h74: o = 8'h28;

8'h75: o = 8'h35;

8'h76: o = 8'h42;

8'h77: o = 8'h49;

8'h78: o = 8'h56;

8'h79: o = 8'h63;

8'h80: o = 8'h00;

8'h81: o = 8'h08;

8'h82: o = 8'h16;

8'h83: o = 8'h24;

8'h84: o = 8'h32;

8'h85: o = 8'h40;

8'h86: o = 8'h48;

8'h87: o = 8'h56;

8'h88: o = 8'h64;

8'h89: o = 8'h72;

8'h90: o = 8'h00;

8'h91: o = 8'h09;

8'h92: o = 8'h18;

8'h93: o = 8'h27;

8'h94: o = 8'h36;

8'h95: o = 8'h45;

8'h96: o = 8'h54;

8'h97: o = 8'h63;

8'h98: o = 8'h72;

8'h99: o = 8'h81;

default:        o = 8'h00;

endcase

endmodule

// Multiply two pairs of BCD digits

// handles from 0x0 to 99x99

module BCDMul2(a,b,o);

input [7:0] a;

input [7:0] b;

output [15:0] o;

wire [7:0] p1,p2,p3,p4;

wire [15:0] s1;

BCDMul1 u1 (a[3:0],b[3:0],p1);

BCDMul1 u2 (a[7:4],b[3:0],p2);

BCDMul1 u3 (a[3:0],b[7:4],p3);

BCDMul1 u4 (a[7:4],b[7:4],p4);

BCDAdd4 u5 (1'b0,{p4,p1},{4'h0,p2,4'h0},s1);

BCDAdd4 u6 (1'b0,s1,{4'h0,p3,4'h0},o);

endmodule

module BCDMul4(a,b,o);

input [15:0] a;

input [15:0] b;

output [31:0] o;

wire [15:0] p1,p2,p3,p4;

wire [31:0] s1;

BCDMul2 u1 (a[7:0],b[7:0],p1);

BCDMul2 u2 (a[15:8],b[7:0],p2);

BCDMul2 u3 (a[7:0],b[15:8],p3);

BCDMul2 u4 (a[15:8],b[15:8],p4);

BCDAddN #(.N(8)) u5 (1'b0,{p4,p1},{8'h0,p2,8'h0},s1);

BCDAddN #(.N(8)) u6 (1'b0,s1,{8'h0,p3,8'h0},o);

endmodule

module BCDMul8(a,b,o);

input [31:0] a;

input [31:0] b;

output [63:0] o;

wire [31:0] p1,p2,p3,p4;

wire [63:0] s1;

BCDMul4 u1 (a[15:0],b[15:0],p1);

BCDMul4 u2 (a[31:16],b[15:0],p2);

BCDMul4 u3 (a[15:0],b[31:16],p3);

BCDMul4 u4 (a[31:16],b[31:16],p4);

BCDAddN #(.N(16)) u5 (1'b0,{p4,p1},{16'h0,p2,16'h0},s1);

BCDAddN #(.N(16)) u6 (1'b0,s1,{16'h0,p3,16'h0},o);

endmodule

module BCDMul16(a,b,o);

input [63:0] a;

input [63:0] b;

output [127:0] o;

wire [63:0] p1,p2,p3,p4;

wire [127:0] s1;

BCDMul8 u1 (a[31:0],b[31:0],p1);

BCDMul8 u2 (a[63:32],b[31:0],p2);

BCDMul8 u3 (a[31:0],b[63:32],p3);

BCDMul8 u4 (a[63:32],b[63:32],p4);

BCDAddN #(.N(32)) u5 (1'b0,{p4,p1},{32'h0,p2,32'h0},s1);

BCDAddN #(.N(32)) u6 (1'b0,s1,{32'h0,p3,32'h0},o);

endmodule

module BCDMul32(a,b,o);

input [127:0] a;

input [127:0] b;

output [255:0] o;

wire [127:0] p1,p2,p3,p4;

wire [255:0] s1;

BCDMul16 u1 (a[63:0],b[63:0],p1);

BCDMul16 u2 (a[127:64],b[63:0],p2);

BCDMul16 u3 (a[63:0],b[127:64],p3);

BCDMul16 u4 (a[127:64],b[127:64],p4);

BCDAddN #(.N(64)) u5 (1'b0,{p4,p1},{64'h0,p2,64'h0},s1);

BCDAddN #(.N(64)) u6 (1'b0,s1,{64'h0,p3,64'h0},o);

endmodule

module BCDMul_tb();

wire [15:0] o1,o2,o3,o4;

BCDMul2 u1 (8'h00,8'h00,o1);

BCDMul2 u2 (8'h99,8'h99,o2);

BCDMul2 u3 (8'h25,8'h18,o3);

BCDMul2 u4 (8'h37,8'h21,o4);

endmodule

module BinToBCD(i, o);

input [7:0] i;

output [11:0] o;

reg [11:0] tbl [0:255];

genvar g;

generate begin : gTbl

reg [3:0] n0 [0:255];

reg [3:0] n1 [0:255];

reg [3:0] n2 [0:255];

for (g = 0; g < 256; g = g + 1) begin

        initial begin

                n0[g] = g % 10;

                n1[g] = g / 10;

                n2[g] = g / 100;

                tbl[g] <= {n2[g],n1[g],n0[g]};

        end

end

assign o = tbl[i];

end

endgenerate

endmodule

// Perform a logical shift to the right.

module BCDSRL(ci, i, o, co);

parameter N=4;

input ci;

input [N*4-1:0] i;

output reg [N*4-1:0] o;

output co;

reg [N:0] c;

genvar g;

generate begin

always_comb

        c[N] = ci;

for (g = N - 1; g >= 0; g = g - 1)

always_comb

        c[g] = i[g*4];

for (g = N - 1; g >= 0; g = g - 1)

always_comb

begin

        o[g*4+3:g*4] = {1'b0,i[g*4+3:g*4+1]};

        // Because there is a divide by two, the value will range between 0 and 4.

        // Adding 5 keeps it within deicmal boundaries of 0 to 9. No carry can be

        // generated

        if (c[N+1])

                o[g*4+3:g*4] = o[g*4+3:g*4] + 4'd5;

end

        assign co = c[0];

end

endgenerate

endmodule