http://www.eng.utah.edu/~nmcdonal/Tutorials/BCDTutorial/BCDConversion.html

Binary to BCD Conversion Algorithm

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Purpose:

Conversion of a binary number into separate binary numbers representing digits of the decimal number. (this example is for 8-bits, other sizes follow the same pattern)

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Algorithm:

1. If any column (100's, 10's, 1's, etc.) is 5 or greater, add 3 to that column.
2. Shift all #'s to the left 1 position.
3. If 8 shifts have been performed, it's done! Evaluate each column for the BCD values.
4. Go to step 1.

Psuedo-Code:

Algorithm In Action:

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BCD Conversion in Hardware:

Verilog:

Binary to BCD conversion verilog code (9-bit)
module bin_2_bcd(B,P);
input [8:0] B;
output [10:0] P;
reg [10:0] P;
reg [19:0] z;
integer i;

always @(B)
  begin
    for(i = 0; i <= 19; i = i+1)
     z[i] = 0;
    z[11:3] = B;
    for(i = 0; i <= 5; i = i+1)
    begin
      if(z[12:9] > 4)    
         z[12:9] = z[12:9] + 3;
      
      if(z[16:13] > 4)    
         z[16:13] = z[16:13] + 3;
            
      z[19:1] = z[18:0];
        end
    P = z[19:9];        
  end             
endmodule