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//------------------------------
// Module name: bin2bcd_8
// Function: Converts an 8-bit binary number to 3 digits BCD
// .... it uses a shift-and-add3 algorithm
// Creator: Peter Cheung
// Version: 1.0
// Date: 17 Sept 2016
//------------------------------
// For more explanation of how this work, see
// ... instructions on wwww.ee.ic.ac.uk/pcheung/teaching/E2_experiment
module bin2bcd_8 (B, BCD_0, BCD_1, BCD_2);
input [7:0] B; // binary input number
output [3:0] BCD_0, BCD_1, BCD_2; // BCD digit LSD to MSD
wire [3:0] w1,w2,w3,w4,w5,w6,w7;
wire [3:0] a1,a2,a3,a4,a5,a6,a7;
// Instantiate a tree of add3-if-greater than or equal to 5 cells
// ... input is w_n, and output is a_n
add3_ge5 A1 (w1,a1);
add3_ge5 A2 (w2,a2);
add3_ge5 A3 (w3,a3);
add3_ge5 A4 (w4,a4);
add3_ge5 A5 (w5,a5);
add3_ge5 A6 (w6,a6);
add3_ge5 A7 (w7,a7);
// wire the tree of add3 modules together
assign w1 = {1'b0, B[7:5]}; // wn is the input port to module An
assign w2 = {a1[2:0], B[4]};
assign w3 = {a2[2:0], B[3]};
assign w4 = {1'b0, a1[3], a2[3], a3[3]};
assign w5 = {a3[2:0], B[2]};
assign w6 = {a4[2:0], a5[3]};
assign w7 = {a5[2:0], B[1]};
// connect up to four BCD digit outputs
assign BCD_0 = {a7[2:0],B[0]};
assign BCD_1 = {a6[2:0],a7[3]};
assign BCD_2 = {2'b0,a4[3],a6[3]};
endmodule
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