使用Quartus-II 9.1SP2 + ModelSim 6.5b-Aletra + Altera DE2-115 FPGA開發平台，設計3Bit Counter為例(FPGA開發平台)
module DE2_115 (SW, LEDR, LEDG , CLOCK_50 ,KEY ,HEX0 ,HEX1 ,HEX2,HEX3,HEX4 ,HEX5 ,HEX6,HEX7, GPIO );
input [17:0] SW; // toggle switches
input [7:0] KEY; // Push bottom
input CLOCK_50; //Clock 27MHz , 50Mhz
output [17:0] LEDR; // red LEDS
output [8:0] LEDG; // green LEDs
output [6:0] HEX0,HEX1,HEX2,HEX3; //7-segment display
output [6:0] HEX4,HEX5,HEX6,HEX7; //7-segment display
inout [35:0] GPIO;
assign HEX0=7'b111_1111;
assign HEX1=7'b111_1111;
assign HEX2=7'b111_1111;
assign HEX3=7'b111_1111;
assign HEX4=7'b111_1111;
assign HEX5=7'b111_1111;
assign HEX6=7'b111_1111;
assign HEX7=7'b111_1111;
wire oClk_1MHz,oClk100K,oClk10K,oClk1K,oClk100,oClk10,oClk1 ;
MHz50_1MHz u1 (CLOCK_50,KEY[0],oClk_1MHz);
clk_1Hz u2 (oClk_1MHz,KEY[0],oClk100K,oClk10K,oClk1K,oClk100,oClk10,oClk1);
assign LEDR[17] = oClk1;
//module Counter_3bit(Q2, Q1, Q0, nCLK, RESETn);
Counter_3bit(LEDR[2], LEDR[1], LEDR[0], oClk1, SW[0]);
endmodule
module MHz50_1MHz(Clk_in , Clr , Clk_out); //除50
input Clk_in , Clr; // 一位元輸入
output reg Clk_out;
reg [4:0] cnt=5'b0_0000;
// counter size calculation according to input and output frequencies
parameter sys_clk = 50000000; // 50 MHz system clock
parameter clkout = 1000000; // 1 MHz clock output
parameter max = sys_clk / (2*clkout); // max-counter size
always@(posedge Clk_in or negedge Clr ) begin
if (~Clr)
begin
cnt <= 0;
end
else if (cnt == max-1 )
begin
cnt <= 0;
Clk_out <= ~Clk_out;
end
else
begin
cnt <= cnt + 1'd1;
end
end
endmodule
// Ch10 clk_1Hz.v
// 由 10M Hz 除頻至 1 Hz
module clk_1Hz (Clk1M,Clr,Clk100K,Clk10K,Clk1K,Clk100,Clk10,Clk1);
input Clk1M,Clr; // 一位元輸入
output Clk100K,Clk10K,Clk1K,Clk100,Clk10,Clk1; // 一位元輸出
div10 D2 (Clk1M , Clr, Clk100K);
div10 D3 (Clk100K, Clr, Clk10K );
div10 D4 (Clk10K , Clr, Clk1K );
div10 D5 (Clk1K , Clr, Clk100 );
div10 D6 (Clk100 , Clr, Clk10 );
div10 D7 (Clk10 , Clr, Clk1 );
endmodule
// Ch10 div10.v
// 除頻 /10
module div10 (Clk_i,Clr,Clk_o);
input Clk_i,Clr; // 一位元輸入
output Clk_o; // 一位元輸出
reg Clk_o; // 宣告為暫存器資料
reg [3:0] Q; // 宣告為暫存器資料
// MOD-10 (BCD) 除頻
always@ (posedge Clk_i or negedge Clr)
if (~Clr )
Q = 0;
else if (Q == 9)
Q = 0;
else
Q = Q + 1;
// 形成對稱方波
always@ (Q)
if (Q <= 4)
Clk_o = 0;
else
Clk_o = 1;
endmodule
module Counter_3bit(Q2, Q1, Q0, nCLK, RESETn);
output Q2;
output Q1;
output Q0;
input nCLK;
input RESETn;
wire Q2n;
wire Q1n;
wire Q0n;
wire J0;
wire J1;
wire J2;
and(J2, Q1, Q0n);
and(J1, Q0, Q2n);
and(J0, Q1n, Q2n);
jk_flip_flop_edge_triggered jkff0(Q0, Q0n, nCLK, J0, 1'b1, RESETn);
jk_flip_flop_edge_triggered jkff1(Q1, Q1n, nCLK, J1, 1'b1, RESETn);
jk_flip_flop_edge_triggered jkff2(Q2, Q2n, nCLK, J2, 1'b1, RESETn);
endmodule // counter
module jk_flip_flop_edge_triggered(Q, Qn, C, J, K, RESETn);
output Q;
output Qn;
input C;
input J;
input K;
input RESETn;
wire Kn; // The complement of the K input.
wire D;
wire D1; // Data input to the D latch.
wire Cn; // Control input to the D latch.
wire Cnn; // Control input to the SR latch.
wire DQ; // Output from the D latch, inputs to the gated SR latch (S).
wire DQn; // Output from the D latch, inputs to the gated SR latch (R).
assign D1 = !RESETn ? 0 : D; // Upon reset force D1 = 0
not(Kn, K);
and(J1, J, Qn);
and(K1, Kn, Q);
or(D, J1, K1);
not(Cn, C);
not(Cnn, Cn);
d_latch dl(DQ, DQn, Cn, D1);
sr_latch_gated sr(Q, Qn, Cnn, DQ, DQn);
endmodule // jk_flip_flop_edge_triggered
module d_latch(Q, Qn, G, D);
output Q;
output Qn;
input G;
input D;
wire Dn;
wire D1;
wire Dn1;
not(Dn, D);
and(D1, G, D);
and(Dn1, G, Dn);
nor(Qn, D1, Q);
nor(Q, Dn1, Qn);
endmodule // d_latch
module sr_latch_gated(Q, Qn, G, S, R);
output Q;
output Qn;
input G;
input S;
input R;
wire S1;
wire R1;
and(S1, G, S);
and(R1, G, R);
nor(Qn, S1, Q);
nor(Q, R1, Qn);
endmodule // sr_latch_gated
