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// Top-level module
module foo (
LED1,
LED2,
BUT1,
BUT2,
SYSCLK
);
output LED1;
output LED2;
input BUT1;
input BUT2;
input SYSCLK;
// 2-bit counter register
reg [1:0] val;
initial val = 2'b00;
// Wires for debounced button signals
wire db_but1;
wire db_but2;
// Instantiate debounce modules for each button.
// Adjust the DEBOUNCE_LIMIT parameter as needed based on SYSCLK frequency.
debounce #(
.DEBOUNCE_LIMIT(500000)
) debounce_but1 (
.clk(SYSCLK),
.button(BUT1),
.db_out(db_but1)
);
debounce #(
.DEBOUNCE_LIMIT(500000)
) debounce_but2 (
.clk(SYSCLK),
.button(BUT2),
.db_out(db_but2)
);
// Edge detection registers to trigger a single count change per button press.
reg prev_db_but1;
reg prev_db_but2;
initial begin
prev_db_but1 = 1'b0;
prev_db_but2 = 1'b0;
end
// Drive LEDs from the counter bits.
assign LED1 = val[0];
assign LED2 = val[1];
// Synchronous logic to detect rising edges and update counter.
always @(posedge SYSCLK) begin
// If a rising edge is detected on db_but1, increment the counter.
if (db_but1 && !prev_db_but1) val <= val + 1;
// Else, if a rising edge is detected on db_but2, decrement the counter.
else if (db_but2 && !prev_db_but2) val <= val - 1;
// Store the current debounced states for edge detection on the next clock.
prev_db_but1 <= db_but1;
prev_db_but2 <= db_but2;
end
endmodule
// Debounce module written in plain Verilog.
module debounce (
clk,
button,
db_out
);
parameter DEBOUNCE_LIMIT = 500000; // Adjust as needed for your clock frequency.
input clk;
input button;
output db_out;
reg db_out;
reg [31:0] counter; // Counter width chosen to comfortably count up to DEBOUNCE_LIMIT.
reg button_sync;
initial begin
counter = 32'd0;
db_out = 1'b0;
button_sync = 1'b0;
end
always @(posedge clk) begin
// First, synchronize the raw button input to the clock domain.
button_sync <= button;
// If the synchronized value equals the debounced output,
// reset the counter.
if (button_sync == db_out) counter <= 32'd0;
else begin
// Otherwise, increment the counter.
counter <= counter + 1;
// If the counter reaches the limit, update the debounced output.
if (counter >= DEBOUNCE_LIMIT) begin
db_out <= button_sync;
counter <= 32'd0;
end
end
end
endmodule
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