2Write a test bench to test the decbouncer 3Simulate to conf

2.Write a test bench to test the decbouncer

3.Simulate to confirm the result.

State 0 Button -1 delays 250 000 State 1 k delay State 2 1 Button -1 State 3 Button delay 250 000 State 4 delay 0 State 5 Button -0 State 6 debounced 1 delay delay 1 NOTE: The debounced output is combinational, and should be \"1\' when state 6, else it should be zero delay delay 1

Solution

module debouncing(
input clock,
input reset,
input button,
output reg out
);

localparam N = 19; //for a 10ms tick

reg [N-1:0]count;
wire tick;


// the counter that will generate the tick.

always @ (posedge clock or posedge reset)
begin
if(reset)
count <= 0;
else
count <= count + 1;
end

assign tick = &count; //AND every bit of count with itself. Tick will only go high when all 19 bits of count are 1, i.e. after 10ms

// now for the debouncing FSM

localparam[2:0] //defining the various states to be used
state0 = 3\'b000,
state1 = 3\'b001,
state2 = 3\'b010,
state3 = 3\'b011,
one = 3\'b100,
state4 = 3\'b101,
state5 = 3\'b110,
state6 = 3\'b111;

reg [2:0]state_reg;
reg [2:0]state_next;

always @ (posedge clock or posedge reset)
begin
if (reset)
state_reg <= state0;
else
state_reg <= state_next;
end


always @ (*)
begin
state_next <= state_reg; // to make the current state the default state
out <= 1\'b0; // default output low

case(state_reg)
state0:
if (button) //if button is detected go to next state state1
state_next <= state1;
state1:
if (~button) //while here if button goes back to state0 then input is not yet stable and go back to state state0
state_next <= state0;
else if (tick) //but if button remains high even after 10 ms, go to next state state2.
state_next <= state2;
state2:
if (~button) //while here if button goes back to state0 then input is not yet stable and go back to state state0
state_next <= state0;
else if (tick) //else if after 20ms (10ms + 10ms) button is still high go to state3
state_next <= state3;
state3:
if (~button) //while here if button goes back to state0 then input is not yet stable and go back to state state0
state_next <= state0;
else if (tick) //and finally even after 30 ms input stays high then it is stable enough to be considered a valid input, go to state one
state_next <= one;

one: //debouncing eliminated make output high, now here I\'ll check for bouncing when button is released
begin
out <= 1\'b1;
if (~button) //if button appears to be released go to next state state4
state_next <= state4;
end
state4:
if (button) //while here if button goes back to high then input is not yet stable and go back to state one
state_next <= one;
else if (tick) //else if after 10ms it is still high go to next state state5
state_next <= state5;
state5:
if (button) //while here if button goes back to high then input is not yet stable and go back to state one
state_next <= one;
else if (tick) //else if after 20ms it is still high go to next state state6
state_next <= state6;
state6:
if (button) //while here if button goes back to high then input is not yet stable and go back to state one
state_next <= one;
else if (tick) //after 30 ms if button is low it has actually been released and bouncing eliminated, go back to state0 state to wait for next input.
state_next <= state0;
default state_next <= state0;

endcase
end

endmodule