I have code and test bench however it is not working
porperly. Need help to get it working.

module fsm(clock,reset,coin,vend,state,change);
\\these are the inputs and the outputs.
input clock;
input reset;
input [2:0]coin;
output vend;
output [2:0]state;
output [2:0]change;
\\i need to define the registers as change,coin and vend
reg vend;
reg [2:0]change;
wire [2:0]coin;
\\my coins are declared as parameters to make reading
better.
parameter [2:0]NICKEL=3’b001;
parameter [2:0]DIME=3’b010;
parameter [2:0]NICKEL_DIME=3’b011;
parameter [2:0]DIME_DIME=3’b100;
parameter [2:0]QUARTER=3’b101;
\\MY STATES ARE ALSO PARAMETERS . I DONT WANT TO MAKE YOU
READ
\\IN MACHINE LANGUAGE
parameter [2:0]IDLE=3’b000;
parameter [2:0]FIVE=3’b001;
parameter [2:0]TEN=3’b010;
parameter [2:0]FIFTEEN=3’b011;
parameter [2:0]TWENTY=3’b100;
parameter [2:0]TWENTYFIVE=3’b101;
\\AS ALWAYS THE STATES ARE DEFINED AS REG
reg [2:0]state,next_state;
\\MY MACHINE WORKS ON STATE AND COIN
always @(state or coin)
begin
next_state=0; \\VERYFIRST NEXT STATE IS GIVEN ZERO
case(state)
IDLE: case(coin) \\THIS IS THE IDLE STATE
NICKEL: next_state=FIVE;
DIME: next_state=TEN;
QUARTER: next_state=TWENTYFIVE;
default: next_state=IDLE;
endcase
FIVE: case(coin) \\THIS IS THE SECOND STATE
NICKEL: next_state=TEN;
DIME: next_state=FIFTEEN;
QUARTER: next_state=TWENTYFIVE; //change=NICKEL
default: next_state=FIVE;
endcase
TEN: case(coin) \\THIS IS THE THIRD STATE
NICKEL: next_state=FIFTEEN;
DIME: next_state=TWENTY;
QUARTER: next_state=TWENTYFIVE; //change=DIME
default: next_state=TEN;
endcase
FIFTEEN: case(coin) \\THIS IS THE FOURTH STATE
NICKEL: next_state=TWENTY;
DIME: next_state=TWENTYFIVE;
QUARTER: next_state=TWENTYFIVE; //change==NICKEL_DIME
default: next_state=FIFTEEN;
endcase
TWENTY: case(coin) \\THIS IS THE FIFTH STATE
NICKEL: next_state=TWENTYFIVE;
DIME: next_state=TWENTYFIVE; //change=NICKEL
QUARTER: next_state=TWENTYFIVE; //change==DIME_DIME
default: next_state=TWENTY;
endcase
TWENTYFIVE: next_state=IDLE; \\THE NEXT STATE HERE IS THE
RESET
default : next_state=IDLE;
endcase
end
always @(clock)
begin \\WHENEVER I GIVE A RESET I HAVE TO MAKE THE STATE TO
IDLE AND VEND TO 1
if(reset) begin
state <= IDLE;
vend <= 1’b0;
// change <= 3’b000;
end \\THE CHANGE ALSO HAS TO BECOME NONE
else state <= next_state;
case (state) \\HERE WE DECIDE THE NEXT STATE
\\ALL THE STATES ARE DEFINED HERE AND THE OUTPUT IS ALSO
GIVEN
IDLE: begin vend <= 1’b0; change <=3’d0; end
FIVE: begin vend <= 1’b0; if (coin==QUARTER) change
<=NICKEL; else change <=3’d0; TEN: begin vend <= 1’b0; if
(coin==QUARTER) change <=DIME; else change <= 3’d0;
FIFTEEN : begin vend <= 1’b0; if (coin==QUARTER) change
<=NICKEL_DIME; else change TWENTY : begin vend <= 1’b0; if
(coin==DIME) change <=NICKEL; else if (coin==QUARTER)
TWENTYFIVE : begin vend <= 1’b1; change <=3’d0; end
default: state <= IDLE;
endcase
end
endmodule


module test;
\\THE INPUT IN THE FSM MODULE ARE REG HERE
reg clock,reset;
reg [2:0]coin;
\\THE OUTPUT IN THE FSM MODULE ARE WIRES HERE
wire vend;
wire [2:0]state;
wire [2:0]change;
\\THE PARAMETERS AGAIN FOR THE COIN AND STATE
parameter [2:0]IDLE=3’b000;
parameter [2:0]FIVE=3’b001;
parameter [2:0]TEN=3’b010;
parameter [2:0]FIFTEEN=3’b011;
parameter [2:0]TWENTY=3’b100;
parameter [2:0]TWENTYFIVE=3’b101;
parameter [2:0]NICKEL=3’b001;
parameter [2:0]DIME=3’b010;
parameter [2:0]NICKEL_DIME=3’b011;
parameter [2:0]DIME_DIME=3’b100;
parameter [2:0]QUARTER=3’b101;
\\I MONITOR THE TIME,DRINK,RESET,CLOCK,STATE AND CHANGE FOR
CHANGES.
initial begin
$display("Time\tcoin\tdrink\treset\tclock\tstate\tchange");
$monitor("%g\t%b\t%b\t%b\t%b\t%d\t%
d",$time,coin,vend,reset,clock,state,change);
\\NEW FEATURE: MY MACHINE HAS THE FACILITY TO DUMP
VARIABLES SO THAT
\\ I CAN VIEW THEM USING A VCD VIEWER.
$dumpvars;
$dumpfile("file.vcd"); // Dump output file.
\\THIS IS WHERE THE COINS ARE ADDED.
clock=0;
reset=1; \\FIRST LETS RESET THE MACHINE
#2 reset=0;
coin=NICKEL; \\CHECK FOR STATE 1
#2 reset=1; coin=2’b00;
#2 reset=0;
coin=DIME;
\\RESET AGAIN AND CHECK FOR STATE 2
#2 reset=1; coin=2’b00;
#2 reset=0;
\\RESET AGAIN AND CHECK FOR STATE 5
coin=QUARTER;
#2 reset=1; coin=2’b00;
#2 reset=0;
\\RESET AGAIN AND CHECK FOR STATE 5
coin=NICKEL;
#2 coin=NICKEL;
#2 coin=NICKEL;
#2 coin=NICKEL;
#2 coin=NICKEL;
#2 reset=1; coin=2’b00;
#2 reset=0;
\\RESET AGAIN AND CHECK FOR STATE 5 AND SO ON
coin=NICKEL;
#2 coin=DIME;
#2 coin=DIME;
#2 reset=1; coin=2’b00;
#2 reset=0;
coin=NICKEL;
#2 coin=DIME;
#2 coin=QUARTER;
#2 reset=1; coin=2’b00;
#2 reset=0;
coin=NICKEL;
#2 coin=NICKEL;
#2 coin=NICKEL;
#2 coin=DIME;
#2 reset=1; coin=2’b00;
#2 reset=0;
coin=NICKEL;
#2 coin=NICKEL;
#2 coin=NICKEL;
#2 coin=NICKEL;
#2 coin=DIME;
#2 reset=1; coin=2’b00;
#2 reset=0;
coin=NICKEL;
#2 coin=NICKEL;
#2 coin=QUARTER;
#2 reset=1; coin=2’b00;
#2 reset=0;
coin=NICKEL;
#2 coin=QUARTER;
#2 reset=1; coin=2’b00;
#2 $finish;
end
\\THE CLOCK NEEDS TO TICK EVERY 2 TIME UNIT
always
#1 clock=~clock;
//always @(state)
// coin=!coin;
initial begin
if (reset)
coin=2’b00;
end
\\THIS IS WHERE I INSTANTIATE THE MACHINE
fsm inst1(clock,reset,coin,vend,state,change);
endmodule