This program is in verilog and need help to get it working
correctly. This is the code i have so far. Please help.
Simple testbench would be great. Thanks\


'define vend_a_drink {D,dispense,collect} = {IDLE,2'b11};
module drink_machine(nickel_in, dime_in, quarter_in,
collect, nickel_out, dime_out,
dispense, reset, clk) ;
parameter IDLE=0,FIVE=1,TEN=2,TWENTY_FIVE=3,
FIFTEEN=4,THIRTY=5,TWENTY=6,OWE_DIME=7;
input nickel_in, dime_in, quarter_in, reset, clk;
output collect, nickel_out, dime_out, dispense;
reg collect, nickel_out, dime_out, dispense;
reg [2:0] D, Q; /* state */
// synopsys state_vector Q
always @ ( nickel_in or dime_in or quarter_in or reset )
begin
nickel_out = 0;
dime_out = 0;
dispense = 0;
collect = 0;
if ( reset ) D = IDLE;
else begin
D = Q;
case ( Q )
IDLE:
if (nickel_in) D = FIVE;
else if (dime_in) D = TEN;
else if (quarter_in) D = TWENTY_FIVE;
FIVE:
if(nickel_in) D = TEN;
else if (dime_in) D = FIFTEEN;
else if (quarter_in) D = THIRTY;
TEN:
if (nickel_in) D = FIFTEEN;
else if (dime_in) D = TWENTY;
else if (quarter_in) 'vend_a_drink;
TWENTY_FIVE:
if( nickel_in) D = THIRTY;
else if (dime_in) 'vend_a_drink;
else if (quarter_in) begin
'vend_a_drink;
nickel_out = 1;
dime_out = 1;
end
FIFTEEN:
if (nickel_in) D = TWENTY;
else if (dime_in) D = TWENTY_FIVE;
else if (quarter_in) begin
'vend_a_drink;
nickel_out = 1;
end
THIRTY:
if (nickel_in) 'vend_a_drink;
else if (dime_in) begin
'vend_a_drink;
nickel_out = 1;
end
else if (quarter_in) begin
'vend_a_drink;
dime_out = 1;
D = OWE_DIME;
end
TWENTY:
if (nickel_in) D = TWENTY_FIVE;
else if (dime_in) D = THIRTY;
else if (quarter_in) begin
'vend_a_drink;
dime_out = 1;
end
OWE_DIME:
begin
dime_out = 1;
D = IDLE;
end
endcase
end
end
always @ (posedge clk ) begin
Q = D;
end
endmodule