// ----------------------------------------------------------

// 饮料单价 2 元，该售卖机只能接受 0.5 元、1 元的硬币,考虑找零和出货

// 3段式

//------------------------------------------------------------


module fsm_3
(
input Clk,
input Rst_n,
//input pi_input_0,
input pi_input_5,
input pi_input_10,

output reg po_out_money,
output reg po_out_water
);

parameter idle        =    3'd0;
parameter HALF_1    =    3'd1;
parameter ONE        =    3'd2;
parameter HALF_3    =    3'd3;

reg [3:0] state        ;
reg [3:0] next_state    ;


always@(posEdge Clk or negedge Rst_n)begin
if(Rst_n == 1'b0)
state <= IDLE;
else 
state <= next_state;
end


always@(*)begin

case(state)
    IDLE: 
        case({pi_input_5, pi_input_10})
        2'b10: next_state<= HALF_1;
        2'b01: next_state<= ONE;
        default: next_state<= IDLE;
        endcase            
    HALF_1: 
        case({pi_input_5, pi_input_10})
        2'b10: next_state<= ONE;
        2'b01: next_state<= HALF_3;
        default: next_state<= HALF_1;
        endcase
    ONE: 
        case({pi_input_5, pi_input_10})
        2'b10: next_state<= HALF_1;
        2'b01: next_state<= IDLE;
        default: next_state<= ONE;
        endcase
    HALF_3: 
        case({pi_input_5, pi_input_10})
        2'b10: next_state<= IDLE;
        2'b01: next_state<= IDLE;
        default: next_state<= HALF_3;
        endcase            
                        
    endcase


end

always@(posedge Clk or negedge Rst_n)begin
if(Rst_n == 1'b0)
    po_out_water <= 1'b0;
else if(((state == HALF_3) && (pi_input_5 == 1'b1)) || ((state == ONE) &amp;& (pi_input_10 == 1'b1)))
    po_out_water <= 1'b1;
else if((state == HALF_3) && (pi_input_10 == 1'b1)) begin
    po_out_water <= 1'b1;
    po_out_money <= pi_input_5;
    end
else begin
    po_out_water <= 1'b0;
    po_out_money <= 1'b0;
end    
end

endmodule 

`timescale 1ns/1ns

module tb_fsm_3;
reg clk;
reg Rst_n;
//reg in_0;
reg in_1;
reg in_2;
reg[1:0] in[2:0];
wire out_money;
wire out_water;

inITial begin 
in[0]=0;
in[1]=1;
in[2]=2;
clk = 1'b0;
Rst_n = 1'b0;
#10;
Rst_n = 1'b1;
in_1 = 1'b0;
in_2 = 1'b0;

end
 
always #10 clk = ~ clk;

always@(posedge clk or negedge Rst_n)begin
if(Rst_n == 1'b0)begin
    in_1 <= 1'b0;
    in_2 <= 1'b0;
    end
else begin
    {in_1,in_2}<=in[{$random}%3];
    end
 
end

fsm_3 fsm_3_inst
(
.Clk(clk),
.Rst_n(Rst_n),
//.pi_input_0(in_0),
.pi_input_5(in_1),
.pi_input_10(in_2),


.po_out_money(out_money),
.po_out_water(out_water)
);


endmodule