题解 | #自动售卖机#

自动售卖机

https://www.nowcoder.com/practice/487953e6d3e3434988e0dd6960b6c9f8

解法2：更简单的解法，状态机是一样的。

注意点：将两个输出合二为一、一起输出，更简单、

`timescale 1ns/1ns

module sale(
   input                clk   ,
   input                rst_n ,
   input                sel   ,//sel=0,5$dranks,sel=1,10&=$drinks
   input          [1:0] din   ,//din=1,input 5$,din=2,input 10$
 
   output   reg  [1:0] drinks_out,//drinks_out=1,output 5$ drinks,drinks_out=2,output 10$ drinks
   output	reg        change_out   
);
    parameter idle = 2'b01,
                drinkB_5 = 2'b10;
    reg [1:0] state, next_state;
    
    wire [2:0] comb;
    assign comb = {sel, din};
    
    always @ (posedge clk, negedge rst_n) begin
        if(!rst_n) begin
            state <= idle;
            
        end
        else begin
            state <= next_state;
        end
    end
    
    always @ (*) begin
        case(state) 
            idle: begin
                next_state = sel ? (din == 1 ? drinkB_5 : idle) : idle;
            end
            drinkB_5: begin
                next_state = din == 0 ? drinkB_5 : idle;
                
            end
            default: begin
                next_state = idle;
            end
        endcase
    end
    
    always @ (posedge clk, negedge rst_n) begin
        if(!rst_n) begin
            {drinks_out, change_out} <= 3'd0;
        end
        else begin
            if((state == drinkB_5)) begin
                if(comb == 3'b101) begin
                    {drinks_out, change_out} <= 3'b100;
                end
                else if(comb == 3'b110) begin
                    {drinks_out, change_out} <= 3'b101;
                end
                else begin
                    {drinks_out, change_out} <= 3'd0;
                end
            end
            else begin
                if(comb == 3'b001) begin
                    {drinks_out, change_out} <= 3'd010;
                end
                else if(comb == 3'b010) begin
                    {drinks_out, change_out} <= 3'd011;
                end
                else if (comb == 3'b110) begin
                    {drinks_out, change_out} <= 3'd100;
                end
                else begin
                    {drinks_out, change_out} <= 3'd0;
                end
            end
        end
    end
    
//     always @ (posedge clk, negedge rst_n) begin
//         if(!rst_n) begin
//             change_out <= 1'd0;
//         end
//         else if ((sel == 1'b0 && state == idle && din == 2) || (sel && state == drinkB_5 && din == 2)) begin
//                 change_out <= 1'd1;
//         end
//         else begin
//             change_out <= 1'd0;
//         end
//     end
    
    
    
    
endmodule

解法一：状态机。离大谱，状态机都不会写了

注意点：只有两个状态，需要考虑清楚

    parameter idle = 2'b01,
                drinkB_5 = 2'b10;

`timescale 1ns/1ns

module sale(
   input                clk   ,
   input                rst_n ,
   input                sel   ,//sel=0,5$dranks,sel=1,10&=$drinks
   input          [1:0] din   ,//din=1,input 5$,din=2,input 10$
 
   output   reg  [1:0] drinks_out,//drinks_out=1,output 5$ drinks,drinks_out=2,output 10$ drinks
   output	reg        change_out   
);
    parameter idle = 2'b01,
                drinkB_5 = 2'b10;
    reg [1:0] state, next_state;
    
    wire [2:0] comb;
    
    always @ (posedge clk, negedge rst_n) begin
        if(!rst_n) begin
            state <= idle;
            
        end
        else begin
            state <= next_state;
        end
    end
    
    always @ (*) begin
        case(state) 
            idle: begin
                next_state = sel ? (din == 1 ? drinkB_5 : idle) : idle;
            end
            drinkB_5: begin
                next_state = din == 0 ? drinkB_5 : idle;
                
            end
            default: begin
                next_state = idle;
            end
        endcase
    end
    
    always @ (posedge clk, negedge rst_n) begin
        if(!rst_n) begin
            drinks_out <= 2'd0;
        end
        else if (!sel) begin
            if((state == idle && din == 1) || (state == idle && din == 2)) begin
                drinks_out <= 2'd1;
            end
            else begin
                drinks_out <= 2'd0;
            end
        end
        else begin
            if((state == idle && din == 2) || (state == drinkB_5 && din == 2) || (state == drinkB_5 && din == 1)) begin
                drinks_out <= 2'd2;
            end
            else begin
                drinks_out <= 2'd0;
            end
        end
    end
    
    always @ (posedge clk, negedge rst_n) begin
        if(!rst_n) begin
            change_out <= 1'd0;
        end
        else if ((sel == 1'b0 && state == idle && din == 2) || (sel && state == drinkB_5 && din == 2)) begin
                change_out <= 1'd1;
        end
        else begin
            change_out <= 1'd0;
        end
    end
    
    
    
    
endmodule