题解 | #自动售卖机#
自动售卖机
https://www.nowcoder.com/practice/487953e6d3e3434988e0dd6960b6c9f8
`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 = 1'b0, B_5_STATE = 1'b1;
reg curr_state, next_state;
always @(posedge clk or negedge rst_n) begin
if(~rst_n) begin
curr_state <= IDLE;
end
else begin
curr_state <= next_state;
end
end
always @(*) begin
case(curr_state)
IDLE: begin
if(sel == 1'b1 && din == 2'd1) begin
next_state = B_5_STATE;
end
else begin
next_state = IDLE;
end
end
B_5_STATE: begin
if(sel == 1'b1 && din == 2'd1) begin
next_state = IDLE;
end
else if(sel == 1'b1 && din == 2'd2) begin
next_state = IDLE;
end
else begin
drinks_out = 0;
change_out = 0;
next_state = B_5_STATE;
end
end
endcase
end
always @(posedge clk or negedge rst_n) begin
if(~rst_n) begin
drinks_out = 0;
change_out = 0;
end
else begin
case(curr_state)
IDLE: begin
if(sel == 1'b0 && din == 2'd0) begin
drinks_out = 0;
change_out = 0;
end
else if(sel == 1'b0 && din == 2'd1) begin
drinks_out = 1;
change_out = 0;
end
else if(sel == 1'b0 && din == 2'd2)begin
drinks_out = 1;
change_out = 1;
end
else if(sel == 1'b1 && din == 2'd0) begin
drinks_out = 0;
change_out = 0;
end
else if(sel == 1'b1 && din == 2'd1) begin
drinks_out = 0;
change_out = 0;
end
else if(sel == 1'b1 && din == 2'd2) begin
drinks_out = 2;
change_out = 0;
end
else begin
drinks_out = 0;
change_out = 0;
end
end
B_5_STATE: begin
if(sel == 1'b1 && din == 2'd0) begin
drinks_out = 0;
change_out = 0;
end
else if(sel == 1'b1 && din == 2'd1) begin
drinks_out = 2;
change_out = 0;
end
else if(sel == 1'b1 && din == 2'd2) begin
drinks_out = 2;
change_out = 1;
end
else begin
drinks_out = 0;
change_out = 0;
end
end
endcase
end
end
endmodule
前期被题目坑了，“sel信号会先于din信号有效”这句话让我误以为sel信号比din信号早一个周期。。。。。
