自动售货机
if朴素方法
一种思路是用寄存器cnt记录已有的最小单位货币量，这里就是0.5
当d1时，cnt+1;d2时，cnt+2;d3时，cnt+4;
`timescale 1ns/1ns
module seller1(
input wire clk ,
input wire rst ,
input wire d1 ,
input wire d2 ,
input wire d3 ,
output reg out1,
output reg [1:0]out2
);
reg[2:0]cnt;
always@(posedge clk,negedge rst)begin
if(!rst)begin
cnt<=0;
out1<=0;
out2<=0;
end
else begin
if(d1)cnt<=cnt+1;
else if(d2)cnt<=cnt+2;
else if(d3)cnt<=cnt+4;
else if(cnt>=3)begin
out1<=1;
out2<=cnt-3;
cnt<=0;//记得复位为0，表示一个过程的结束
end
else begin
out1<=0;
out2<=0;
end//这里需要注意一定需要这一步，不然在不复位时，将保持一直输出1的状态
end
end
endmodule这里注意，d1,d2,d3都是以脉冲的形式，即只会接受一个时间步里，检测也都是
`timescale 1ns/1ns
module seller1(
input wire clk ,
input wire rst ,
input wire d1 ,
input wire d2 ,
input wire d3 ,
output reg out1,
output reg [1:0]out2
);
parameter S0 = 'd0, S1 = 'd1, S2 = 'd2, S3 = 'd3 , S4 = 'd4, S5 = 'd5 , S6 = 'd6;
reg [2:0] current_state;
reg [2:0] next_state;
wire [2:0] input_state;//将输入组合起来
assign input_state = {d1,d2,d3};
always@(posedge clk or negedge rst)begin
if(rst == 1'b0)begin
current_state <= S0;
end
else begin
current_state <= next_state;
end
end
always@(*)begin
case(current_state)
S0:begin
case(input_state)
3'b100:next_state = S1 ;
3'b010:next_state = S2 ;
3'b001:next_state = S4 ;
default:next_state = next_state;
endcase
end
S1:begin
case(input_state)
3'b100:next_state = S2 ;
3'b010:next_state = S3 ;
3'b001:next_state = S5 ;
default:next_state = next_state;
endcase
end
S2:begin
case(input_state)
3'b100:next_state = S3 ;
3'b010:next_state = S4 ;
3'b001:next_state = S6 ;
default:next_state = next_state;
endcase
end
default:begin
next_state = S0;
end
endcase
end
always@(posedge clk or negedge rst)begin
if(rst == 1'b0)begin
out1 <= 1'b0;
out2 <= 2'b0;
end
else begin
case(next_state)
S3: begin out1 <= 1'b1;out2 <= 2'b0; end
S4: begin out1 <= 1'b1;out2 <= 2'b1; end
S5: begin out1 <= 1'b1;out2 <= 2'b10; end
S6: begin out1 <= 1'b1;out2 <= 2'b11; end
default: begin out1 <= 1'b0;out2 <= 2'b0; end
endcase
end
end
endmodule状态机方法
采用MOORE状态机，即输出只与状态有关，而与当前输入信号无关
状态机的方式可以支持一次投入多枚硬币
MOORE三段
第一段：信号声明，状态定义，状态转换
第二段：由现态，依据输入信号确定次态
这里可以看出，如果一次投入多个硬币，可以进行转移与判断，只需在case里增添判断即可
第三段：依据次态确定输出信号
自动售货机（支持多物品售卖）
sel为0时买一块五，即第四个状态，s3;为1时买两块五，为第六个状态，s5
状态机
`timescale 1ns/1ns
module seller2(
input wire clk ,
input wire rst ,
input wire d1 ,
input wire d2 ,
input wire sel ,
output reg out1,
output reg out2,
output reg out3
);
//*************code***********//
parameter S0=0, S0_5=1, S1=2, S1_5=3, S2=4, S2_5=5, S3=6;
reg[2:0] state, nstate;
always@(posedge clk or negedge rst) begin
if(~rst)
state <= 0;
else
state <= nstate;
end
always@(*) begin
case(state)
S0 : nstate = d1? S0_5:
d2? S1:
nstate;
S0_5 : nstate = d1? S1:
d2? S1_5:
nstate;
S1 : nstate = d1? S1_5:
d2? S2:
nstate;
S1_5 : nstate = ~sel? S0:
d1? S2:
d2? S2_5:
nstate;
S2 : nstate = ~sel? S0:
d1? S2_5:
d2? S3:
nstate;
default: nstate = S0;
endcase
end
always@(*) begin
if(~rst) begin
{out1, out2, out3} = 3'b000;
end
else begin
case(state)
S0, S0_5, S1: {out1, out2, out3} = 0;
S1_5 : {out1, out2, out3} = ~sel? 3'b100: 3'b000;
S2 : {out1, out2, out3} = ~sel? 3'b101: 3'b000;
S2_5 : {out1, out2, out3} = ~sel? 3'b101: 3'b010;
S3 : {out1, out2, out3} = ~sel? 3'b101: 3'b011;
default : {out1, out2, out3} = 3'b000;
endcase
end
end
//*************code***********//
endmodule
上面为mealy型状态机，即输出取决于现态与输入信号
`timescale 1ns/1ns
module seller2(
input wire clk ,
input wire rst ,
input wire d1 ,
input wire d2 ,
input wire sel ,
output reg out1,
output reg out2,
output reg out3
);
parameter S0 = 'd0, S1 = 'd1, S2 = 'd2, S3 = 'd3 , S4 = 'd4, S5 = 'd5, S6 = 'd6;
reg [2:0] current_state;
reg [2:0] next_state;
wire [1:0] input_state;
assign input_state = {d1,d2};
always@(posedge clk or negedge rst)begin
if(rst == 1'b0)begin
current_state <= S0;
end
else begin
current_state <= next_state;
end
end
always@(*)begin
if (!sel) begin
case(current_state)
S0:begin
case(input_state)
2'b10 :next_state = S1 ;
2'b01 :next_state = S2 ;
default:next_state = next_state;
endcase
end
S1:begin
case(input_state)
2'b10 :next_state = S2 ;
2'b01 :next_state = S3 ;
default:next_state = next_state;
endcase
end
S2:begin
case(input_state)
2'b10 :next_state = S3 ;
2'b01 :next_state = S4 ;
default:next_state = next_state;
endcase
end
default: next_state = S0;
endcase
end
else begin
case(current_state)
S0:begin
case(input_state)
2'b10 :next_state = S1 ;
2'b01 :next_state = S2 ;
default:next_state = next_state;
endcase
end
S1:begin
case(input_state)
2'b10 :next_state = S2 ;
2'b01 :next_state = S3 ;
default:next_state = next_state;
endcase
end
S2:begin
case(input_state)
2'b10 :next_state = S3 ;
2'b01 :next_state = S4 ;
default:next_state = next_state;
endcase
end
S3:begin
case(input_state)
2'b10 :next_state = S4 ;
2'b01 :next_state = S5 ;
default:next_state = next_state;
endcase
end
S4:begin
case(input_state)
2'b10 :next_state = S5 ;
2'b01 :next_state = S6 ;
default:next_state = next_state;
endcase
end
default: next_state = S0;
endcase
end
end
always@(posedge clk or negedge rst)begin
if(rst == 1'b0)begin
out1 <= 1'b0;
out2 <= 1'b0;
out3 <= 1'b0;
end
else begin
if(!sel)begin
case (next_state)
S3: begin out1 <= 1'b1;out2 <= 1'b0;out3 <= 1'b0;end
S4: begin out1 <= 1'b1;out2 <= 1'b0;out3 <= 1'b1;end
default:begin out1 <= 1'b0;out2 <= 1'b0;out3 <= 1'b0;end
endcase
end
else begin
case (next_state)
S5: begin out1 <= 1'b0;out2 <= 1'b1;out3 <= 1'b0;end
S6: begin out1 <= 1'b0;out2 <= 1'b1;out3 <= 1'b1;end
default:begin out1 <= 1'b0;out2 <= 1'b0;out3 <= 1'b0;end
endcase
end
end
end
endmodule上面为标准的MOORE状态机代码，即输出只与次态有关
在状态转换中，一定要记得写
即相当于
后面的复位，不然没办法复位
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