状态机基础知识
VL25 输入序列连续的序列检测
`timescale 1ns/1ns
module sequence_detect(
input clk,
input rst_n,
input a,
output reg match
);
//这题就是普通的状态机，需要注意的是：
// @当输入不能跳转到下一个状态时，可以复用前面的序列
// @这题是的Moore状态机，输出只和当前状态有关
//定义状态空间(状态参数、状态寄存器)
parameter IDLE = 0 ;
parameter S0 = 1 ;
parameter S1 = 2 ;
parameter S2 = 3 ;
parameter S3 = 4 ;
parameter S4 = 5 ;
parameter S5 = 6 ;
parameter S6 = 7 ;
parameter S7 = 8 ;
reg [3:0] curr_state,next_state;
// 1.打一拍更新现态
always@(posedge clk or negedge rst_n) begin
if(~rst_n) begin
curr_state <= IDLE;
end else begin
curr_state <= next_state;
end
end
// 2.组合逻辑根据现态和输入生成次态
always@(*) begin
case(curr_state)
IDLE : next_state = (a == 0) ? S0 : IDLE ;
S0 : next_state = (a == 1) ? S1 : S0 ;
S1 : next_state = (a == 1) ? S2 : S0 ;
S2 : next_state = (a == 1) ? S3 : S0 ;
S3 : next_state = (a == 0) ? S4 : S0 ;
S4 : next_state = (a == 0) ? S5 : S1 ;
S5 : next_state = (a == 0) ? S6 : S1 ;
S6 : next_state = (a == 1) ? S7 : S1 ;
S7 : next_state = (a == 0) ? IDLE:S2 ;
default: next_state = IDLE;
endcase
end
// 3.Moore型FSM，根据当前状态生成输出
always@(posedge clk or negedge rst_n) begin
if(~rst_n) begin
match <= 0;
end else if(curr_state == S7) begin
match <= 1;
end else begin
match <= 0;
end
end
endmodule
VL26 含有无关项的序列检测
两种方法：
法一、用寄存器维护一个存储序列的寄存器
法二、用状态机来做
这里我用寄存器来做。
`timescale 1ns/1ns
module sequence_detect(
input clk,
input rst_n,
input a,
output reg match
);
reg [8:0] curr_seq;
// 1.维护存储序列的寄存器
always@(posedge clk or negedge rst_n) begin
if(~rst_n) begin
curr_seq <= 9'bxxx_xxx_xxx;
end else begin
curr_seq <= {curr_seq[7:0],a};
end
end
// 2.判断序列是否模式匹配
always@(posedge clk or negedge rst_n) begin
if(~rst_n) begin
match <= 0;
end else if(curr_seq[2:0] == 3'b110 && curr_seq[8:6] == 3'b011) begin
match <= 1;
end else begin
match <= 0;
end
end
endmodule
VL27 不重叠序列检测
通过计数器进行分组序列检测，每组判断一次
注意点：
- 计数器计算到6时才进行判断
- 在分组中一旦错误，直接FAIL
- 注意需要处理FAIL的状态跳转
- 注意寄存器的初始值,要计数6个就1~6,初值为0
module sequence_detect(
input clk,
input rst_n,
input data,
output reg match,
output reg not_match
);
//分组序列检测
//注意点：
//@计数器计算到6时才进行判断
//@在分组中一旦错误，直接FAIL
//@注意需要处理FAIL的状态跳转
//@注意寄存器的初始值,要计数6个就1~6,初值为0
// 定义状态空间和状态寄存器
parameter IDLE = 0 ,
S1 = 1 ,
S2 = 2 ,
S3 = 3 ,
S4 = 4 ,
S5 = 5 ,
S6 = 6 ,
FAIL = 7 ;
reg [2:0] curr_state,next_state;
reg [2:0] cnt;
// 利用计数器进行分组
always@(posedge clk or negedge rst_n ) begin
if(~rst_n) begin
cnt <= 'b0;
end else begin
if(cnt == 3'd6) cnt <= 'b1;
else cnt <= cnt + 1;
end
end
// 1.次态更新现态
always@(posedge clk or negedge rst_n) begin
if(~rst_n) begin
curr_state = IDLE;
end else begin
curr_state = next_state;
end
end
// 2.组合逻辑生成次态
always@(*) begin
case(curr_state)
IDLE : next_state = (data==0) ? S1 : FAIL ;
S1 : next_state = (data==1) ? S2 : FAIL ;
S2 : next_state = (data==1) ? S3 : FAIL ;
S3 : next_state = (data==1) ? S4 : FAIL ;
S4 : next_state = (data==0) ? S5 : FAIL ;
S5 : next_state = (data==0) ? S6 : FAIL ;
S6 : next_state = (data==0) ? S1 : FAIL ;
FAIL : next_state = (cnt == 6 && data ==0) ? S1 : FAIL;
default : next_state = IDLE ;
endcase
end
// 3.根据现态生成输出，波形match没有打拍直接组合逻辑输出
always@(*) begin
if(~rst_n) begin
match <= 0;
not_match <= 0;
end
else if(cnt == 6 ) begin
if(curr_state == S6) begin
match <= 1;
not_match <= 0;
end else begin
match <= 0;
not_match <= 1;
end
end
else begin
match <= 0;
not_match <= 0;
end
end
endmodule
VL28 输入序列不连续的序列检测
`timescale 1ns/1ns
module sequence_detect(
input clk,
input rst_n,
input data,
input data_valid,
output reg match
);
//输入数据不连续的序列检测，在状态跳转时需要考虑data_valid
parameter IDLE = 5'b00001;
parameter S1 = 5'b00010;
parameter S2 = 5'b00100;
parameter S3 = 5'b01000;
parameter S4 = 5'b10000;
parameter STATE_WIDTH = 5;
reg [STATE_WIDTH - 1 : 0] cs;
reg [STATE_WIDTH - 1 : 0] ns;
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
cs <= IDLE;
end
else begin
cs <= ns;
end
end
always@(*) begin
case(cs)
IDLE : begin
if( data_valid ) begin
ns = data == 0 ? S1 : IDLE ;
end
else begin
ns = cs;
end
end
S1 : begin
if( data_valid ) begin
ns = data == 1 ? S2 : S1;
end
else begin
ns = cs;
end
end
S2 : begin
if( data_valid ) begin
ns = data == 1 ? S3 : S1;
end
else begin
ns = cs;
end
end
S3 : begin
if( data_valid ) begin
ns = IDLE;
end
else begin
ns = cs;
end
end
endcase
end
always@(posedge clk or negedge rst_n) begin
if(!rst_n) begin
match <= 0;
end
else begin
if(cs == S3 && data == 0 && data_valid == 1) begin
match <= 1;
end
else begin
match <= 0;
end
end
end
endmodule
