逐行解释代码module rx_state( clk, rst_n, rx, state, idle_out, lock_out, buff ); input clk, rst_n; input rx; output reg [7:0] buff; output reg [3:0] state; output reg idle_out, lock_out; reg neg_detect; reg [3:0] state_n; reg [7:0] buff_n; reg [49:0] cnt, cnt_n; reg [1:0] shift, shift_n; ///////////////// parameter FULL_T = 50000000/9600-1; parameter HALF_T = FULL_T/2; parameter S_IDLE = 0; parameter S_STAR = 1; parameter S_BIT0 = 2; parameter S_BIT1 = 3; parameter S_BIT2 = 4; parameter S_BIT3 = 5; parameter S_BIT4 = 6; parameter S_BIT5 = 7; parameter S_BIT6 = 8; parameter S_BIT7 = 9; parameter S_STOP = 10; //state machine always @ (posedge clk or negedge rst_n) begin if (!rst_n) state <= 0; else state <= state_n; end always @ (*) begin case (state) default : state_n = S_IDLE; S_IDLE : begin if (neg_detect) state_n = S_STAR; else state_n = S_IDLE; end S_STAR : begin if (cnt == FULL_T) state_n = S_BIT0; else state_n = S_STAR; end S_BIT0 : begin if (cnt == FULL_T) state_n = S_BIT1; else state_n = S_BIT0; end S_BIT1 : begin if (cnt == FULL_T) state_n = S_BIT2; else state_n = S_BIT1; end S_BIT2 : begin if (cnt == FULL_T) state_n = S_BIT3; else state_n = S_BIT
时间: 2024-02-10 18:22:40 浏览: 36
3; end S_BIT3 : begin if (cnt == FULL_T) state_n = S_BIT4; else state_n = S_BIT3; end S_BIT4 : begin if (cnt == FULL_T) state_n = S_BIT5; else state_n = S_BIT4; end S_BIT5 : begin if (cnt == FULL_T) state_n = S_BIT6; else state_n = S_BIT5; end S_BIT6 : begin if (cnt == FULL_T) state_n = S_BIT7; else state_n = S_BIT6; end S_BIT7 : begin if (cnt == FULL_T) state_n = S_STOP; else state_n = S_BIT7; end S_STOP : begin state_n = S_IDLE; end endcase end always @ (posedge clk or negedge rst_n) begin if (!rst_n) neg_detect <= 0; else neg_detect <= rx; end always @ (posedge clk) begin if (state == S_STAR) cnt_n <= 0; else cnt_n <= cnt + 1; end always @ (posedge clk or negedge rst_n) begin if (!rst_n) shift <= 0; else shift <= shift_n; end always @ (posedge clk) begin case (state) default : begin buff_n <= 8'b0; idle_out <= 1; lock_out <= 0; end S_IDLE : begin buff_n <= 8'b0; idle_out <= 1; lock_out <= 0; end S_STAR : begin buff_n <= 8'b0; idle_out <= 0; lock_out <= 0; end S_BIT0 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT1 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT2 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT3 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT4 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT5 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT6 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_BIT7 : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 0; end S_STOP : begin buff_n <= {1'b0, rx}; idle_out <= 0; lock_out <= 1; end endcase end always @ (posedge clk or negedge rst_n) begin if (!rst_n) buff <= 8'b0; else if (shift) buff <= buff_n; end always @ (posedge clk) begin if (state == S_STOP) shift_n <= 0; else shift_n <= shift + 1; end
以上是一个 Verilog HDL 语言写的模块 rx_state,主要用于串口通信接收数据时的状态机控制。其中 clk、rst_n、rx 分别为时钟、复位和串口接收信号,state、idle_out、lock_out 和 buff 分别为状态、空闲输出、锁定输出和接收数据缓存。这个模块使用了参数 FULL_T 和 HALF_T,分别表示一个完整的串口位时间和半个串口位时间。状态机中定义了若干个状态,包括 S_IDLE、S_STAR、S_BIT0 到 S_BIT7 和 S_STOP。在状态机中,通过计数器 cnt 实现了对每个串口位的计时,通过 buff_n 记录接收到的数据,在状态机中控制 state 和 state_n 的转移。同时,通过 neg_detect 对串口接收信号进行检测,通过 shift_n 和 buff_n 实现对接收数据的缓存和输出控制。