FPGA实现UART协议的接收与发送

**FPGA实现UART协议的接收与发送**

UART（Universal Asynchronous Receiver-Transmitter）是一种常见的串行通信协议，用于在计算机之间传输数据。FPGA（Field-Programmable Gate Array）是可以根据需要重新配置的逻辑门阵列，可以用来实现UART协议的接收和发送功能。在本文中，我们将介绍如何使用Verilog语言在FPGA上实现UART协议的接收和发送。

**UART协议概述**

UART协议是一种异步通信协议，主要用于串行传输数据。它通过一个单独的信号线（TXD）来传输数据，从而减少了总线宽度。UART协议使用以下几个信号：

* **RXD**：接收数据信号* **TXD**：发送数据信号* **CTS**：清除终端信号* **RTS**：请求终端信号**FPGA实现UART协议的接收和发送**

在本节中，我们将使用Verilog语言来实现UART协议的接收和发送功能。

### UART接收器UART接收器负责从RXD信号中读取数据。我们可以使用一个状态机来实现这个功能。

verilogmodule uart_receiver(
 input wire clk,
 input wire rst,
 input wire rxd,
 output reg [7:0] data);

reg [3:0] state;
reg [7:0] data;

always @(posedge clk) begin if (rst) begin state <=4'd0;
 data <=8'h00;
 end else begin case (state)
4'd0: begin if (~rxd) begin state <=4'd1;
 end end4'd1: begin if (rxd) begin state <=4'd2;
 end end4'd2: begin data[0] <= rxd;
 state <=4'd3;
 end4'd3: begin if (~rxd) begin state <=4'd4;
 end else begin state <=4'd1;
 end end default: state <=4'd0;
 endcase endendassign data = {data[7:0]};
endmodule

verilogmodule uart_transmitter(
 input wire clk,
 input wire rst,
 input wire [7:0] data,
 output reg txd);

reg [3:0] state;
reg [7:0] data;

always @(posedge clk) begin if (rst) begin state <=4'd0;
 txd <=1'b0;
 end else begin case (state)
4'd0: begin if (~data[7]) begin state <=4'd1;
 end end4'd1: begin if (data[7]) begin txd <=1'b1;
 state <=4'd2;
 end else begin state <=4'd0;
 end end4'd2: begin if (~data[6]) begin state <=4'd3;
 end end4'd3: begin if (data[6]) begin txd <=1'b1;
 state <=4'd4;
 end else begin state <=4'd0;
 end end default: state <=4'd0;
 endcase endendassign txd = ~txd;
endmodule

verilogmodule uart(
 input wire clk,
 input wire rst,
 output reg [7:0] data,
 output reg txd);

uart_receiver u1 (
 .clk(clk),
 .rst(rst),
 .rxd(rx_d),
 .data(data)
);

uart_transmitter u2 (
 .clk(clk),
 .rst(rst),
 .data(data),
 .txd(txd)
);
endmodule

verilogmodule uart_test(
 input wire clk,
 input wire rst,
 output reg [7:0] data,
 output reg txd);

uart u1 (
 .clk(clk),
 .rst(rst),
 .data(data),
 .txd(txd)
);

reg [7:0] data_in =8'h12;
reg [3:0] state;

always @(posedge clk) begin if (rst) begin state <=4'd0;
 data <=8'h00;
 end else begin case (state)
4'd0: begin if (~data_in[7]) begin state <=4'd1;
 end end4'd1: begin if (data_in[7]) begin data[0] <= data_in[0];
 state <=4'd2;
 end else begin state <=4'd0;
 end end4'd2: begin if (~data_in[6]) begin state <=4'd3;
 end end4'd3: begin if (data_in[6]) begin data[1] <= data_in[1];
 state <=4'd4;
 end else begin state <=4'd0;
 end end default: state <=4'd0;
 endcase endendassign txd = ~txd;

initial begin rst <=1'b1;
 #10;
 rst <=1'b0;
 data_in <=8'h12;
 #100;
 data_in <=8'h34;
 #100;
 data_in <=8'h56;
endendmodule

verilogmodule uart_testbench(
 input wire clk,
 output reg [7:0] data,
 output reg txd);

uart u1 (
 .clk(clk),
 .data(data),
 .txd(txd)
);

reg [7:0] data_in =8'h12;
reg [3:0] state;

always @(posedge clk) begin if (rst) begin state <=4'd0;
 data <=8'h00;
 end else begin case (state)
4'd0: begin if (~data_in[7]) begin state <=4'd1;
 end end4'd1: begin if (data_in[7]) begin data[0] <= data_in[0];
 state <=4'd2;
 end else begin state <=4'd0;
 end end4'd2: begin if (~data_in[6]) begin state <=4'd3;
 end end4'd3: begin if (data_in[6]) begin data[1] <= data_in[1];
 state <=4'd4;
 end else begin state <=4'd0;
 end end default: state <=4'd0;
 endcase endendassign txd = ~txd;

initial begin rst <=1'b1;
 #10;
 rst <=1'b0;
 data_in <=8'h12;
 #100;
 data_in <=8'h34;
 #100;
 data_in <=8'h56;
endendmodule

verilogmodule uart_testbench(
 input wire clk,
 output reg [7:0] data,
 output reg txd);

uart u1 (
 .clk(clk),
 .data(data),
 .txd(txd)
);

reg [7:0] data_in =8'h12;
reg [3:0] state;

always @(posedge clk) begin if (rst) begin state <=4'd0;
 data <=8'h00;
 end else begin case (state)
4'd0: begin