请给出verilog实现usart的代码
时间: 2024-02-16 15:04:35 浏览: 24
以下是一个基于Verilog的USART(通用同步/异步收发器)的简单代码示例:
```
module usart (
input clk,
input reset,
input enable,
input tx_start,
input [7:0] tx_data,
output reg tx_busy,
input rx_start,
output reg [7:0] rx_data,
output reg rx_done
);
// Internal registers
reg [7:0] tx_byte;
reg [7:0] rx_byte;
reg [2:0] state;
// Baud rate generator
parameter integer BAUD_RATE = 9600;
reg [15:0] baud_counter = 0;
reg baud_tick = 0;
// TX state machine
always @(posedge clk) begin
if (reset) begin
state <= 3'b000;
tx_byte <= 8'h00;
tx_busy <= 0;
end else begin
// Baud rate generator
if (baud_counter == {clk, 1'b0}) begin
baud_counter <= 16'd65535 - (clk / BAUD_RATE);
baud_tick <= 1;
end else begin
baud_counter <= baud_counter - 1;
baud_tick <= 0;
end
// TX state machine
case(state)
3'b000: begin
if (enable && tx_start) begin
tx_byte <= tx_data;
state <= 3'b001;
end
end
3'b001: begin
if (baud_tick) begin
tx_busy <= 1;
state <= 3'b010;
end
end
3'b010: begin
if (baud_tick) begin
tx_busy <= 1;
state <= 3'b011;
end
end
3'b011: begin
if (baud_tick) begin
tx_busy <= 1;
state <= 3'b100;
end
end
3'b100: begin
tx_busy <= 0;
state <= 3'b000;
end
endcase
end
end
// RX state machine
always @(posedge clk) begin
if (reset) begin
state <= 3'b000;
rx_byte <= 8'h00;
rx_done <= 0;
end else begin
// Baud rate generator
if (baud_counter == {clk, 1'b0}) begin
baud_counter <= 16'd65535 - (clk / BAUD_RATE);
baud_tick <= 1;
end else begin
baud_counter <= baud_counter - 1;
baud_tick <= 0;
end
// RX state machine
case(state)
3'b000: begin
if (rx_start) begin
state <= 3'b001;
end
end
3'b001: begin
if (baud_tick) begin
state <= 3'b010;
end
end
3'b010: begin
if (baud_tick) begin
rx_byte <= {rx_byte[6:0], rx_start};
state <= 3'b011;
end
end
3'b011: begin
if (baud_tick) begin
state <= 3'b100;
end
end
3'b100: begin
if (baud_tick) begin
rx_byte <= {rx_byte[6:0], rx_start};
rx_data <= rx_byte;
rx_done <= 1;
state <= 3'b000;
end
end
endcase
end
end
endmodule
```
在此代码中,USART的时钟由`clk`提供,复位信号由`reset`提供,使能信号由`enable`提供。当`tx_start`被触发时,`tx_data`的数据通过串行传输发送。当`rx_start`被触发时,接收的数据被存储在`rx_data`中,`rx_done`信号则指示接收完成。
在此代码中,使用了一个简单的状态机来控制数据的传输和接收。Baud rate generator用于产生与波特率匹配的定时信号。请注意,此代码仅用于示例目的。实际应用中,您需要根据您的设计需求进行修改。
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