用Verilog写I2C代码
时间: 2024-01-26 13:04:45 浏览: 21
以下是一个简单的Verilog代码示例,用于实现I2C协议的主机读取从机的操作。这个例子假设I2C总线上只有一个从机设备。
```verilog
module i2c_master (
input clk,
input reset,
output reg sda,
output reg scl
);
// 定义I2C协议的时序参数
parameter START_TIME = 50;
parameter STOP_TIME = 50;
parameter BIT_TIME = 50;
// 定义I2C总线的状态
parameter IDLE = 2'b00;
parameter START = 2'b01;
parameter STOP = 2'b10;
parameter TRANSMIT = 2'b11;
// 定义I2C总线的状态寄存器和计数器
reg [1:0] state = IDLE;
reg [5:0] count;
// 定义I2C数据寄存器和地址寄存器
reg [7:0] data_reg;
reg [6:0] addr_reg;
// 定义从机ACK标志
reg ack;
// 定义I2C状态机
always @(posedge clk) begin
if (reset) begin
state <= IDLE;
count <= 0;
sda <= 1;
scl <= 1;
end else begin
case (state)
IDLE: begin
sda <= 1;
scl <= 1;
if (count == 0) begin
state <= START;
count <= START_TIME;
end else begin
count <= count - 1;
end
end
START: begin
sda <= 0;
scl <= 0;
if (count == 0) begin
state <= TRANSMIT;
count <= BIT_TIME;
end else begin
count <= count - 1;
end
end
TRANSMIT: begin
if (count == 0) begin
if (addr_reg[6] == 1) begin
state <= STOP;
count <= STOP_TIME;
end else begin
state <= IDLE;
count <= BIT_TIME;
end
end else begin
if (addr_reg[7] == 1) begin
sda <= data_reg[7];
data_reg <= data_reg << 1;
end else begin
sda <= addr_reg[0];
addr_reg <= addr_reg >> 1;
end
scl <= 0;
count <= BIT_TIME;
end
end
STOP: begin
sda <= 1;
scl <= 1;
state <= IDLE;
count <= BIT_TIME;
end
default: begin
state <= IDLE;
count <= BIT_TIME;
end
endcase
end
end
// 定义读取从机数据的任务
task i2c_read;
input [6:0] addr;
output reg [7:0] data;
begin
addr_reg <= {addr, 1'b0};
state <= START;
count <= START_TIME;
ack <= 0;
repeat (8) begin
@(posedge scl);
end
if (ack == 0) begin
state <= START;
count <= START_TIME;
repeat (8) begin
@(posedge scl);
data_reg <= {data_reg[6:0], sda};
end
data <= data_reg;
end
state <= STOP;
count <= STOP_TIME;
end
endtask
// 定义接收从机数据的任务
task i2c_write;
input [6:0] addr;
input [7:0] data;
begin
addr_reg <= {addr, 1'b0};
data_reg <= data;
state <= START;
count <= START_TIME;
ack <= 0;
repeat (8) begin
@(posedge scl);
end
if (ack == 0) begin
state <= TRANSMIT;
count <= BIT_TIME;
repeat (8) begin
@(posedge scl);
end
end
state <= STOP;
count <= STOP_TIME;
end
endtask
// 监听从机的ACK信号
always @(posedge scl) begin
if (state == TRANSMIT && count == 0) begin
ack <= sda;
scl <= 1;
end
end
endmodule
```
这个例子中,我们定义了一个i2c_master模块,该模块包含了I2C协议的时序参数、总线状态、状态寄存器、计数器、数据寄存器、地址寄存器、从机ACK标志以及状态机等元素。在状态机中,我们根据I2C协议的时序要求,依次发送起始信号、设备地址、数据、停止信号,并且根据从机的ACK信号来确认每个操作是否成功。同时,我们也定义了两个任务i2c_read和i2c_write,分别用于读取从机数据和向从机发送数据。这个例子可以作为I2C协议的参考实现,但是实际应用中需要根据具体的需求对代码进行修改。