verliog写个iic
时间: 2023-07-06 10:40:47 浏览: 37
好的,下面是一个使用 Verilog 实现 I2C 总线的代码示例:
```
module i2c_master (
input clk,
input rst,
output reg scl,
inout sda,
input [6:0] addr,
input [7:0] data_in,
output reg data_out,
output reg read,
output reg start,
output reg stop,
output reg busy,
output reg nack
);
parameter IDLE = 3'b000;
parameter START = 3'b001;
parameter ADDR = 3'b010;
parameter DATA = 3'b011;
parameter ACK = 3'b100;
parameter NACK = 3'b101;
parameter STOP = 3'b110;
parameter COMPLETE = 3'b111;
reg [2:0] state;
reg [7:0] shift_reg;
reg [3:0] bit_count;
assign sda = (state == DATA && shift_reg[bit_count] == 1'b0) ? 1'b0 : 1'b1;
always @(posedge clk) begin
if (rst) begin
scl <= 1'b1;
sda <= 1'b1;
state <= IDLE;
shift_reg <= 8'b00000000;
bit_count <= 4'd0;
read <= 1'b0;
start <= 1'b0;
stop <= 1'b0;
busy <= 1'b0;
nack <= 1'b0;
data_out <= 1'b0;
end else begin
case (state)
IDLE:
begin
if (start) begin
state <= START;
scl <= 1'b0;
shift_reg <= {7'b1111110, 1'b0};
bit_count <= 4'd0;
busy <= 1'b1;
end
end
START:
begin
if (scl == 1'b0) begin
scl <= 1'b1;
state <= ADDR;
end
end
ADDR:
begin
if (scl == 1'b0) begin
bit_count <= bit_count + 1;
if (bit_count == 4'd7) begin
if (read) begin
shift_reg <= {addr, 1'b1};
state <= START;
end else begin
shift_reg <= {addr, 1'b0};
state <= DATA;
end
bit_count <= 4'd0;
end
end
end
DATA:
begin
if (scl == 1'b0) begin
bit_count <= bit_count + 1;
if (bit_count == 4'd8) begin
state <= ACK;
bit_count <= 4'd0;
end
end
end
ACK:
begin
if (scl == 1'b0) begin
if (read) begin
state <= START;
bit_count <= 4'd0;
end else begin
state <= STOP;
bit_count <= 4'd0;
end
end
end
NACK:
begin
if (scl == 1'b0) begin
state <= STOP;
bit_count <= 4'd0;
end
end
STOP:
begin
if (scl == 1'b0) begin
scl <= 1'b1;
busy <= 1'b0;
state <= COMPLETE;
end
end
COMPLETE:
begin
if (start) begin
state <= START;
scl <= 1'b0;
shift_reg <= {7'b1111110, 1'b0};
bit_count <= 4'd0;
busy <= 1'b1;
end else begin
state <= IDLE;
end
end
endcase
case (state)
IDLE, START, STOP:
data_out <= 1'b0;
ADDR, DATA:
data_out <= shift_reg[bit_count];
ACK, NACK:
data_out <= 1'b1;
endcase
if (scl == 1'b1 && state == ADDR && bit_count == 4'd7) begin
if (sda == 1'b1) begin
state <= NACK;
end
end
if (scl == 1'b1 && state == DATA && bit_count == 4'd8) begin
if (sda == 1'b1) begin
state <= NACK;
end
end
if (scl == 1'b1 && state == ACK) begin
if (sda == 1'b1) begin
state <= NACK;
end else begin
shift_reg <= {shift_reg[6:0], sda};
bit_count <= bit_count + 1;
end
end
end
end
endmodule
```
在本示例中,我们使用了一个有限状态机来实现 I2C 主机。该状态机有八个状态:IDLE、START、ADDR、DATA、ACK、NACK、STOP 和 COMPLETE。当 start 信号为高时,我们开始一个数据传输。在 IDLE 状态下,busy 信号为低,表示当前没有数据传输。当 start 信号变为高时,我们将 state 状态切换为 START,并且将 busy 信号置为高,表示数据传输已经开始。在 START 状态下,我们将 scl 时钟线拉低,并将 sda 数据线拉低,以发送起始位。在 ADDR 状态下,我们将 addr 地址位放入移位寄存器中。在 DATA 状态下,我们将 data_in 数据位放入移位寄存器中。在 ACK 状态下,我们等待从机发送应答信号。在 NACK 状态下,我们等待从机发送非应答信号。在 STOP 状态下,我们将 scl 时钟线拉高,并将 sda 数据线拉高,以发送停止位。在 COMPLETE 状态下,我们重新回到 IDLE 状态,以准备进行下一个数据传输。
需要注意的是,上述 Verilog 代码示例仅为 I2C 主机的实现。在完整的 I2C 通信系统中,还需要包括从机的实现,以及其他必要的信号和控制逻辑。