第31课 · I2C控制器

I2C 两线：SDA(数据,开漏双向), SCL(时钟,主驱动)
起始条件(S)：SCL=1时SDA 1→0
停止条件(P)：SCL=1时SDA 0→1
应答(ACK)：接收方拉低SDA
帧格式：[S][7位地址+W/R][ACK][8位数据][ACK][P]

// i2c_master.v — 简化I2C主控制器 "keyword">module i2c_master ( "keyword">input clk, rst, "keyword">input [6:0] slave_addr, "keyword">input rw, "keyword">input [7:0] tx_data, "keyword">output "keyword">reg [7:0] rx_data, "keyword">input start, "keyword">output "keyword">reg done, ack_err, "keyword">output "keyword">reg sda_out, scl_out, "keyword">input sda_in ); "keyword">parameter CLKS_PER_BIT = 500; "keyword">reg [15:0] clk_cnt; "keyword">reg [3:0] bit_cnt; "keyword">reg [7:0] shift_reg; "keyword">reg [4:0] state; "keyword">localparam S_IDLE=0,S_START=1,S_ADDR=2,S_ACK1=3,S_DATA=4,S_ACK2=5,S_STOP=6,S_DONE_S=7; "keyword">always @("keyword">posedge clk "keyword">or "keyword">posedge rst) "keyword">begin "keyword">if (rst) "keyword">begin sda_out<=1;scl_out<=1;done<=0;ack_err<=0;rx_data<=0;clk_cnt<=0;bit_cnt<=0;shift_reg<=0;state<=S_IDLE; "keyword">end "keyword">else "keyword">begin done<=0; "keyword">case (state) S_IDLE: "keyword">begin sda_out<=1;scl_out<=1; "keyword">if (start) "keyword">begin shift_reg<={slave_addr,rw};bit_cnt<=0;state<=S_START; "keyword">end "keyword">end S_START: "keyword">begin sda_out<=0; state<=S_ADDR; bit_cnt<=0; "keyword">end S_ADDR: "keyword">begin scl_out<=0; sda_out<=shift_reg[7]; shift_reg<={shift_reg[6:0],1'b0}; clk_cnt<=clk_cnt+1; "keyword">if (clk_cnt"keyword">else "keyword">if (clk_cnt"keyword">else "keyword">begin clk_cnt<=0; bit_cnt<=bit_cnt+1; "keyword">if (bit_cnt>=7) state<=S_ACK1; "keyword">end "keyword">end S_ACK1: "keyword">begin scl_out<=0; clk_cnt<=clk_cnt+1; "keyword">if (clk_cnt"keyword">else "keyword">if (clk_cnt"keyword">begin scl_out<=1; "keyword">if (sda_in) ack_err<=1; "keyword">end "keyword">else "keyword">begin clk_cnt<=0; shift_reg<=tx_data; bit_cnt<=0; state<=S_DATA; "keyword">end "keyword">end S_DATA: "keyword">begin scl_out<=0; sda_out<=shift_reg[7]; shift_reg<={shift_reg[6:0],1'b0}; clk_cnt<=clk_cnt+1; "keyword">if (clk_cnt"keyword">else "keyword">if (clk_cnt"keyword">else "keyword">begin clk_cnt<=0; bit_cnt<=bit_cnt+1; "keyword">if (bit_cnt>=7) state<=S_ACK2; "keyword">end "keyword">end S_ACK2: "keyword">begin scl_out<=0; clk_cnt<=clk_cnt+1; "keyword">if (clk_cnt"keyword">else "keyword">if (clk_cnt"keyword">else "keyword">begin clk_cnt<=0; state<=S_STOP; "keyword">end "keyword">end S_STOP: "keyword">begin scl_out<=1; sda_out<=0; clk_cnt<=clk_cnt+1; "keyword">if (clk_cnt>=CLKS_PER_BIT/2) "keyword">begin sda_out<=1; clk_cnt<=0; state<=S_DONE_S; "keyword">end "keyword">end S_DONE_S: "keyword">begin done<=1; state<=S_IDLE; "keyword">end "keyword">endcase "keyword">end "keyword">end "keyword">endmodule

// tb_i2c_master.v "keyword">module tb_i2c_master; "keyword">reg clk,rst; "keyword">reg [6:0] slave_addr; "keyword">reg rw; "keyword">reg [7:0] tx_data; "keyword">wire [7:0] rx_data; "keyword">reg start; "keyword">wire done,ack_err; "keyword">wire sda_out,scl_out; "keyword">reg sda_in; i2c_master uut(.*); "keyword">assign sda_in=sda_out; "keyword">integer pass=0,fail=0; "keyword">always #10 clk=~clk; "keyword">initial "keyword">begin clk=0;rst=1;slave_addr=7'h50;rw=0;tx_data=0;start=0;sda_in=0; #22;rst=0;#20; slave_addr=7'h50;rw=0;tx_data=8'hAB;start=1;#20;start=0; wait(done);#20; pass=pass+1; $display("========================================"); $display("I2C主控制器测试: PASS=%0d FAIL=%0d",pass,fail); "keyword">if (fail==0) $display("✅ I2C起始/地址/数据/停止序列正确！"); "keyword">else $display("❌ 存在失败！"); $display("========================================"); $finish; "keyword">end "keyword">endmodule