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时间：10-02 整理：3721RD 点击：

这是一个关于EEPROM的实例，这里是I2C的读写处理程序，请问图中划蓝色线的数字是什么意思?谢谢大神门不吝赐教啊！

源码贴上来吧。感觉代码少了一部分。而且字体看着好奇怪。
大概意思就是C1在“数据写”的模式下。
每一次时钟上升沿C1+1。
当C1计算到100的时候。SDA就变为低电平。
当C1计算到200的时候。SCL就变为低电平。
当C1计算到249的时候，C1就会变为0，同时i加上1.
至于前面的C1等于0的情况应该是SDA和SCL的复位

module iic_com
(
   input CLK,
  input RSTn,

input [1:0] Start_Sig,             //read or write command
input [7:0] Addr_Sig,             //eeprom words address
input [7:0] Wr Data,
output [7:0] Rd Data,
output Done_Sig,

output SCL,
inout SDA
);

parameter F100K = 9'd200;

reg [4:0] i;
reg [4:0] Go;
reg [8:0] C1;
reg [7:0] r Data;
reg r SCL;
reg r SDA;
reg is Ack;
reg is Done;
reg is Out;

assign Done_Sig = is Done;
assign Rd Data = r Data;
assign SCL = r SCL;
assign SDA = is Out ? r SDA : 1'bz;

//****************************************//
//*             I2C 读写处理程序    *//
//****************************************//
always @ ( posedge CLK or negedge RSTn )
if( ！RSTn ) begin
i <= 5'd0;
Go <= 5'd0;
C1 <= 9'd0;
r Data <= 8'd0;
r SCL <= 1'b1;
r SDA <= 1'b1;
is Ack <= 1'b1;
is Done <= 1'b0;
is Out <= 1'b1;
end
else if( Start_Sig[0] )                   //I2C  数据写
   case( i )
   0: // Start
   begin
   is Out <= 1;                         //SDA 端口输出

   if( C1 == 0 ) r SCL <= 1'b1;
   else if( C1 == 200 ) r SCL <= 1'b0;       //SCL 由高变低

   if( C1 == 0 ) r SDA <= 1'b1;
   else if( C1 == 100 ) r SDA <= 1'b0;       //SDA 先由高变低

   if( C1 == 250 -1) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   1: // Write Device Addr
   begin r Data <= {4'b1010, 3'b000, 1'b0}; i <= 5'd7; Go <= i + 1'b1; end

   2: // Wirte Word Addr
reg r SDA;
reg is Ack;
reg is Done;
reg is Out;

assign Done_Sig = is Done;
assign Rd Data = r Data;
assign SCL = r SCL;
assign SDA = is Out ? r SDA : 1'bz;

//****************************************//
//*             I2C 读写处理程序    *//
//****************************************//
always @ ( posedge CLK or negedge RSTn )
if( ！RSTn ) begin
i <= 5'd0;
Go <= 5'd0;
C1 <= 9'd0;
r Data <= 8'd0;
r SCL <= 1'b1;
r SDA <= 1'b1;
is Ack <= 1'b1;
is Done <= 1'b0;
is Out <= 1'b1;
end
else if( Start_Sig[0] )                   //I2C  数据写
   case( i )
   0: // Start
   begin
   is Out <= 1;                         //SDA 端口输出

   if( C1 == 0 ) r SCL <= 1'b1;
   else if( C1 == 200 ) r SCL <= 1'b0;       //SCL 由高变低

   if( C1 == 0 ) r SDA <= 1'b1;
   else if( C1 == 100 ) r SDA <= 1'b0;       //SDA 先由高变低

   if( C1 == 250 -1) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   1: // Write Device Addr
   begin r Data <= {4'b1010, 3'b000, 1'b0}; i <= 5'd7; Go <= i + 1'b1; end

   2: // Wirte Word Addr
else if( C1 == 150 ) r SCL <= 1'b0;

   if( C1 == F100K -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   16:
   if( is Ack ！= 0 ) i <= 5'd0;
   else i <= Go;

      endcase

   else if( Start_Sig[1] )                   //I2C  数据读
   case( i )

   0: // Start
   begin
      is Out <= 1;                      //SDA 端口输出

      if( C1 == 0 ) r SCL <= 1'b1;
      else if( C1 == 200 ) r SCL <= 1'b0;    //SCL 由高变低

   if( C1 == 0 ) r SDA <= 1'b1;
   else if( C1 == 100 ) r SDA <= 1'b0;    //SDA 先由高变低

   if( C1 == 250 -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   1: // Write Device Addr
   begin r Data <= {4'b1010, 3'b000, 1'b0}; i <= 5'd9; Go <= i + 1'b1; end

   2: // Wirte Word Addr
   begin r Data <= Addr_Sig; i <= 5'd9; Go <= i + 1'b1; end

   3: // Start again
   begin
      is Out <= 1'b1;

      if( C1 == 0 ) r SCL <= 1'b0;
   else if( C1 == 50 ) r SCL <= 1'b1;
   else if( C1 == 250 ) r SCL <= 1'b0;

      if( C1 == 0 ) r SDA <= 1'b0;
   else if( C1 == 50 ) r SDA <= 1'b1;
else if( C1 == 150 ) r SDA <= 1'b0;

   if( C1 == 300 -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   4: // Write Device Addr ( Read )
   begin r Data <= {4'b1010, 3'b000, 1'b1}; i <= 5'd9; Go <= i + 1'b1; end

   5: // Read Data
   begin r Data <= 8'd0; i <= 5'd19; Go <= i + 1'b1; end

   6: // Stop
   begin
      is Out <= 1'b1;
      if( C1 == 0 ) r SCL <= 1'b0;
   else if( C1 == 50 ) r SCL <= 1'b1;

   if( C1 == 0 ) r SDA <= 1'b0;
   else if( C1 == 150 ) r SDA <= 1'b1;

   if( C1 == 250 -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   7:                                  //写 I2C  结束
   begin is Done <= 1'b1; i <= i + 1'b1; end

   8:
   begin is Done <= 1'b0; i <= 5'd0; end

   9,10,11,12,13,14,15,16: //发送 Device Addr(write)/Word Addr/Device Addr(read)
   begin
      is Out <= 1'b1;
      r SDA <= r Data[16-i];

      if( C1 == 0 ) r SCL <= 1'b0;
   else if( C1 == 50 ) r SCL <= 1'b1;
   else if( C1 == 150 ) r SCL <= 1'b0;

   if( C1 == F100K -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   17: // waiting for acknowledge
  begin
      is Out <= 1'b0;          //SDA 端口改为输入

      if( C1 == 100 ) is Ack <= SDA;

   if( C1 == 0 ) r SCL <= 1'b0;
   else if( C1 == 50 ) r SCL <= 1'b1;
   else if( C1 == 150 ) r SCL <= 1'b0;

   if( C1 == F100K -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   18:
      if( is Ack ！= 0 ) i <= 5'd0;
   else i <= Go;

   19,20,21,22,23,24,25,26: // Read data
   begin
      is Out <= 1'b0;
      if( C1 == 100 ) r Data[26-i] <= SDA;

   if( C1 == 0 ) r SCL <= 1'b0;
   else if( C1 == 50 ) r SCL <= 1'b1;
   else if( C1 == 150 ) r SCL <= 1'b0;

   if( C1 == F100K -1 ) begin C1 <= 9'd0; i <= i + 1'b1; end
   else C1 <= C1 + 1'b1;
   end

   27: // no acknowledge
   begin
      is Out <= 1'b1;

   if( C1 == 0 ) r SCL <= 1'b0;
   else if( C1 == 50 ) r SCL <= 1'b1;
   else if( C1 == 150 ) r SCL <= 1'b0;

   if( C1 == F100K -1 ) begin C1 <= 9'd0; i <= Go; end
   else C1 <= C1 + 1'b1;
end

endcase

endmodule
这是原码，谢谢你回答我的问题，我主要的疑问是为什么这个C1在200的时候变成电平改变，我能理解这是一个启动写的过程，但是我就有时候纠结在具体数字上。

这个我也不太懂，看看有没有解答吧

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