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In the following code, I am storing the history of buttons player 1 and player 2 pressed. The code compiles without errors but has warnings. I am unable to solve these warnings. I am posting the code here.

module game(clk50,red,green,blue,hsync,vsync, button,led);

input [8:0] button;
 input clk50;
 output  red;
 output  green;
 output  blue,led;
 output hsync;
 output vsync;
 // divide input clock by two, and use a global 
// clock buffer for the derived clock
reg clk25_int;
always @(posedge clk50) begin
clk25_int <= ~clk25_int;
end
wire clk25;
BUFG bufg_inst(clk25, clk25_int);
wire [9:0] xpos;
wire [9:0] ypos;

Grid_Display Grid_Displayinst(clk25,xpos, ypos, red, green, blue, button,led);

endmodule

module Grid_Display(clk25,xpos,ypos,red,green,blue, button,led);

 input clk25;
 input [9:0] xpos;//responsible for current pixel display location
 input [9:0] ypos;// responsible for current display row

 input [8:0] button;

 //spartan 3 kit has 3-bits per pixel, so 2^3 means 8 colours can be selected.

 output red; // colour 1
 output green; // colour 2
 output blue; // colur 3
 output led;

 //reg tempRed,tempGreen,tempBlue, GridRed,GridGreen,GridBlue;

 reg player1,player2;

 reg [8:0] player1History=0,player2History=0;


 wire grid = ((xpos >= 4 && xpos <= 799 &&  ypos >= 160 && ypos <= 165) || 
              (xpos >= 4 && xpos <= 790 &&  ypos >= 310 && ypos <= 315) ||
              (xpos >= 200 && xpos <= 205 &&  ypos >= 0 && ypos <= 520) || 
              (xpos >= 440 && xpos <= 445 &&  ypos >= 0 && ypos <= 520));



always @(posedge clk25)
begin

  player1History=  button ^ player2History;
  player2History=  button ^ player1History;

  player1 = ((player1History[0] && (xpos >=50 && xpos<=150 && ypos >= 20 && ypos <=120) ) || (player1History[1] && (xpos >=250 && xpos<=350 && ypos >= 20 && ypos <=120))
          || (player1History[2] && (xpos >=490 && xpos<=590 && ypos >= 20 && ypos <=120)) || (player1History[3] && (xpos >=50 && xpos<=150 && ypos >= 180 && ypos  <=280))
          || (player1History[4] && (xpos >=250 && xpos<=350 && ypos >= 180 && ypos <=280)) || (player1History[5] && (xpos >=490 && xpos<=590 && ypos >= 180 && ypos <=280))
          || (player1History[6] && (xpos >=50 && xpos<=150 && ypos >= 330 && ypos <=430)) || (player1History[7] && (xpos >=250 && xpos<=350 && ypos >= 330 && ypos <=430))
          || (player1History[8] && (xpos >=490 && xpos<=590 && ypos >= 330 && ypos <=430)));

  player2 = ((player2History[0] && (xpos >=50 && xpos<=150 && ypos >= 20 && ypos <=120) ) || (player2History[1] && (xpos >=250 && xpos<=350 && ypos >= 20 && ypos <=120))
          || (player2History[2] && (xpos >=490 && xpos<=590 && ypos >= 20 && ypos <=120)) || (player2History[3] && (xpos >=50 && xpos<=150 && ypos >= 180 && ypos <=280))
          || (player2History[4] && (xpos >=250 && xpos<=350 && ypos >= 180 && ypos <=280)) || (player2History[5] && (xpos >=490 && xpos<=590 && ypos >= 180 && ypos <=280))
          || (player2History[6] && (xpos >=50 && xpos<=150 && ypos >= 330 && ypos <=430)) || (player2History[7] && (xpos >=250 && xpos<=350 && ypos >= 330 && ypos <=430))
          || (player2History[8] && (xpos >=490 && xpos<=590 && ypos >= 330 && ypos <=430)));

end 

 assign red = (grid || player1 );
 assign green = (grid || player2);
 assign blue = (grid );

endmodule

How can I solve these warnings?

WARNING:Xst:2211 - "grid.v" line 104: Instantiating black box module <dummyModule>.
WARNING:Xst:1710 - FF/Latch <player2> (without init value) has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_0> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_1> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_2> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_3> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_4> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_5> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_6> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_7> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:1896 - Due to other FF/Latch trimming, FF/Latch <player2History_8> has a constant value of 0 in block <Grid_Display>. This FF/Latch will be trimmed during the optimization process.
WARNING:Xst:2036 - Inserting OBUF on port <led> driven by black box <dummyModule>. Possible simulation mismatch.

Regards

4

1 回答 1

5

所有关于 FF/Latch 修剪的警告基本上都归结为 player2History 始终为 0 的问题，因此它正在被优化。

它看起来不应该总是 0，但事实证明它是正确的，因为您使用了错误类型的阻塞语句这一事实的有趣副作用。

问题在于您的 always 块中的这两行：

always @(posedge clk25) begin
 player1History=  button ^ player2History;
 player2History=  button ^ player1History;

然后，您的逻辑评估如下：

  1. 在开始时间 player2History (p2h) 为零。
  2. 在时钟的某个姿势上，假设按钮非零。此时 p2h 仍然为零，所以p1h = button ^ 0只是意味着 p1h 被分配了 button 的值。
  3. 现在下一个语句被评估，你正在评估button ^ p1h，但由于我们刚刚分配p1h = button，你真的在​​评估button ^ button，我们知道它总是 0。
  4. 由于在这种情况下 p2h 不可能为非零，因此从您的设计中删除了触发器。

您可能打算做的是使用运算符进行 p1h 和 p2h非阻塞分配<=。当您使用非阻塞时，这意味着两个语句都是并行计算的，因此 p1h 和 p2h 都根据它们的旧值进行计算，而不是先计算第一行，然后在第二行中使用这个结果。

理解阻塞和非阻塞语句之间的区别在verilog中非常重要，如果你不理解这个概念或者什么时候使用它们，那么你应该寻求额外的培训材料。

于 2013-05-15T07:48:01.113 回答