module led( input wire sys_clk,//System differential clock 即与顶层不同名字的clk，但还是从顶层导入的 input rst_n,//system reset output led //output led ); parameter MAX=12'd2399; reg [11:0]x; reg [6:0]M; reg [6:0]N; reg a; reg b; initial begin x<=12'd0; M<=7'd0; N<=7'd0; a<=1'b0; b<=1'b0; end always @(posedge sys_clk) begin if(x>=MAX)begin x<=12'd0; if(M>=99)begin M<=7'd0; if(N>=99)begin N<=7'd0; a<=~a; end else begin N<=N+1'd1; end end else begin M<=M+1'd1; end end else begin x<=x+1'd1; end if(M<N&&a==0||M>N&&a==1)begin b<=1; end else begin b<=0; end end assign led=b; endmodule

这是一个 Verilog HDL 语言编写的 LED 控制模块，它包含一个输入时钟信号 sys_clk，一个输入复位信号 rst_n，以及一个输出 LED 灯的信号 led。

该模块使用了 parameter 关键字定义了一个名为 MAX 的参数，值为 12'd2399。在初始状态下，将 x、M、N、a、b 这五个寄存器的值都设为 0。

该模块使用了 always @(posedge sys_clk) begin ... end 的语句块来描述时钟上升沿的行为。当 x 大于等于 MAX 时，将 x 设为 0，并在 M 大于等于 99 时将其设为 0，同时在 N 大于等于 99 时将其设为 0，并且将 a 取反。当 x 小于 MAX 且 M 小于 N 且 a 为 0，或者 x 小于 MAX 且 M 大于 N 且 a 为 1 时，将 b 设为 1，否则将 b 设为 0。

最后使用 assign 关键字将 b 赋值给输出信号 led，从而控制 LED 灯的亮灭。

相关问题

OBUFDS_inst O pin is not connected to a top-level port.

The error message you are seeing indicates that the output pin "O" of an OBUFDS (Differential Output Buffer) instance in your design is not connected to a top-level port.

To fix this error, you need to make sure that the output pin "O" is connected to a top-level port in your design. You can do this by either adding a new top-level port and connecting it to the output pin "O", or by connecting the output pin "O" to an existing top-level port.

Here is an example of how to connect an OBUFDS output pin to a top-level port in Verilog:

module my_design (
  // Top-level ports
  input clk,
  input rst,
  output diff_out_p,
  output diff_out_n
);

  // Instantiate OBUFDS instance
  OBUFDS_inst my_bufds (
    .I(my_input_signal),
    .O(diff_out_p),
    .OB(diff_out_n)
  );

  // Other logic in the module

endmodule

In this example, the output pins "O" and "OB" of the OBUFDS instance are connected to the top-level ports "diff_out_p" and "diff_out_n", respectively. Make sure to replace "my_input_signal" with the signal you want to buffer.