Divide by 2 clock and corresponding reset generation

Question

My question is about using generate a synthesizable divide by 2 clock and corresponding reset in verilog.

We can generate a divide by 2 clock as below using verilog

module frquency_divider_by2(
  input      rst_n,
  input      clk_rx,
  output reg clk_tx
);

always @ (posedge clk_rx) begin
  if (~rst_n) begin
    clk_tx <= 1'b0;
  end
  else begin
    clk_tx <= ~clk_tx;
  end
end

endmodule

My question is how to generate corresponding reset(to be used by flops using clk_tx) using rst_n

Can any one help me for the same.

I appreciate your help

Answer 1

To async apply the reset and release after two positive edges of clk_tx. Waiting 2 positive edges stops the reset from being low for fractions of a clock period.

output reg rst2_n;
reg temp;

always @ (posedge clk_rx, negedge rst_n ) begin
  if (~rst_n) begin
    {rst2_n,temp} <= 2'b0;
  end
  else begin
   {rst2_n,temp} <= {temp, 1'b1};
  end
end

For a synchronous reset you would need to check if it was low for any section of the faster clock, during synthesis you would need to check the cdc (clock domain crossing).

output reg rst2_n;
reg [1:0] sync_reset_n;
always @ (posedge clk_rx) begin
  sync_reset_n[1:0] <= {sync_reset_n[0], rst_n};
  rst2_n            <= &sync_reset_n ; //AND BIT reduction
end