Design of Feedback Oscillator:

The feedback oscillator which is going to be designed as shown below.

Case-1: using NBA

always@(posedge clk, negedge rst) begin

  if (rst) a <= 0;

  else a <= b;

end

always@(posedge clk, negedge rst) begin

  if (rst) b <= 1;

  else b <= a;

end

Here always blocks are executed in any order, when reset = 1 then a = 0,b = 1 and when reset is released then a = 1, b = 0.In next posedge the values of a and b are interchanged and this process continuous until the end of simulation.

Case-2: using BA

always@(posedge clk, negedge rst) begin

  if (rst) a = 0;

  else a = b;

end

always@(posedge clk, negedge rst) begin

  if (rst) b = 1;

  else b = a;

end

Here the values of a and b depends on the order of execution of always blocks i.e., Race condition.