Hello, while working with a design, I am facing zero time loop in VCS. One of my state machine is causing this zero delay loop and after spending some time, looks like the following snippet of code are responsible for this.
// .... state register code
// always(*) for next state and output logic
case (state)
state0: begin
if (start_i == 1) begin
temp = 8'd117;
next_state = state1;
end else begin
next_state = state0;
end
end
state1: begin
if (end_i != 1) begin
temp = temp + data_i; // *** looks like something is wrong here. If i remove it then VCS doesn't stuck in zero time loop
if (temp >= 9'd256) begin
temp = temp - 9'd256;
end
next_state = state2;
end else begin
next_state = state3;
end
end
As you can guess, in each cycle after having start_i == 1 I add input 8 bit data_i with temp and keep doing it.... I know without looking at the full design its hard to tell but I would appreciate if someone can point me to any error/buggy coding style from above code snippet which might be responsible for the error.
