Hi Nishant,

cross statements are used to enusure the simulator does not miss the all important events, like for your example positive edge of a clock. You may need to add tighter tolerances sometimes so that a numerical simulator like spectre doesnt miss it.

So, if you do not want to use cross, then you are taking a risk and your model is becoming less robust!!

But from my own experience sometimes you can remove some of the cross statements if you are sure that the simulator is anyway going to take time steps small enough to NOT miss the event.

I can suggest 3 ways:

1. For your clock example, consider clk is the signal name, and th = (vdd+vss)/2, be the threshold.
Then,....

analog begin
  clk_prev = clk_current;   // 2 real variables, storing the vakues of the clock signal in time tn and                                   // tn+1. Imagine what will happen if the gap between tn and tn+1 are not small enuf!!!
  clk_current = V(clk);
  if(clk_current > th && clk_prev < th)
               you have a positive edge of clock

  if(clk_current < th && clk_prev > th)
              you have a negative edge of clock
end

This works if your clock is an input and the simulator is not missing the clock edges. This might sound a bit confusing  ::) Actually it means the gap between tn and tn+1 (mentioned above) are small enough.

2. Relax the tolerances in your  cross statements.
3. Use bound_step or use max_step in your transient analysis.

Hope it helps!
Rajdeep