Hi All,

I want to add the assert statement in spectre (spectre.scs) file. I have try using following way:


vdd_chk assert sub=INV_1 expr="(V(vdd_ext_por_3v))" min=1.65  max=3.65 message="ERROR: por_vdd is out of range"
vdd_chklimit checklimit checkallasserts=yes enable=["por_vdd_chk"] severity=none
thresold_chk dyn_actnode subckt=INV_1 node=vdd_ext_por_3v dv=1.68  
myopt options dochecklimit=yes save=allpub checklimitdest=file checklimitfile="myfile"



In this way, Simulator will check from 1.65V to 3.65V only. But I want to add some dynamic voltage level. Like, In ramp period after 1.65 V my checkers will consider the given range. So, how to apply in this file?

Right now this checker checks from the initial period (0 ns). I have already know about time frame feature check_windows= [start stop]. But I want to check with voltage level.

So, kindly give me suggestions for dynamic voltage.

I mean, I want to check only voltage level after 1.65. Ignore initial period from zero to voltage ramp start(i.e 1.65V).

Hi Andrew,

I have tried this option. There is no any compilation issue but generated the following warnings. From this warning, I cannot understand the tool is take this option or not. and this option also not dump in waveform.



WARNING (SPECTRE-17003): Assert `vdd_chk' contains an expression that
       needs to be evaluated by MDL. Using this assert frequently may lead to
       performance issues because the MDL evaluator is slower than the native
       assert evaluator.

***************************************
Checklimit Analysis  `vdd_chklimit'
***************************************
The following asserts will be enabled for all subsequent analyses until the
       next checklimit analysis statement is found:
por_vdd_chk : ON

Warning from spectre during transient analysis `transient'.
   WARNING (MDL-351): por_vdd_chk, instance
       sensor_test_top.sip_top_u.chip_top_u.Icore_top.Ianalog_top.I_POR:
       Unable to bind function `cross'.
   WARNING (MDL-1305): Argument 'dir' cannot be cast from 'integer' to
       'name'.
   WARNING (MDL-1306): Argument 'sig' cannot be cast scalar to the waveform.

Hi Andrew,

I have done the simulation successful with assert statement. But, I have a confusion about cross function with rise, fall and both direction.

expr="cross(V(vdd_ext_por_3v),'rise,1,1.65)>0 ? V(vdd_ext_por_3v)

In this statement, rise condition is working fine. But how to use fall and both direction?

I have tried with +1, -1 direction but, it generates following warning and I think, tool is not consider this way.

 WARNING (MDL-351): por_vdd_chk, instance
      sensor_test_top.sip_top_u.chip_top_u.Icore_top.Ianalog_top.I_POR:
      Unable to bind function `cross'.
  WARNING (MDL-1305): Argument 'dir' cannot be cast from 'integer' to
      'name'.
  WARNING (MDL-1306): Argument 'sig' cannot be cast scalar to the waveform.

I'm assuming the question is unrelated to your original question, but more of a question about cross in general - because I presume if it's ramping up, the first crossing would always be in the 'rise direction. All this is doing is trying to check if you've crossed once before applying the limit.

Frank is of course right in pointing out the difference between the MDL function cross and the OCEAN function cross.

Regards,

Andrew

Well, unless you show what the error was when it "shouted" it's rather hard to know. I tried the expression you gave and it worked fine.

In the unlikely event of this being version-specific, knowing the spectre version you're using would be useful too (at the very top of the spectre log file, or what you get from typing "spectre -W" in the terminal window).

Regards,

Andrew.

It's not clear what you want the check to do. Clearly in the fall direction if the threshold is the same as the minimum value of the assert, then the first transition will fail.

Did you perhaps want to do:

clk_chk assert sub=INV_1 expr="cross(V(clk),'fall,1,1.6)>0 ? V(clk ):0.8" min=0.8  max=1.6 message="ERROR: clk is out of range" level=error

This will flag only the first time it goes out of the range 0.8 to 1.6 once it first comes into the range from above 1.6V.

Regards,

Andrew.

As I've said before, it's unclear what you actually want. Maybe you want this:

cross(V(clk),'fall,1,1.6)>0 || cross(V(clk),'rise,1,0.8)>0 || (V(clk)@0 >=0.8 && V(clk)@0 <=1.6) ? V(clk ):0.8

This is untested. What it's saying is if you've crossed from above 1.6 to below 1.6, or you've crossed from below 0.8 to above 0.8, or it was between 0.8 and 1.6 at time 0, then check the voltage on the clock between the min and max range (I only wrote the expression part above).

But I'm guessing...

Andrew.