Cadence Liberate Characterization Help

Hi Anuradha,

I am also trying to generate .lib files using the Liberate tool. Since you have already gone through the process, can you please help me with one issue?
I have created a netlist from my circuit and used it in liberate to generate .lib file. However, it seems like the generated netlist is not compatible with the liberate or maybe be I am missing something. Have you had a this kind of issue?

Thanks in advance.

Best regards.
Hossain

Hi, can you be more specific about the issue you have ? Does Liberate give errors when reading the netlist ? 

Anuradha

Hi Anuradha,

Thank you for your reply and I am sorry for my late response.

I have tried with the sample run script, model file, and template provided with the Liberate tool and got the library creation working (shown in figure working_lib.png).
However, when I tried with an extracted inverter netlist (attached inv_netlist_extracted.png) and 45nm NCSU PDK, the generated output is showing the cell_leakage_power as 0. In addition, the library that I have generated is not showing the inverter functionality like the other one (working_lib.png) is showing.

I have attached the run script and template I am using. In addition, I have attached the working and incorrect generated library.

Can you please take a look and see what might causes this issue?

Thank you for your time.

Best regards,

Hossain

Hi Hossain,

Did your characterisation run finish successfully? please check the logfile for any warning or errors. do you see INVX1 in the 'List of failing cells' at the end of your logfile? 

For further debug, please use the following settings to save the spice decks and run standalone Spectre to check the simulation results.

set_var extsim_deck_dir  <full_path_here>

set_var extsim_save_passed deck

set_var extsim_save_failed deck

Regards,

Guangjun

Hi Cao,

I am not getting any error and characterization was finished successfully. None of the cells are listed in 'List of failing cells'.
I have made the changes as you suggested but I am still seeing the "cell_leakage_power: 0" and "function: 0". 
Can you please suggest anything else that might solve this issue?

By the way, there are couple of folders generated in the spice deck. What is the proper way of debugging if there is any error?

Thank you for your time and help.

Best regards,
Hossain.

Hi Cao,

I am not getting any error and characterization was finished successfully. None of the cells are listed in 'List of failing cells'.
I have made the changes as you suggested but I am still seeing the "cell_leakage_power: 0" and "function: 0". 
Can you please suggest anything else that might solve this issue?

By the way, there are couple of folders generated in the spice deck. What is the proper way of debugging if there is any error?

Thank you for your time and help.

Best regards,
Hossain.

under the directory you specified with extsim_deck_dir, there are compressed files for each cell. unpack the corresponding tarball. you will see a map.lst file, which describes the mapping of arcs and directories. in each leaf directory, there is a sim.sp. open the file and remove save/nosave option. save a file and run spectre on this file. after the run, using Viva to view the waveform. For leakage, you need to refer to Liberate documentation on how leakage is calculated.

With the char_library command option, you do not need any define_leakage or define_arc commands.

there is also an example directory in liberate installation directory, which can be used as reference.

Good luck.

Guangjun 

Hi, Cao is right ! char_library automatically calculates leakage if not specifically written. 

Anuradha

I can not find out the reason with what you have provided. It could be some problems with your input data or the settings. Also, please try -extsim spectre option in your char_library command.  

If you need further help, please submit a Case, and provide a test case with the run results as they are. 

Regards,

Guangjun

Hi Cao,

I have used -extsim spectre option, but still having the same issue; its not generating the leakage power.
Unfortunately I don't have the access to submit a case. I think as an academic user I only have access to online support database. I will keep trying to see if I can fix this issue.
Thank you for your help and time.

Best regards,

Hossain

can you show me the full logfile?

Hi Cao,

Sure. The log file is included in this (http://ge.tt/9DDpc4s2) link.

Thank you.

Best regards,
Hossain

You are using a very old Liberate release. Please download the latest release first.

There are many warnings in your logfile. The most critical one might be during netlist parsing, "Warning from parser during circuit read-in...". These warnings could mean no devices are recognized correctly.

After "generating vectors...", you should see timing related information, in addition to power/leakage. But they do not exist. 

So, the most possible issue is in your netlist and/or model files.

regards,

Guangjun

"/home/DREXEL/msh89/ECEC574/ecect680-s2017/LIBERATE_EXAMPLE/MODELS/include_SS.sp", line 7: Warning: Possible reason is that no section is specified when using statement .lib "
From this message, it looks like you did not specify a corner section here.

INFO (LIB-926): The definition of the sub-circuit or model for instance 'MM_i_1' could not be found. Run the following checks in the given sequence: the subcircuit or model is loaded, the first line in the model file is empty or has a comment, and the netlist syntax is correct. If no problem is found in these checks, use the 'define_leafcell' command to define the sub-circuit or model, and rerun Tcl.

This message indicates you may have to use define_leafcell command to declare model for MM_i_1. This is typically required when you use exclusive_model_included and "char -extsim".  

Hi Guangjun,

Out of the curiosity I am asking, I know that "define_arc" command is not mandatory. But in Liberate example folder, the template used for re-characterization of the library (template_rechar_example.tcl) has defined several power/delay arcs for both sequential and combinatorial cells. Is it specifically done to shorten the .lib file content ? 

Let's say for a simple dynamic double edge-triggerd flip-flop (shown below), is automatic arc determination by Liberate  (without define_arc) enough for accurate results ? 

Thanks