Stats

  • Locked Locked
  • Replies 4
  • Subscribers 126
  • Views 16620
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

how to set input slew and load in template with Liberate for characterization

fengye

With liberate for characterization, how to set the input slew and load capacitance for the define_template? I mean I want to know the principle of how to properly set these value. I can get a reference from a existing .lib file at 1.2v，but I don't know how to adjust that to re-characterization for 0.6v. I know auto_index can be used, but this is based on the min/max_transition and min output capacitance sepcified by users. I don't konw how to give the proper min/max_transition.
In conclusion,my questions can be concluded as follows:
(1) To re-characterize at the other volatge, how to define proper index_1,2,namely input transition and load for delay and power? How to define index_1,index_2 for sequential cells?
(2) If I choose the auto_index, how I set the min/max transition? I know these setting depends on the behavior and function, but the how to understand the relation and reference.
I need some help, I will appreciate any input from you.

Thanks,
fengye,

Parents
  • Guangjun Cao

    Hi Fengye,

    min_transition is the minimum transition of the cells in your library. max_transition can be defined based on the actual design the library is used for. In other words, you need to know the maximum allowed transition you cells can have in order to meet the design requirement, which is generally the speed of the circuit. min_capacitance can be chose as the minimum input capacitance of of your cells, which do not vary a lot between PVT corners.

    If you want to characterize a new corner, -auto_index will be easier.

    Regards,

    Guangjun 

Reply
  • Guangjun Cao

    Hi Fengye,

    min_transition is the minimum transition of the cells in your library. max_transition can be defined based on the actual design the library is used for. In other words, you need to know the maximum allowed transition you cells can have in order to meet the design requirement, which is generally the speed of the circuit. min_capacitance can be chose as the minimum input capacitance of of your cells, which do not vary a lot between PVT corners.

    If you want to characterize a new corner, -auto_index will be easier.

    Regards,

    Guangjun 

Children
  • fengye
    in reply to Guangjun Cao

    Hi,Guangjun,

    Thanks for your reply! From your answer,  I have such understanding, I can get the  the min_transition from the output port of  my minimum INV cell without capacitance load. For the max_transition, I must consider the speed of the application. Besides, whtether I need to set different delay, power template index for different drive strength cells or not . Besides,  how I  get the index for constrain template? From my observation, the constraint template have three value for each index, which is the min, max,mid of the above delay index. Is that true?

    Regards,

    fengye

  • Guangjun Cao
    in reply to fengye

    Hi Fengye,

    with -auto_index option, Liberate will create index1/2 for all templates, including constraint. This is also based on min/max transition values and size of template, which is defined by users. 

    Regards,

    guangjun

  • fengye
    in reply to Guangjun Cao

    Hi, Guangjun,

    Thanks for your reply! According to what you say, the min/max transition vaule defined by users is really vital. It decides the lookup table for delay,power and constraint. There vaule may influence the correct usage of the library file. So, I guess that a paper or readme file need to explain how to get the proper min/max transition.

    Thanks a lot!

    Regards,

    fengye

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.