Library Characterization Tidbits: Define Measurements to Suit Your Characterization Requirements

Hello there,

During memory characterization, if you need to specify custom measurements that are different from the defaults, Liberate MX provides an integrated solution to you. 

Using the define_measure command, you can override the internal methods of Liberate MX or perform measurements that are not directly related to the final characterized .lib file. The process is detailed in the Using Liberate MX define_measure application note that is available on the Cadence Support portal. In this blog, I will summarize the various aspects of defining measurements that are covered in the application note.

Supported command options

The define_measure command supports various options such as, –trig, –targ, –equation, and -failed_value. These allow the users to specify the trigger and target for timing measurements, define the evaluation window, and specify a value to be used for a measurement that fails to evaluate. For a complete list of supported options, you can consult the application note.

Table for define_measure

For Liberate MX to perform the measurements specified using the define_measure command, a proper table file must be provided. The table must include information on arctypes measure, table lines with the necessary trigger event, sufficient time from the triggering event to the end of the transient simulation to accommodate the specified duration, and the events specified by the measurements.

Bundling multiple measurements

There may be times when you need to have multiple define_arc statements for the same arc, maybe because one is required for autoprobing and the other for define_measure, or there may be multiple define_measure commands. In such scenarios, the arc definitions can be tied together using the altos_mx_bundle attribute of the define_arc command.

Debugging the measurements

To understand the measurements made for a define_measure arc, you must analyze the following:

• measure.rpt.fastsim: This file provides a summary of the define_measure equations.
• measure.rpt: This file provides file a summary of the define_measure equations at the partition level.
• mx_debug {measure}: Set this parameter to print information on each valid time interval for measurement evaluation in the log file. 

Excluding measurements from the .lib file

Liberate MX gives you an option to evaluate measurements and exclude those measurements from getting written into the .lib file. For the measurements that you do not want in the .lib file, use define_arc –type measure.

The application note gives detailed insights on the above-mentioned aspects and with some well-explained examples. 

-Jommy Thomas

  

Related Resources

Application Note	Using Liberate MX define_measure
Product Manual	Liberate MX Memory Characterization Reference Manual Liberate Characterization Portfolio Command and Parameter Support Matrix

Contact Us

For any questions, general feedback, or even if you want to suggest a future blog topic, write to liberate_rm@cadence.com. 

About Library Characterization Tidbits

Library Characterization Tidbits is a blog series aimed at providing insight into the useful software and documentation enhancements in the LIBERATE release. In addition, this series would broadcast the voices of different bloggers and experts, who would share their knowledge and experience about all the tools in Liberate Characterization Portfolio. To receive notifications about the new blogs in this series, click Subscribe and submit your email ID in the Subscriptions box.