I'm trying to generate IBIS models for the parts that I'm designing.  I'm designing using CADENCE Virtuoso.  

I'm wondering if there is a tutorial for generating IBIS models in CADENCE Virtuoso.   Please pardon me if my question is broad.      

Those who work in the IC Packaging design space have some unique challenges. We bridge between the IC design world (90/45-degree traces with rectangular and octagonal pins) and the PCB domain...

[[ Click on the title to access the full blog on the Cadence Community site. ]]

In this week’s Whiteboard Wednesdays video, Dave Apte discusses how to create the lowest power design possible by using architectural exploration and Cadence’s Stratus HLS solution....

[[ Click on the title to access the full blog on the Cadence Community site. ]]

The 2019 HF1 production release for Clarity, Celsius, and Sigrity Tools is now available for download at Cadence Downloads . SIGRITY2019 HF1 For information about supported platforms, compatibility...

[[ Click on the title to access the full blog on the Cadence Community site. ]]

Everyone keeps talking about “the cloud” this and “the cloud” that these days—but you’re a semiconductor designer. Everyone keeps saying “the cloud” is revolutionizing all aspects of electronics design—but what does it mean for you? Cadence's own Tom Hackett discussed this in a presentation at the Cadence Theater during DAC 2019.

What people refer to as “the cloud” is commonly divided into three categories: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and software as a Service (SaaS). With IaaS, you bring your own software—i.e. loading your owned or appropriately licensed tools onto cloud hardware that you rent by the minute. This service is available from providers like Google Cloud Platform, Amazon Web Service, and Microsoft Azure. In PaaS (also available from the major cloud providers), you create your own offering using capabilities and a software design environment provided by the cloud vendor that makes subsequent scaling and distribution really easy because the service was “born in the cloud”.  Lastly, there’s SaaS, where the cloud is used to access and manage functionality and data without requiring users to set up or manage any of the underlying infrastructure used to provide it.  SaaS companies like Workday and Salesforce deliver their value in this manner.  The Cadence Cloud portfolio makes use of both IaaS and SaaS, depending on the customers’ interest.  Cadence doesn’t have PaaS offerings because our customers don’t create their own EDA software from building blocks that Cadence provides.

All of these designations are great, but you’re a semiconductor designer. Presumably you use Workday or some similar software, or have in the past when you were an intern, but what about all of your tools? Those aren’t on the cloud.

Wait—actually, they are.

Using EDA tools in the cloud allows you to address complexity and data explosion issues you would have to simply struggle through before. Since you don’t have to worry about having the compute-power on-site, you can use way more power than you could before. You may be wary about this new generation of cloud-based tools, but don’t worry: the old rules of cloud computing no longer apply. Cloud capacity is far larger than it used to be, and it’s more secure. Updates to scheduling software means that resource competition isn’t as big of a deal anymore. Clouds today have nearly unlimited capacity—they’re so large that you don’t ever need to worry about running out of space.

The vast increase in raw compute available to designers through the cloud makes something like automotive functional safety verification, previously an extremely long verification task, doable in a reasonable time frame. With the cloud, it’s easy to scale the amount of compute you’re using to fit your task—whether it’s an automotive functional safety-related design or a small one.

Nowadays, the Cadence Cloud Portfolio brings you the best and brightest in cloud technology. No matter what your use case is, the Cadence Cloud Portfolio has a solution that works for you. You can even access the Palladium Cloud, allowing you to try out the benefits of an accelerator without having to buy one.

Cloud computing is the future of EDA. See the future here.

All PCB designers know the importance of proper power delivery for successful board design. Integrated circuits need the power to turn on, and ICs with marginal power delivery will not operate reliably. Since power planes can...(read more)

If you weren't able to attend the 2013 DVCon, you missed out on a great IEEE 1801/UPF tutorial delivered by members of the IEEE committee. Accellera had the event recorded and that recording is now posted on the Accellera.org website. Regardless of your work so far with low power design and verification, you need to watch this video.

Power management is becoming ubiquitous in our world. The popular aspect is that reduced power is good for the evironment and that is true. But for those teams that have been building chips around the 40nm node and below, there is another truth. Power management is required simply to get working silicon in many cases. As the industry expands the number of designs with power management and forges deeper into advanced nodes, we steadily identify improvements to the power format descriptions. The most recent set of imporvements to the IEEE 1801 standard are now available in the 2013 version of that standard.

To help bring the standard to life, five representatives from the IEEE joined to deliver a tutorial at DVCon in 2013. Qi Wang (Cadence), Erich Marschner (Mentor), Jeffrey Lee (Synopsys), John Biggs (ARM), and Sushma Honnavarra-Prasad (Broadcom) each contributed to the tutorial. It started with a review of the UPF basics that led to the IEEE 1801 standard delivered by the EDA companies. The IEEE 1801 users then presented tutorial content on how to apply the standard. The session then concluded with a look forward to the IEEE 1801-2013 (UPF 2.1) standard. The standard was released two months after the DVCon tutorial and is available through the Accellera Get program.

So after the bowl games are over and you'vre returned through the woods and back over the river from Grandma's, grab a cup of hot cocoa and learn more about the power standards you may well be using in 2014.

Regards,

Adam "The Jouler" Sherer

ST Microelectronics reported their success with IEEE 1801 / UPF low-power simulation using Incisive Enterprise Simulator at CDNLive India in November 2013. We were able to meet with Mohit Jain just after his presentation and recorded this video that explains the key points in his paper.

With eight years of experience and pioneering technology in native low-power simulation, Mohit was able to apply Incisive Enterprise Simulator to a low-power demonstrator in preparation for use with a production set-top box chip.  Mohit was impressed with the ease in which he was able to reuse his existing IEEE 1801 / UPF code successfully, including the power format files and the macro models coded in his Liberty files. Mohit also discusses how he used the power-aware Cadence SimVision debugger.

The Cadence low-power verification solution for IEEE 1801 / UPF also incorporates the patent-pending Power Supply Network visualization in the SimVision debugger.  You can learn more about that in the Incisive low-power verification Rapid Adoption Kit for IEEE 1801 / UPF here in Cadence Online Support.

Just another happy Cadence low-power verification user!

Regards,

 Adam "The Jouler" Sherer 

Hello,

I am using virtuoso version IC 6.1.7-64b.500.1, and I am trying to follow the Spectre RF Workshop-Noise-Aware PLL Design Flow(MMSIM 7.1.1) pdf.

I could find the workshop library "pllMMLib", but I cannot find PLL Macro Model Wizard, and I attached my screen.

Could you please help me install the module "PLL Macro Model Wizard"?

Thanks a lot!

Hi experts,

I have a problem with my design as below

ERROR: in SHAPE (-2.3622 2.3622)

  class = ETCH

  subclass = TOP 

  Part of Symbol Def SHAPE_4725X4725.

      Which is part of a padstack as a SHAPE symbol.

  ERROR(SPMHDB-187): SHAPE boundary may not cross itself.

   Error cannot be fixed.

       Object has first point location at (-2.3622 2.3622).

Can you tell me how to solve my problem?

Thanks a lot.

I'm working on a circuit that requires the input voltage to be converted to a frequency, transmitted over an optical cable, and then converted back to a voltage. I am attempting to simulate this circuit using Eagle ngSpice simulations. The voltage to frequency converters that I am using are ADVFC32 and made by Analog Devices. However, I can't seem to find a SPICE model for this component. Analog Devices does not provide it on their website. Can anyone find a SPICE Model for this part? I'm new to working with electronics so any help/advice you can provide would be appreciated.

Hello, i am a student who is studying Allegro tool with SKILL.

I have a question about SKILL axlSegDelayAndZ0. The reference says this function "returns the delay and impedance of a cline segment."

I want to know how many components does this tool consider when calculating timing delay from the length. 

How steep is input signal's rise transition? Is rise transition shape isosceles trapezoid or differential increasing shape?

Also, if it is a multi fan-out, the rise transition time will be different net by net. How can this tool can calculate in this case?

I want to hear answers about these questions.

Thank you for reading this long boring questions, and i will be waiting for answers.

Hi,

I have to Take DRC report by cadence skill code I don't know the command to get Element 1 and Element 2 Report any one please help me out.

I am working on some SKILL scripts which are loaded by allegro.ilinit at startup.

If I edit my .il-files how do I get them updated in Allegro?

Right now I restart the program but there must be a simpler way.

A newbie question, I know...  

Hi All,

I'm trying to understand checkpoint concept. When I found save and restart concept in cdnshelp, There is just describing about "$save" and "xrun -r "~~~".

and I found also the below link about save restart and it saves your time.

But I can't find any benefits from my experiment from save&restart article( I fully agree..the article)

Ok, So I'v got some experiment  Here.

1. I declared $save and got the below result as I expected within the simple UVM code.

In UVM code...

$display("TEST1");
$display("TEST2");
$save("SAVE_TEST");
$display("TEST3");
$display("TEST4");

And I restart at "SAVE_TEST" point by xrun -r "SAVE_TEST", I've got the below log

xcelium> run
TEST3
TEST4

Ok, It's Good what I expected.(The concept of Save and Restore is simple: instead of re-initializing your simulation every time you want to run a test, only initialize it once. Then you can save the simulation as a “snapshot” and re-run it from that point to avoid hours of initialization times. It used to be inconvenient. I agree..)

2. But The Problem is that I can't restart with modified code. Let's see the below example.

I just modified TEST5 instead of "TEST3"

$display("TEST1");
$display("TEST2");
$save("SAVE_TEST");
$display("TEST5"); //$display("TEST3");
$display("TEST4");

and I rerun with xrun -r "SAVE_TEST", then I've got the same log

xcelium> run
TEST3
TEST4

There is no "TEST5". Actually I expected "TEST5" in the log.From here We know $save can't support partially modified code after $save. 

Actually, through this, we can approach to our goal about saving developing time. 

So I want to know Is there any possible way that instead of re-initializing our simulation every time we want to run a test, only initialize it once and keep developing(debugging) our code ?

If we do, Could you let me know the simple example?

Hi all,

I need to develop a digital design/verification solution to compile,elaborate and simulate SV designs (basically a complex xrun wrapper). I am an experienced user of xrun and I have done a number of these wrappers over the years but this one is to be more of a tool, intented to be used Company-wise, so it needs to be very well thought and engineered.

It needs to be robust, simple and extensible. It needs to support multi-snapshot elaboration, run regressions on machine farms, collect coverage, create reports, etc.

I've been browsing the vast amount of documentation on XCELIUM and, although very good, I can't find any document which puts together all the pieces of what I am trying to achieve. I suppose I am more clear on the elaboration, compilation and simulation part but I am really lacking on the other areas like : LSF, regressions coverage, where does vManager fits in all this, etc.

I'd appreciate if someone can comment on whether there is a document which depicts how such a DV flow can be put together from scratch, or whether there is a kind of RAK with some example xrun wrapper.

Thanks

Hi

     I want develope basic circuit of DC motor which consist of resistor, inductor and back emf in capture and check its simulation in pspice, for reference I have attached image and link.

https://www.precisionmicrodrives.com/content/ab-025-using-spice-to-model-dc-motors/ .

Hi All,

I want to capture the transition values of certain nodes in a design (i.e. a digital multiplier built with standard cells) and I use probe -screen command to dump the nodal values in text format. Since I only need to capture these values in the ideal situation, I use -nospecify switch with the xrun command :

xrun -clean R16FA_2009.v R4BE_Test.v tb_stop16.v -v stdlib_verilog_models-sdf30.v -access +rwc -mess -timescale 1ns/1ps -nospecify -gui &

and the probe command goes like this : 

probe -screen tb_stop16.mul16.test.L1 -redirect probe1.txt -format "%T L1 Value: %b"  //Here L1 is an array of wires

Although I expect a single transition at a given time instance, I see multiple transitions occurring in the dumped probe1.txt file. i.e. 

Time: 300 PS : 48'bxx0xx0xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx0xx0xx11x
Time: 300 PS : 48'b000000000000000000000000000000000000000000000110
Time: 4 NS : 48'b001000000000000000000000000000000000000000000100
Time: 4 NS : 48'b011000000010111111111001000000110011011001010101
Time: 8 NS : 48'b010000000010111111111001000000110011011001010101
Time: 8 NS : 48'b110100101100000110000111100001010010111001011100
Time: 12 NS : 48'b010000110011100010001110011100010101010001010101
Time: 16 NS : 48'b000010000010000000000000000010000000010010010100
Time: 20 NS : 48'b000011000010000000000000000010000000010010010100
Time: 20 NS : 48'b000001001001001001011011000010001010011010010100

From the waveform, it appears that only the second value (bold)  of the time instance is correct. Since the simulation is without annotated delays, there are no intermediate transitions in the waveform. How could this be possible ?

Thanks in advance

Hello folks,

Greetings.

One of my customer claims that he is using Cadence IES version 18.09.011 with Vivado 2019.2. The version of IES that we officially support with Vivado 2019.2 is 15.20.073. Though the tool is forward compatible, I am not sure what are the versions of IES that are released after 15.20.073. Could you please give me a list of the versions of Cadence IES released after 15.20.073 and which is the latest version as of now ?

Best regards,

Chinmay

Hi,

I am facing this elaboration error when using Xcelium:

Command>

    xmverilog -v200x +access+r +xm64bit -f vlist -reflib plib -timescale 1ns/1ps

Log>

    xmelab: *E,CUVMUR (<name>.v,538|18): instance 'LUTP0.C GLAT3' of design unit 'tlatntscad12' is unresolved in 'worklib.LUTP0:v'.

I guess the plib was not referred to as the simulation configuration because the tlatntscad12 is included in plib.

The plib is compiled by INCISIVE 13.20 and I am using the Xcelium 19.30.

Please tell me the correct command on how to refer to the library directory compiled by different versions.

Thank you,

I am importing sessions which are run by other people to analyse and I would like to remove them from my vManager Regressions tab as they become obsolete. As I am not the original person who run the sims, I cannot "delete" sessions. What are my options? Thanks.

hi,

due to technical problem i am running simulation through terminal. Therefore, I have a Verilog file, a test bench and i have also exported from Genus synthesized netlist and sdf file. Now, how can i annotate sdf in my post-synthesis simulation using XCELIUM while using command line?

thank you

  A few weeks ago, we talked about template text labels for design-specific information. There, we were focused on labels that are specific to the design as a whole: revision information, dates, authors, etc. Today, we’re looking at a diff...(read more)

No, this isn’t a Hollywood movie. We’re talking about pieces of plane shapes with no connections to them, not an idyllic private oasis in the Caribbean (sorry). Removing shape islands is something you’ve always been able to do in th...(read more)

In the Allegro back-end layout products like Allegro Package Designer Plus, it would be reasonable to assume that the most often used command is none other than “show element” (shortcut key F4). This command, runnable at nearly any t...(read more)

Those who work in the IC Packaging design space have some unique challenges. We bridge between the IC design world (90/45-degree traces with rectangular and octagonal pins) and the PCB domain (any-angle routing, filled planes, and a multitude of pad ...(read more)

Greeting to all:

I am new in this tool, only 2 weeks. Trying to create a new Via with smaller size drill hole from exiting 13 mils size to 10 mils size. I got the message as imaged below. Any advise what to do?  Thanks in advance.

I would like to add these components to the component bank in ORCAD simulation. Even an accessible or free course that explained how to create these components.

Please include a brief summary of how to use it.

As noted in white papers, posts on the Team Specman Blog, and the Specman documentation, IntelliGen is a totally new stimulus generator than the original "Pgen" and, as a result, there is some amount of effort needed to migrate an existing verification environment to fully leverage the power of IntelliGen.  One of the main steps in migrating code is running the linters on your code and adressing the issues highlighted. 

Included below is a simple utility you can include in your environment that allows you to collect some valuable statistics about your code base to allow you to better gauge the amount of work that might be required to migrate from Pgen to IntelliGen.  The ICFS statistics reported are of particular benefit as the utility not only identifies the approximate number of ICFSs in the environment, it also breaks the total number down according to generation contexts (structs/units and gen-on-the-fly statements) allowing you to better focus your migration efforts. 

IMPORTANT: Sometimes a given environment can trigger a large number of IntelliGen linting messages right off the bat.  Don't let this freak you out!  This does not mean that migration will be a long effort as quite often some slight changes to an environment remove a large number of identified issues.  I recently encountered a situation where a simple change to three locations in the environment, removed 500+ ICFSs!

The methods included in the utility can be used to report information on the following:
- Number of e modules
- Number of lines in the environment (including blanks and comments)
- Number and type of IntelliGen Guidelines linting messages
- Number of Inconsistently Connected Field Sets (ICFSs)
- Number of ICFS contexts and how many ICFSs per context
- Number of soft..select overlays found in the envioronment
- Number of Laces identified in the environment

To use the code below, simply load it before/after loading e-code and then
you can execute any of the following methods:

- sys.print_file_stats()             : prints # of lines and files
- sys.print_constraint_stats()   : prints # of constraints in the environment
- sys.print_guideline_stats()    : prints # of each type of linting message
- sys.print_icfs_stats()            : prints # of ICFSs, contexts and #ICFS/context
- sys.print_soft_select_stats() : prints # of soft select overlay issues
- sys.print_lace_stats()           : *Only works for SPMNv6.2s4 and later* prints # of laces identified in the environment

Each of the above calls to methods produces it's own log files (stored in the current working directory) containing relevant information for more detailed analysis.
- file_stats_log.elog : Output of "show modules" command
- constraint_log.elog : Output of the "show constraint" command
- guidelines_log.elog : Output of "gen lint -g" (with notification set to MAX_INT in order to get all warnings)
- icfs_log.elog       : Output of "gen lint -i" command
- soft_select_log.elog: Output of the "gen lint -s" command
- lace_log.elog       : Output of the "show lace" command

Happy generating!

Corey Goss

Question for forum:

I’m currently working on a code to automatically add CLP files to DRA files and then add two classes called “APPROVED” and “CLP”. To do this manually you have to open a DRA file, click file import subdrawing and choose the clp file with the same name as dra. (path already set). You then set the clp to position x 0 0. And then click on Set Up > Subclasses > Package geometry and type in “Approved” and “Clp.”

So far we’ve recorded the macros in Allegro for all of these actions. The macros correspond to one specific file name and we want to apply this to numerous files. To do this we created a python program that locates all of the specified CLP and DRA files, and if they have a matching name, runs a for loop that puts each file name into a stored variable that runs a loop for each file. We converted this script into batch and then added a function that we thought would run Allegro macros from batch.

In order to get the script working, we need to have an allegro batch command that will run the script without opening the Allegro start popup, or closing the popup when it appears.  We need to do this to run any script from starting Allegro.

I’ve done another similar program in batch where I made a for loop for each dra file and within the loop there was a batch a2dxf command that converted all dra files to dxf files. Is there a similar batch command for adding clp files to position 0 0 and/ or adding classes? If anyone has done something similar please let me know!

Thank you very much for the help.

Jen

Dear

I want to automate the synthesis of 100 IP cores so i wrote a small script (see below),

 but i am stuck on <rc>

In easy way, rc seems does not like be called in a shallscript

To make it works i need get in each folder, call the rc and then run <souce synth.tcl>

Please anyone know how can i by pass the problem ?

Thank you so much

foreach i(*.C)

    cd $i   
    rc
    source synth.tcl
   
    cd ..
end

Can anyone tell me how i can supress few strings or integers while reading with $sscanf.

I read a line from a file into a string. there are few strings and integers seperated by white spaces in the line. I am interested in one string which comes at postion 5 in the line. how can i suppress all other strings and integers with $scanf.

i tried the following syntax but it dint work.

 $sscanf(line,"* * * * %s",string_arg);

i am tring to supress first 4 integers/strings in the line.

i had encountered error message like this before. 

but in liberate, i did not find the entry to input section info. 

Hi,

I am currently struggling with measuring the delay between two clocks with a sufficient accuracy. The reference one is a fixed-phase clock, and the other one is a squared clock resulting of a circuit (kind of PLL) synthesis.
As I need to run a large amount of Monte-Carlo simulations in transient noise, I need to improve the simulation speed, while keeping a satisfactory delay measurement accuracy (<0.1ps), more specifically at 0V-crossings of the differential clocks. So I cannot simply set a max timestep <0.1ps as it would be far too long to simulate.
To sum up, I would need a very relaxed timestep on clock up and down levels, and a very short timestep only at rise/fall transitions.

For this purpose, I wrote a Verilog-A script
- using a timmer function to accurately emulate the reference clock 0V-crossing times (and get the related times with $abstime)
- using @(cross to get the 0V-crossing times of the synthesized clock: but this is not accurate enough (I see simulation noise around 3ps in Conservative). Indeed, the "cross" event occures at the simulation time following the effective 0V-crossing time; this could be sometimes >3ps, far not enough accurate for my purpose.
- I have tried to replace the cross with the "above" function, but it hasn't changed anything, whatever the time_tol value I put (<0.1ps for instance), the result is the same as with the "cross" function and the points are larger than >>0.1ps, weirdly.

So I have decided to give up Verilog-A to measure the delay between my two clocks.
I am currently trying to use the "delay" function of the Cadence Calculator as I guess it will "extrapolate" the time between two simulation points and therefore give a more accurate measurement of the 0V-crossing events, but when I try to compute the delay difference between the synthesized clock and the reference clock, it returns "0".

...

Could you please give me hints to dramatically improve my 0V-crossing time measurements while relaxing the simulation time?
- either by helping me in writing a more suitable Verilog-A script
- or by helping me in using the "delay" function of the calculator
- or maybe by providing me a "magic" Skill function?
Using AMS+Multithread simulator...

Thanks a lot in advance for your help and best regards.

I have a question regarding simulating IBIS model using Spectre.  IBIS model generation always has the die capacitance included and in the generated IBIS file you will have this value as  “C_comp” value.  Does the Spectre accounts for this capacitance from the IBIS file while computing the time domain voltage waveform during simulation ?  If I add additional capacitance outside in the testbench, to model the die capacitance, then it will be double counting.

Does anyone know if Spectre is already accounting this C_comp during the time domain voltage wave computation from IBIS file, during simulation ?

Hello,

I find a strange issue when using design variable -> right-click -> copy from cellview in assembler. Cadence version is IC618-64b. 500.9

In fact, I set the value of variable (e.g., AAA = 100), then after I right-click -> copy from cellview, AAA's is updated to other value. In my opinion "copy from cellview" should only update the missing variable to the list, but not change any variable value. 

Is there any mechanism could change variable value when using "copy from cellview"?

Thanks

Hi,

I am trying to characterize a D flip-flop for low voltage operation (0.6V) using Cadence Liberate (V16). This is a positive edge triggered D flip flop based on true-single-phase clocking scheme. After the characterization, the measurements reported for hold constraint arcs seem to deviate significantly from its (spectre) spice simulation.

The constraint and the power settings to the liberate are as follows : 

# -------------------------------------------- Timing Constraints --------------------------------------------------------------------------------
### Input waveform ###
set_var predriver_waveform 2;# 2=use pre-driver waveform
### Capacitance ###
set_var min_capacitance_for_outputs 1;# write min_capacitance attribute for output pins
### Timing ###
set_var force_condition 4
### Constraint ###
set_var constraint_info 2
#set_var constraint_search_time_abstol 1e-12 ;# 1ps resolution for bisection search
set_var nochange_mode 1 ;# enable nochange_* constraint characterization
### min_pulse_width ###
set_var conditional_mpw 0
set_var constraint_combinational 2

#---------------------------------------------- CCS Settings ----------------------------------------------------------------------------------------
set_var ccsn_include_passgate_attr 1
set_var ccsn_model_related_node_attr 1
set_var write_library_is_unbuffered 1

set_var ccsp_min_pts 15 ;# CCSP accuracy
set_var ccsp_rel_tol 0.01 ;# CCSP accuracy
set_var ccsp_table_reduction 0 ;# CCSP accuracy
set_var ccsp_tail_tol 0.02 ;# CCSP accuracy
set_var ccsp_related_pin_mode 2 ;# use 3 for multiple input switching scnarios and Voltus only libraries

#----------------------------------------------- Power ---------------------------------------------------------------------------------------------------
### Leakage ###
set_var max_leakage_vector [expr 2**10]
set_var leakage_float_internal_supply 0 ;# get worst case leakage for power switch cells when off
set_var reset_negative_leakage_power 1 ;# convert negative leakage current to 0

### Power ###
set_var voltage_map 1 ;# create pg_pin groups, related_power_pin / related_ground_pin
set_var pin_based_power 0 ;# 0=based on VDD only; 1=power based on VDD and VSS (default);
set_var power_combinational_include_output 0 ;# do not include output pins in when conditions for combinational cells

set_var force_default_group 1
set_default_group -criteria {power avg} ;# use average for default power group

#set_var power_subtract_leakage 4 ;# use 4 for cells with exhaustive leakage states.
set_var subtract_hidden_power 2 ;# 1=subtract hidden power for all cells
set_var subtract_hidden_power_use_default 3 ;# 3=subtract hidden power from matched when condition then default group
set_var power_multi_output_binning_mode 1 ;# binning for multi-output cell considered for both timing and power arcs
set_var power_minimize_switching 1
set_var max_hidden_vector [expr 2**10]
#--------------------------------------------------------------------------------------------------------------------------------------------------------------

I specifically used set_var constraint_combinational 2 in the settings, in case the Bisection pass/fail mode fails to capture the constraints. In my spice simulation, the hold_rise (D=1, CLK=R, Q=R) arc at-least requires ~250 ps for minimum CLK/D slew combination (for the  by default smallest capacitive load as per Liberate)  while Liberate reports only ~30 ps. The define_cell template to this flip flop is pretty generic, which does not have any user specified arcs. So which settings most likely affecting the constraint measurements in Liberate and how can I debug this issue ?

Thanks

Anuradha

Dear All,
When I want to start simulation with spectre the error says:
Fatal error: Illegal library definition found in netlist
I set the model file correctly, but I don't know why it errors!
I opened the ADE>>Setup>>Model library
and I tried to modify the path of models file (SCS files)
It gives me "Illegal library definition found in netlist"
Thanks.

Hello,

I am trying to import (in spectre) an spice model of a ceramic capacitor manufactured by Samsung EM. The link that includes the model is here :-

http://weblib.samsungsem.com/mlcc/mlcc-ec.do?partNumber=CL05A156MR6NWR

They proved static spice model and interactive spice model.

I had no problem while including the static model.

However, the interactive model which models voltage and temperature coefficients seems to not be an ordinary spice model. They provide HSPICE, LTSPICE, and PSPICE model files and I failed to include any of them.

Any suggestions ?

Hello,

I am using ultrasim Version 18.1.0.314.isr5  64bit 03/26/2019 06:33 (csvcm20c-2).

When I run my netlist, ultrasim is blocked in the first DC stage and takes forever. Then it will fail or never progress. I am using a 22nm BSIMBULK model. I tried to tune different accuracy and convergence aids options but noting works.

 When I run the same netlist with spectre it works fine with no problem.

Also, If I use another model (not BULKSIM), ultrasim will work and converge with no problem.

My first feeling is that ultrasim has a problem with using BSIMBULK model.

Could you please advice,

Thank you,

Kotb

Hi,

This question is related to the constraint measurement criteria used by the Liberate inside view. I am trying to characterize a specific D flip-flop for low voltage operation (0.6V) using Cadence Liberate (V16). 

When the "define_arcs" are not explicitly specified in the settings for the circuit (but the input/outputs are indeed correct in define_cell), the inside view seems to probe an internal node (i.e. master latch output)  for constraint measurements instead of the Q output of the flip flop. So to force the tool to probe Q output I added following coder in constraint arcs :

# constraint arcs from CK => D
define_arc
-type hold
-vector {RRx}
-related_pin CP
-pin D
-probe Q
DFFXXX

define_arc
-type hold
-vector {RFx}
-related_pin CP
-pin D
-probe Q
DFFXXX

define_arc
-type setup
-vector {RRx}
-related_pin CP
-pin D
-probe Q
DFFXXX

define_arc
-type setup
-vector {RFx}
-related_pin CP
-pin D
-probe Q
DFFXXX

with -probe Q liberate identifies Q as the output, but uses Glitch-Peak criteria instead of delay degradation method. So what could be the exact reason for this unintended behavior ? In my external (spectre) spice simulation, the Flip-Flop works well and it does not show any issues in the output delay degradation when the input sweeps.

Thanks

Anuradha

Before I ask this, I am aware that I can output an s-parameter file from an SP analysis.

I'm wondering if there is a simple way of creating an s-parameter model of a component.

As an example, if I have an S-parameter model that has 200 ports and 150 of those ports are to be connected to passive components and the remaining 50 ports are to be connected to active components, I can simplify the model by connecting the 150 passive components, running an SP analysis, and generating a 50 port S-parameter file.

The problem is that this is cumbersome. You've got to wire up 50 PORT components and then after generating the s50p file, create a new cellview with an nport component and connect the 50 ports with 50 new pins.

Wiring up all of those port components takes quite a lot of time to do, especially as the "choosing analyses" form adds arrays in reverse (e.g. if you click on an array of PORT components called X<0:2> it will add X<2>, X<1>, X<0> instead of in ascending order) so you have to add all of them to the analyses form manually.

Is any way of taking a schematic and running some magic "generate S-Parameter cellview from schematic cellview"  function that automates the whole process?

In this blog, I will brief you about two very useful Rapid Adoption Kits (RAKs) for Liberate LV Library Validation.(read more)

Key Findings:  Nearly 100% of SoCs are mixed-signal to some extent.  Every one of these could benefit from the use of a metrics-driven unified verification methodology for mixed-signal (MD-UVM-MS), but the modeling step is the biggest hurdle to overcome.  Without the magical models, the process breaks down for lack of performance, or holes in the chip verification.

In the last installment of The Low Road, we were at the mixed-signal verification party. While no one talked about it, we all saw it: The party was raging and everyone was having a great time, but they were all dancing around that big elephant right in the middle of the room. For mixed-signal verification, that elephant is named Modeling.

To get to a fully verified SoC, the analog portions of the design have to run orders of magnitude faster than the speediest SPICE engine available. That means an abstraction of the behavior must be created. It puts a lot of people off when you tell them they have to do something extra to get done with something sooner. Guess what, it couldn’t be more true. If you want to keep dancing around like the elephant isn’t there, then enjoy your day. If you want to see about clearing the pachyderm from the dance floor, you’ll want to read on a little more….

Figure 1: The elephant in the room: who’s going to create the model?

 Whose job is it?

Modeling analog/mixed-signal behavior for use in SoC verification seems like the ultimate hot potato.  The analog team that creates the IP blocks says it doesn't have the expertise in digital verification to create a high-performance model. The digital designers say they don’t understand anything but ones and zeroes. The verification team, usually digitally-centric by background, are stuck in the middle (and have historically said “I just use the collateral from the design teams to do my job; I don’t create it”).

If there is an SoC verification team, then ensuring that the entire chip is verified ultimately rests upon their shoulders, whether or not they get all of the models they need from the various design teams for the project. That means that if a chip does not work because of a modeling error, it ought to point back to the verification team. If not, is it just a “systemic error” not accounted for in the methodology? That seems like a bad answer.

That all makes the most valuable guy in the room the engineer, whose knowledge spans the three worlds of analog, digital, and verification. There are a growing number of “mixed-signal verification engineers” found on SoC verification teams. Having a specialist appears to be the best approach to getting the job done, and done right.

So, my vote is for the verification team to step up and incorporate the expertise required to do a complete job of SoC verification, analog included. (I know my popularity probably did not soar with the attendees of DVCON with that statement, but the job has to get done).

It’s a game of trade-offs

The difference in computations required for continuous time versus discrete time behavior is orders of magnitude (as seen in Figure 2 below). The essential detail versus runtime tradeoff is a key enabler of verification techniques like software-driven testbenches. Abstraction is a lossy process, so care must be taken to fully understand the loss and test those elements in the appropriate domain (continuous time, frequency, etc.).

Figure 2: Modeling is required for performance

AFE for instance

The traditional separation of baseband and analog front-end (AFE) chips has shifted for the past several years. Advances in process technology, analog-to-digital converters, and the desire for cost reduction have driven both a re-architecting and re-partitioning of the long-standing baseband/AFE solution. By moving more digital processing to the AFE, lower cost architectures can be created, as well as reducing those 130 or so PCB traces between the chips.

There is lots of good scholarly work from a few years back on this subject, such as Digital Compensation of Dynamic Acquisition Errors at the Front-End of ADCS and Digital Compensation for Analog Front-Ends: A New Approach to Wireless Transceiver Design.

Figure 3: AFE evolution from first reference (Parastoo)

The digital calibration and compensation can be achieved by the introduction of a programmable solution. This is in fact the most popular approach amongst the mobile crowd today. By using a microcontroller, the software algorithms become adaptable to process-related issues and modifications to protocol standards.

However, for the SoC verification team, their job just got a whole lot harder. To determine if the interplay of the digital control and the analog function is working correctly, the software algorithms must be simulated on the combination of the two. That is, here is a classic case of inseparable mixed-signal verification.

So, what needs to be in the model is the big question. And the answer is, a lot. For this example, the main sources of dynamic error at the front-end of ADCs are critical for the non-linear digital filtering that is highly frequency dependent. The correction scheme must be verified to show that the nonlinearities are cancelled across the entire bandwidth of the ADC. 

This all means lots of simulation. It means that the right level of detail must be retained to ensure the integrity of the verification process. This means that domain experience must be added to the list of expertise of that mixed-signal verification engineer.

Back to the pachyderm

There is a lot more to say on this subject, and lots will be said in future posts. The important starting point is the recognition that the potential flaw in the system needs to be examined. It needs to be examined by a specialist.  Maybe a second opinion from the application domain is needed too.

So, put that cute little elephant on your desk as a reminder that the beast can be tamed.

Steve Carlson

Related stories

- It’s Late, But the Party is Just Getting Started

Verification is the top challenge in mixed-signal design. Bringing analog and digital domains together into unified verification planning, simulating, and debugging is a challenging task for rapidly increasing size and complexity of mixed-signal designs. To more completely verify functionality and performance of a mixed-signal SoC and its AMS IP blocks used to build it, verification teams use simulations at transistor, analog behavioral and real-number model (RNM) and RTL levels, and combination of these.

In recent years, RNM and simulation is being adopted for functional verification by many, due to advantages it offers including simpler modeling requirements and much faster simulation speed (compared to a traditional analog behavioral models like Verilog-A or VHDL-AMS). Verilog-AMS with its wreal continue to be popular choice. Standardization of real number extensions in SystemVerilog (SV) made SV-RNM an even more attractive choice for MS SoC verification.

Verilog-AMS/wreal is scalar real type. SV-RNM offers a powerful ability to define complex data types, providing a user-defined structure (record) to describe the net value. In a typical design, most analog nodes can be modeled using a single value for passing a voltage (or current) from one module to another. The ability to pass multiple values over a net can be very powerful when, for example, the impedance load impact on an analog signal needs to be modeled. Here is an example of a user-defined net (UDN) structure that holds voltage, current, and resistance values:

When there are multiple drives on a single net, the simulator will need a resolution function to determine the final net value. When the net is just defined as a single real value, common resolution functions such as min, max, average, and sum are built into the simulator.  But definition of more complex structures for the net also requires the user to provide appropriate resolution functions for them. Here is an example of a net with three drivers modeled using the above defined structural elements (a voltage source with series resistance, a resistive load, and a current source):

To properly solve for the resulting output voltage, the resolution function for this net needs to perform Norton conversion of the elements, sum their currents and conductances, and then calculate the resolved output voltage as the sum of currents divided by sum of conductances.

With some basic understanding of circuit theory, engineers can use SV-RNM UDN capability to model electrical behavior of many different circuits. While it is primarily defined to describe source/load impedance interactions, its use can be extended to include systems including capacitors, switching circuits, RC interconnect, charge pumps, power regulators, and others. Although this approach extends the scope of functional verification, it is not a replacement for transistor-level simulation when accuracy, performance verification, or silicon correlation are required:  It simply provides an efficient solution for discretely modeling small analog networks (one to several nodes).  Mixed-signal simulation with an analog solver is still the best solution when large nonlinear networks must be evaluated.

Cadence provides a tutorial on EEnet usage as well as the package (EEnet.pkg) with UDN definitions and resolution functions and modeling examples. To learn more, please login to your Cadence account to access the tutorial.

Bumps are central to the Virtuoso MultiTech Framework solution. Bumps provide a connection between stacked ICs, interposers, packages, and boards. Bump locations, connectivity, and other attributes are the basis for creating TILPs, which we combine to create system-level layouts.(read more)

Here is another blog in the multi-part series that aims at providing in-depth details of electromagnetic analysis in the Virtuoso RF solution. Read to learn about the nuances of port setup for electromagnetic analysis.(read more)

If you have one of those Die layouts, which doesn’t have bumps, but rather uses pad shapes and labels to identify I/O locations, then you might be feeling a bit left out of all of this jazz and tango. Hence, today, I am writing to tell you that, fear not, we have a solution for your Die as well.(read more)

We have all heard the sayings “Less is more” and “Keep it simple”. Electromagnetic simulation is an activity where following that advice has enormous payoffs. In this blog I’ll talk about some of my experiences with how Virtuoso RF Solution’s shape simplification feature has helped my customers get significant performance improvements with minimal impacts on accuracy. (read more)