Hi Sharjeel, I would suggest contact customer support about this. Other may have the bandwidth to investigation this in depth, but I don't myself (a bit busy at the moment with the day job and so I can only answer questions that are quick to answer and don't involve too much experimentation and investigation). Andrew.![]()
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RE: Harmonic Index of PSS data is not found?
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RE: Harmonic Index of PSS data is not found?
I want to second what Andrew Beckett has stated. This really needs to be handled by an Application Engineer in Customer Support. We answer these questions in our "off hours" after we've been at our "day jobs". The appnote that you are referring to " Jitter Measurements using Spectre RF AN" is about 15 years old (or older). It is always best to use the Spectre and APS RF User Guide for guidance. It's the most up-to-date information available. We've changed our pnoise setups (and how we calculate some of the pnoise parameters) since those two appnotes/papers were written. IF the analyses are set up properly, the Shooting Newton engine should give the same results as the Harmonic Balance engine. You need to use the most appropriate tool for the job, however. Very fast rise times, periodic switching circuits do better with Shooting pss/pnoise. Mildly nonlinear circuits are best handled with HB/hbnoise. All things that I believe Andrew has mentioned. best regards, Tawna![]()
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Bus pin mapping in layout
Dear experts, When generating or placing pins from schematic to layout, how control mapping of bus pins? Say how to map sel schematic pin to sel[0] and sel[1] layout pins. Thanks Norayr![]()
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Allegro PCB Designer auto-routing
Hello, i'm a student studying Allegro and want to know about auto-routing function. When the tool routes automatically, is this function grid-based? If so, how much is the grid size set to this function? Thank you.![]()
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allegro skill system() function
Hi I met a problem about the function system(), for example: I try to get current time by system() Skill > system("date") 1 Skill > why does it return 1 ? I need like this: Wed Dec 14 15:14:53 PST 1994 anyone can help that? many thanks![]()
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RE: AMS Simulation Error for INCISIV Version
Thank you.![]()
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Amplitude sweep in VERILOG-A environment to generate multiple Output files through the Verilog-A code
I am doing a simulation in Cadence for a Delta-Sigma ADC with blocks like op-amp and Quantizer modeled in Verilog-A environment . The quantizer is a single-bit quantizer and hence modelled just as a comparator that works on a clock with V(out) = +1 when the V(in) > 0 and V(out) = -1 when the V(in) < 0. In the quantizer block, I have a c ode piece that does a file export in .dat format (@filecheck (path of the destination to store the file)). This is performed because I will load this file generated into Matlab and verify the performance metrics like SNR and IBN through the code run in Matlab. Now I want to sweep that amplitude lets say for 100 levels between a minimum and maximum. With this, I would like to generate 100 file outputs on each iteration such that I can load that in Matlab using an iteration of 100 levels. How can I modify the Verilog-A code so as to generate each file at each amplitude iteration without just replacing the existing file each time ?![]()
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RE: allegro skill system() function
Hi! try this getCurrentTime() Luan![]()
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RE: allegro skill system() function
Yes, thank you! but how can I get other commands of linux?![]()
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cannot open file for edit in VSE
Hello All, i copied a design from a colleague but when i am trying to open any of the schematics its only giving the option to open it in read only mode. I have deleted the lck files and have write permissions in the work area as well as this copied design. When i go to Edit -> Access Permissions in the Library manager i see the below. can anyone please advise how can i open the schematics in EDIT mode? I have IC6.1.7 thanks![]()
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How to access a variable one level above prog() if not declared in current prog()
Hello All, To avoid using a long name (such as proABC.localVar1 ), how do I access the variable "localVar1" that is outside current prog()? ----------------------------------------------------------------------------------------------------------------- procedure(proABC() prog( (localVar1) localVar1 = 1 if( (t) then prog( () localVar1 = 3 ;; note I did not declare any variable named "localVar1" in this prog(). I would expect this to use the variable declared earlier printf( "localVar1 in IF statement = %d " localVar1) ;; this prints 3 ) ) printf( "localVar1 outside IF statement = %d " localVar1) ;; this prints 1 ) ) ----------------------------------------------------------------------------------------------------------------- Thanks All![]()
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RE: Exit axlSingleSelectPoint(nil) from blocking other code
Thank you. I will try that.![]()
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Detecting existence of cds_global variable in AMS
I can reference a cds_global variable in a verilogams view by using cds_globals.variableName. However, I'd like to be able to test its existence, and the to set it to a default value if it is not defined by the user. Something like the below... if(exists cds_globals.signalName) output=cds_globals.signalName; else output = 7; Is there a way to do this? I tried "`ifdef / `elsif / `endif" and that always followed the "elsif" path.![]()
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RE: Harmonic Index of PSS data is not found?
Thanks Andrew/ Tawna. There is indeed a gamut of info available in Cadence Spectre docs and i do have access to all of these from Jan, 2020 (spectreRFTheory, sectreRFinExplorer, spectreRFexplorerWorkshop, etc) but to my knowledge (correct me if I am wrong) unfortunately none of these deal with the underlying formula for different jitter definitions except the AN which I mentioned, which is why I have also referenced Lee's paper to corroborate the theory in the said AN. However, i will get in touch with an applications engineer and see what they say. Regards, Sharjeel![]()
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RE: BSIM4 import into AWR
Hi Graeme, Many thanks for the reply, much appreciated. I have used this template and imported the BSIM variables manually and converted all the complex equations to values and it is working now (at least the DC part). Yet to test the AC and nonlinear HB but at least the sim is running now without errors. Only thing is that I am getting a couple of warnings: "Source conductance reset to 1.0E3mho. (BSIM4!_S1_nfet33)", and "Drain conductance …." (where nfet33 is my devicename) Doesn't make much sense as when I change the w, the Drain current seems to scale correctly. Just wondering if you know what these warnings refer to? Best Regards, Chris.![]()
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5G: Connecting All the Things
Over the last few weeks, each Thursday has been Telecom Thursday (like Taco Tuesday but with guacamobile). Well, except for last week since Cadence had a surprise 4-day holiday weekend announced at the last minute. 1G Mobile: AMPS, TOPS, C-450, Radiocom 2000, and All Those Japanese Ones 2G: Mobile Goes Digital 3G and 4G: The Internet Arrives Now we come to 5G. In the long run, the world will move to 5G. But in the short run, it just sounds as if it will. In fact, the numbers from the Consumer Electronics Association (who run CES) is that in the US just 20M handsets are forecast to be 5G this year, out of total forecast shipments of 166M. But the forecast for 2021 triples, to 60M out of 167M, as you can see from the chart below. By the way, this chart looks like it is showing the fractions of 100% that go to 5G and 4G, but actually it is a bar graph showing total shipments. The total market in the US is mature and is a replacement market, and it is essentially flat from 2018 to 2023. Despite all the hype, it is 2021 not 2020 that will really be the era of 5G. My expectation is that by the end of 2021, we will see 5G in major cities and perhaps along the busiest interstate highways. But in rural areas, it will still be 4G and LTE (although AT&T will call this 5G anyway). In a lot of the world, 2G and 3G will continue to be the dominant technologies: they ain't broke so don't fix 'em. 5G is a number of technologies rolled up under one umbrella name. Frequencies First, there are three bands of spectrum, known as "low band", "medium band", and "mmWave" (sometimes called "high band"). The low and medium spectrum is often grouped as "sub-6GHz" since those are the radio frequencies used. I don't like "high band" and always say "mmWave" because that band is not the next band up from medium. Medium can go as high as 6GHz, but mmWave starts at 25GHz. There is an enormous gap, and the radio technologies and characteristics of the two lots of spectrum are very different. The precise frequencies actually available vary by country. In particular, the US has a lot of government, military, and satellite spectrum already allocated in what should be the medium band. The FCC is trying to clear some of this, but it is progressing only slowly. The big differences between sub-6GHz and mmWave are two-fold. First, sub-6GHz can do something that we are used to with our phones, they work indoors even though the basestations are outdoors. The mmWave band is such high frequency that it cannot go through walls and windows, or even a lot of air, where its range is limited to about 300m. There is no mobile phone spectrum in-between sub-6GHz and mmWave. On the other hand, there are almost unlimited amounts of bandwidth with mmWave since there is a lot of spectrum. The thing to avoid doing is expecting to get all the advantages of mmWave (fast speeds, lots of spectrum) in the sub-GHz bands (good building and air penetration). Expect the mobile operators to do their best to confuse you about this in their marketing. Access Protocols Prepare for a salad of acronyms. There are four major use cases for 5G: fixed wireless access (FWA), enhanced mobile broadband (eMBB), massive machine-type communications (MTC), and ultra-reliable low-latency communication (URLLC). Fixed Wireless Access (FWA) There is an expectation that a major use case for 5G will be to provide internet access to homes in competition with cable TV, DSL, and satellite. This would use mmWave. Other spectrum is too valuable and has too little bandwidth. Since mmWave won't penetrate buildings and will only go about 300m, this would require some sort of fixed tower, with line-of-sight connectivity to an antenna on the outside of each house. Verizon started trials of fixed wireless as long ago as 2018 in 11 markets. Enhanced Mobile Broadband (eMBB) This is just better smartphones. You might get higher bandwidth under perfect circumstances, but I think the most likely difference that you will notice from 4G is that there is more network capacity and so you are more likely to be able to get a good data connection even when there are a large number of phones around such as at a major technology trade-show. You are unlikely to notice much difference in transmission speeds on your phone since you typically don't download large files. The largest files are videos, and you simply watch them. If you tether your laptop to your phone, and then start copying large files around, you should see a difference (again, assuming ideal connectivity conditions). One thing that 5G can do, if the network is lightly loaded, is to combine multiple channels that would otherwise be used by two separate phones. It seems that there are big differences between a lightly loaded network with line of sight to a basestation, compared to a heavily loaded network with obstacles around. A 5G network cannot assume that all users already have a 5G smartphone, and it will be several years before that is even close to true. So 4G services (and perhaps older) also need to be provided from the same basestation, what I suppose we might call "unenhanced mobile broadband". eMBB is likely to be the main focus of 5G as it starts to roll out over the next few years. Even though 5G is about connecting "things" more than people, the initial focus is likely to be plain mobile broadband, since that's where the business models and demand are well-understood. By the way, "plain mobile broadband" is not actually an official phrase, as far as I know. But Plain Old Telephone Service, or POTS, is the industry name for normal wireline phone service, with no digital stuff like DSL involved. In fact, when DSL was first proposed, it was expected that houses would have a "POTS splitter" that separated the digital broadband from normal phone calls. In the end, it was simpler just to put filters on all the POTS phones so that the digital data didn't interfere with the audio. Massive Machine-Type Communications (mMTC) This is the migration path for NB-IoT and LTE-M. NB-IoT is "narrowband internet-of-things". LTE-M is the version of LTE aimed at machines (M apparently stands for "Machine Type Communication" which is a lot of words for one initial). Both of these approaches are intended to support a huge number (think millions) of devices that don't transfer much data at all. These could range from devices spread through a farmer's fields to detect moisture and temperature, to smart security cameras that keep quiet except when they detect something where the alarm has to be raised, or perhaps city garbage cans that signal when they need emptying. All three of these use cases are things that really exist already. These protocols are the opposite of watching a video on mobile, a few kilobits of data occasionally is all that is needed. But there are likely to be many more of these "things" than there are mobile phones (and there are already billions of them). Ultra-Reliable Low-Latency Communication (URLLC) This is what it sounds like, mission-critical network services for IoT. I'm not entirely convinced that all the things that pundits expect this to be used for are realistic. For example, RCR Wireless News says: URLLC will cater to multiple advanced services for latency-sensitive connected devices, such as factory automation, autonomous driving, the industrial internet, and smart grid or robotic surgeries. Well, maybe. I just think that it is unlikely that anyone is going to be connecting up their factory automation using a 5G network, as opposed to hard-wired (or even optical), or some sort of privately owned network more akin to your WiFi router at home. Of course, it all depends on how reliable...but the idea that my surgeon has me opened up and then loses 5G connectivity is not something I want to go near. Network Slicing The challenge for a 5G network operator is to support all of these technologies on the same network. They have different requirements in terms of bandwidth requirements, latency requirements, and reliability requirements. This necessitates dividing up the network resources in a way that each connection gets appropriate service guarantees and isolation from other services. mmWave has a whole set of its own challenges, some technical, some regulatory, and some political. The fact that it only goes a limited distance in air means that it only makes sense in areas where a high density of small basestations can be deployed, such as in urban areas with a basestation on every street light or telephone pole. Unlike existing large basestation towers, the cellular carriers have no rights to street lights, so getting those rights will not be instantaneous. Some jurisdictions are likely to introduce similar rules to those when cable-TV was first deployed, forcing the existing owners of poles to share them. Nobody wanted another set of poles in every neighborhood. But there is a lot of emotional opposition to basestations. I read an interesting article that I forgot to note down about one of the cellular operators having to constantly go to neighborhood meetings where person after person would complain that they never had a headache before in their life and now they are in constant pain, and it is all due to the cell tower. Then, after everyone had had their say, he would point out that they hadn't turned the basestation on yet, they just put up the tower. When, after a couple of months, they did turn on the tower, nobody would notice. One other point he made, which is a bit of an LOL, is that if you are concerned about cellular radiation and schools, then absolutely the best place to put a basestation is on the school roof. There is actually a sort of radio shadow underneath the tower since the antennas face out. Of course, the cellphone reception in the school would be poor...but kids aren't meant to be on their cellphones all the time anyway. Learn More A little bit of revision. Learn these terms if you have anything to do with 5G — you will see them a lot: eMBB (enhanced Mobile Broadband) URLLC (Ultra Reliable Low Latency Communications) mMTC (massive Machine Type Communications) And if what you have to do with 5G is designing electronics, then Cadence has various tools and IP specifically 5G. See 5G Systems and Subsystems on the Cadence website. Sign up for Sunday Brunch, the weekly Breakfast Bytes email.![]()
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RE: BSIM4 import into AWR
Hi Chris, I wouldn't worry about that warning, these relate to DC operating points calculated by APLAC representing the internal terminal resistance. If this isn't being calculated from the given parameter set then forcing a small resistance aids convergence. Graeme![]()
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RE: Allegro PCB Designer auto-routing
Gridless routing isn't always gridless, Allegro or Expedition. Cadence adheres to the route grid setting unless gloss/centering or using the bubble/hug option for interactive routing.![]()
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RE: Sub Menus are too large
That was something I hadn't thought of! Unfortunately those are already the current settings...![]()
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Library Characterization Tidbits: Overriding the One-Sigma Rule of Liberty for LVF Modeling
In the last few blogs of this series, we have examined some unique features of Cadence ® Liberate TM Characterization , Liberate MX , Liberate AMS , Liberate LV , and Liberate Trio . How about looking into the Liberate Variety TM statistical characterization solution this time? As per Liberty specification, Liberty Variation Format (LVF) modeling is always done at one-sigma. However, did you know that Liberate Variety supports unique settings for characterization and LVF modeling? These settings allow you to use different sigma values for variation parameters and data types such as delay, setup, hold, and so on. Identify the Variation Parameters The first step to override the one-sigma rule is to determine the variation parameters that need to be characterized. In Liberate Variety, you do this using the define_variation command. The information about the variation parameters can be obtained from the foundry. For example, the table below illustrates the syntax and meaning of the variation parameters in a model file of SPICE and Spectre formats. It is noteworthy that the last case shown in the table is mathematically possible, but never encountered. SPICE Format Spectre Format Meaning parl1=agauss (0,1,1) parl2=agauss (0,1,1) … … vary parl1 dist=gauss std=1/1 vary parl2 dist=gauss std=1/1 … … Absolute variation at 1-sigma is 1 parl1=agauss (0,1,3) vary parl1 dist=gauss std=1/3 Absolute variation at 3-sigma is 1 parl1=agauss (0,3,3) vary parl1 dist=gauss std=3/3 Absolute variation at 3-sigma is 3 parl1=agauss (0,3,1) vary parl1 dist=gauss std=3/1 Absolute variation at 1 sigma is 3 For example, the following commands define the variation parameters at one-sigma: define_variation –type random {parl1 1} parl1 define_variation –type random {parl2 1} parl2 Determine Different Sigma Values for Different Variation Parameters and Data Types The global parameter, variation_sigma , defines the sigma level at which to characterize. By default, variation_sigma is set to 1 and is applied to all the define_variation commands. Changing this default sigma value is not recommended. However, in Liberate Variety, you can define an absolute variation value using the -sigma option of the define_variation command. This command option treats the value in the { parameter value } pair as a sigma value. Note that the requirement here is that the SPICE models have been read and flattened so that the specified sigma value can be mapped into the real value specified in the gauss or agauss setting in the model file. To adjust the sigma value at which to characterize the variation by the data type, you need to use the define_variation_factor command. This command allows you to specify sigma values for data types such as delay , constraint , setup , recovery , non_seq_setup , hold , removal , non_seq_hold , and mpw . For example, the following command shows how to characterize delay at one-sigma, constraint at two-sigma, and all other data types at one-sigma: define_variation_factor {all 1 delay 1 constraint 2} Model with Different Sigma Factor Values for Each Variation Parameter At the time of model creation, the variation is stored in the library database (LDB) at one-sigma. Therefore, for characterizing the variation parameters at different sigma values, you need a sigma factor value to adjust the modeled variation. Liberate Variety supports this feature through the -sigma_factor option of the define_variation_group command. Using this option, you can define a multiplicative weighting factor to be applied to each variation parameter. For example, to model the variation parameters into the output library at three-sigma, set the -sigma_factor option to a value of 3 : define_variation_group –sigma_factor 3.00 {parl1 parl2} LOCAL_VARIATION How About Reviewing Some Example Scenarios Now? By now, you would know that to override the one-sigma rule of the Liberty syntax for LVF modeling, you primarily need to be familiar with the usage of the following three Liberate Variety commands: define_variation , define_variation_factor , and define_variation_group . For some useful example scenarios, refer to the How to Specify Variation Setup for LVF Characterization & Modeling application note available in the Cadence Support portal. Do try this feature of Liberate Variety, if you have not done that already. Hope you would agree with me on its usefulness. Till we meet next, take care and stay safe! ~Abha Rawat Related Resources For more information about working with the Liberate Variety statistical characterization solution, see the following documents: Liberate Variety Statistical Characterization Reference Manual Liberate Characterization Portfolio Command and Parameter Support Matrix 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.![]()
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