Hello, i saw that MAESTRO is a plotting addon is it a part of ADE EXPLORER?

i cant see the relation between the two.i started to read manual and regarding MAESTRO i only see code.

is there some simple examples?
Thanks.

Hello, i have a realy mistick thing going with copying libraries in cadence virtuoso,

When i copy straight forwart the whole library it gives me a warning that accsess was denied,but when i go into the library and copy it as a single file, then it goes fine.

another problem is it doesnt show in the massage console  ALL the files which could not be copied.(which is the much bigger problem,becuase i would have to pass threw all the subdirectories to verify if all files are there)

Is there a way to see which files wasnt able to be copied?

Thanks. 

Hi,
I am new to the circuit design and troubleshooting. My project is to design a trans-impedance amplifier using Cadence that can amplify a signal coming from a photodiode. I started out with the regulated cascode configuration as shown in the circuit below. I look at the frequency response using AC simulation and it looks like a high pass (/net 5). The results doesn ot show any gain (transient response), or expected low-pass roll-off in the AC response.

First thing, I looked into the operating regions of the MOSFETs and adjusted the input dc voltage of the Vsin to 0.5 to make sure that the T0, T1 mosfets are in saturation(checked this with the print->dc operating points). Beyond this point, I am not sure on how to proceed and interpret the results to make changes. Any help would be greatly appreciated.

Thanks,

-Rakesh.

Hello , i am trying to extract netlist from a circuit  in assembler

I have found the manual shown bellow , however there is no such option in tools in assembler.

how do i view the NETLIST of this circuit?

Thanks.

ASSEMBLER VIEW menu

Hello, I have a problem with a certain type of transistor,my hyrarchy has a lot components an sub components and visually inspecting them is very hard.

is there a way like in other cadence layout viewer tools , to enter the name of the component or a NET somewhere and it will focus on it visualy or give the hyrarchy path to it?

Thanks.

Hello

The document I referenced is https://filebox.ece.vt.edu/~symort/rfworkshop/Mixer_workshop_instruction.pdf. (This is cadence workshop document)

While following the pxf simulation in the above article, the results are different and I have a question.

My result picture is shown below.

<my result error>

<document result>

<my direct plot>

<document direct plot>

The difference with the documentation is that in the direct plot screen after the pxf simulation,

1.output harmonics-> input sideband

2.Frequency axis: out-> frequency axis: absin

3.The results for port0 (RF port) are also different (see photo below).

4.The frequency values in the box are different.

My screen shows 5G, 10G, 1K ~ 10M, but the document is the same as 1K ~ 10M.

Ask for a solution. Thank you.

Hi, all

Recently, I meet the simulation error as the picture shows when I simulate my circuit with transient.  how can I solve this problem?

thank you~

Hello, i am trying to produce a gain circles on a simple transistor as shown bellow.

i have defined the range from 1 til 30 dB and i dont get any circle just dots in infinity?

Where did i go wrong?
Thanks.

Hello, i have built a matching network of 13dB gain and  NF as shown bellow step by step.(including all the plots and matlab )

its just not working at all,i am doing it exacly by the thoery

taking a point inside the circle-> converting its gamma to Z_source->converting gamma_s into gamma_L with the formulla bellow as shown in the matlab->converting the gamma_L into Z_L-> building the matching network for conjugate of Z_L and Z_c.Its just not working.

where did i got  wrong?

Thanks.

gamma_s=75.8966*exp(deg2rad(280.88)*i);
z_s=gamma2z(gamma_s,50);
s11=0.99875-0.03202*i
s12=721.33*10^(-6)+8.622*10^(-3)*i
s21=-188.37*10^(-3)+30.611*10^(-3)*i
s22=875.51*10^(-3)-100.72*10^(-3)*i
gamma_L=conj((s22+(s12*s21*gamma_s)/(1-s11*gamma_s)))
z_L=gamma2z(gamma_L,50)

Hello, There is a manual in matlab of matching LNA  shown in the link bellow.

In it as shown in the plot bellow they mention input and output circle plots.

Is there such option of input and output circle in cadence virtuoso?

https://www.mathworks.com/help/rf/examples/designing-matching-networks-part-1-networks-with-an-lna-and-lumped-elements.html

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.

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...  

This is the 15th installment of The Rationalist, my column for the Times of India.

It’s election season, and promises are raining down on voters like rose petals on naïve newlyweds. Earlier this week, the Congress party announced a minimum income guarantee for the poor. This Friday, the Modi government released a budget full of sops. As the days go by, the promises will get bolder, and you might feel important that so much attention is being given to you. Well, the joke is on you.

Every election, HL Mencken once said, is “an advance auction sale of stolen goods.” A bunch of competing mafias fight to rule over you for the next five years. You decide who wins, on the basis of who can bribe you better with your own money. This is an absurd situation, which I tried to express in a limerick I wrote for this page a couple of years ago:

POLITICS: A neta who loves currency notes/ Told me what his line of work denotes./ ‘It is kind of funny./ We steal people’s money/And use some of it to buy their votes.’

We’re the dupes here, and we pay far more to keep this circus going than this circus costs. It would be okay if the parties, once they came to power, provided good governance. But voters have given up on that, and now only want patronage and handouts. That leads to one of the biggest problems in Indian politics: We are stuck in an equilibrium where all good politics is bad economics, and vice versa.

For example, the minimum guarantee for the poor is good politics, because the optics are great. It’s basically Garibi Hatao: that slogan made Indira Gandhi a political juggernaut in the 1970s, at the same time that she unleashed a series of economic policies that kept millions of people in garibi for decades longer than they should have been.

This time, the Congress has released no details, and keeping it vague makes sense because I find it hard to see how it can make economic sense. Depending on how they define ‘poor’, how much income they offer and what the cost is, the plan will either be ineffective or unworkable.

The Modi government’s interim budget announced a handout for poor farmers that seemed rather pointless. Given our agricultural distress, offering a poor farmer 500 bucks a month seems almost like mockery.

Such condescending handouts solve nothing. The poor want jobs and opportunities. Those come with growth, which requires structural reforms. Structural reforms don’t sound sexy as election promises. Handouts do.

A classic example is farm loan waivers. We have reached a stage in our politics where every party has to promise them to assuage farmers, who are a strong vote bank everywhere. You can’t blame farmers for wanting them – they are a necessary anaesthetic. But no government has yet made a serious attempt at tackling the root causes of our agricultural crisis.

Why is it that Good Politics in India is always Bad Economics? Let me put forth some possible reasons. One, voters tend to think in zero-sum ways, as if the pie is fixed, and the only way to bring people out of poverty is to redistribute. The truth is that trade is a positive-sum game, and nations can only be lifted out of poverty when the whole pie grows. But this is unintuitive.

Two, Indian politics revolves around identity and patronage. The spoils of power are limited – that is indeed a zero-sum game – so you’re likely to vote for whoever can look after the interests of your in-group rather than care about the economy as a whole.

Three, voters tend to stay uninformed for good reasons, because of what Public Choice economists call Rational Ignorance. A single vote is unlikely to make a difference in an election, so why put in the effort to understand the nuances of economics and governance? Just ask, what is in it for me, and go with whatever seems to be the best answer.

Four, Politicians have a short-term horizon, geared towards winning the next election. A good policy that may take years to play out is unattractive. A policy that will win them votes in the short term is preferable.

Sadly, no Indian party has shown a willingness to aim for the long term. The Congress has produced new Gandhis, but not new ideas. And while the BJP did make some solid promises in 2014, they did not walk that talk, and have proved to be, as Arun Shourie once called them, UPA + Cow. Even the Congress is adopting the cow, in fact, so maybe the BJP will add Temple to that mix?

Benjamin Franklin once said, “Democracy is two wolves and a lamb voting on what to have for lunch.” This election season, my friends, the people of India are on the menu. You have been deveined and deboned, marinated with rhetoric, seasoned with narrative – now enter the oven and vote.

The India Uncut Blog © 2010 Amit Varma. All rights reserved.
Follow me on Twitter.

Hi supporters,

I got the following error while I run simulation with gate netlist using Cadence Incisive (v15.20):

----

ncsim(64): 15.20-s076: (c) Copyright 1995-2019 Cadence Design Systems, Inc.
ncsim: *E,DLOALB: Design library 'tcbnxxx' not defined while reading module tcbnxxx.MAOxxx:bv (VST).
ncsim: *F,NOSIMU: Errors initializing simulation 'alu_tb' 

----

xxx: standard library name.

My netlist design uses a cell "MAOxxx". I already included the library behavior model to compile using ncverilog, there is no error while compiling. But when I run with ncsim to execute the test, I got above error.

I tried to run with other vendors such as VCS or MTI, they worked.

Please help to understand the error.

Thanks.

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

Specman *search* command allows searching in all loaded modules, but only for a string.

Is there a way to search for a regexp or glob?

Alternatively, is there a way to simply get a list of all loaded files somehow? Then I could use either the "shell" command, or real shell together with grep.

Thanks

We have talked about aspects of the in-design symbol edit application mode in the past. This is the environment specific to the Allegro Package Designer layout tools allowing you to work on symbol definitions directly in the context of your layout de...(read more)

Hi everyone! I'm working on a small battery powered PCB which will fit inside a small plastic "hockey puck" container. A number of these "pucks" will be sold together with a "charging doc" which will store and charge the pucks when not in use.

I'm trying to work out the best way to charge the battery. I'm thinking of having metal "pads" on the rr.com puck that pass through the puck's plastic shell and then make contact with the PCB on the inside, and having a similar system on the charging dock. I'm thinking of having SMD "contact sprints" mounted to the underside of the PCB and have these mate against metal pins that protrude through the puck, but it's the later of which I'm struggling to find. For a visual, think about "restaurant pagers" and how they charge.

Hello all,

We are designing a backplane and in the design we are using some custom prefixes using the Advance Annotation tool. When annotating the occurances I get the following error:

ERROR(ORDBDLL-1224): The total number of components for prefix J0C exceeds the range supplied for it.
Increase the End value of the range.

Thanks in advance for the help

--Tom

I'm trying to re-install ORCAD 17.2  in a PC from a DVD which I have upgraded from Win 7 to Win 10 and  now has a new 500GB SSD. While installing I got a Windows Application Error  0xc000007b. When I try to run ORCAD I get the same Error.

Looking for ways to fix this problem.

Hello All,

I'm currently using OrCAD PCB Designer Professional w/ PSpice (version 16.6-2015).  In the 'Design Object Find Filter' side bar, all options are grayed out and unselectable.  I did attempt to 'Reset UI to Cadence Default' without any luck.  A colleague has no issues with the identical file on his computer.  Any guidance would be much appreciated.  Thanks!

George

Hi everybody,

I've created a symbol with custom pad shapes. Everything looks correct in the symbol editor.

And the 3d view looks correct (upside down to show placement)

But when I try to place it on the pcb the 2 "T" shaped pads aren't in the correct location.

I have the pad shape centered on the pad...

with no offset on the padstack editor.

Does anybody know how to fix this?

Thank you!

Hi There,

The variant bom I set gone dissapear. Is there any way to recover this back from the old design file? 

This is the second time it happen to me. Not really sure what could cause this. 

Thanks,

Pornchai

Please include a brief summary of how to use it.

Hi All.

I put together a small Perl script to generate vr_ad register definitions from SPIRIT (IP-XACT) XML.
If you've got not idea what IP-XACT is, have a look here http://www.spiritconsortium.org/, then start pestering your design manager to use it :-)

The script can filter out registers and override R/W access types if needed.

An example XML file is included with the package so that you can play with it, and there's a detailed README.txt as well.

Here's an example of the generated e code:

// Automatically generated from xdmac.xml
// DO NOT EDIT, or your changes may be lost
<'

import vr_ad/e/vr_ad_top;

// Component = XDMAC
// memoryMap = xdmac
extend vr_ad_map_kind : [XDMAC];

// addressBlock = dma_eth
extend vr_ad_reg_file_kind : [DMA_ETH];

extend DMA_ETH vr_ad_reg_file {
  keep size == 20;
  keep addressing_width_in_bytes == 4;
};

// Register = command
// Reset    = 0x00
reg_def COMMAND DMA_ETH 0x0 {
  // Field resv3 = command[31:29]
  reg_fld resv3 : uint(bits:3) : R : 0 : cov ;
  // Field transfer_size = command[28:19]
  reg_fld transfer_size : uint(bits:10) : RW : 0 : cov ;
  // Field dma_transfer_target = command[18:14]
  reg_fld dma_transfer_target : uint(bits:5) : RW : 0 : cov ;
  // Field resv2 = command[13:10]
  reg_fld resv2 : uint(bits:4) : R : 0 : cov ;
  // Field transmit_receive = command[9:9]
  reg_fld transmit_receive : uint(bits:1) : RW : 0 : cov ;
  // Field resv1 = command[8:5]
  reg_fld resv1 : uint(bits:4) : R : 0 : cov ;
  // Field dest_address_enable = command[4:4]
  reg_fld dest_address_enable : uint(bits:1) : RW : 0 : cov ;
  // Field source_address_enable = command[3:3]
  reg_fld source_address_enable : uint(bits:1) : RW : 0 : cov ;
  // Field word_size = command[2:0]
  reg_fld word_size : uint(bits:3) : R : 0 : cov ;
};

// Register = queue_exec
// Reset    = 0x00
reg_def QUEUE_EXEC DMA_ETH 0x10 {
  // Field resv = queue_exec[31:1]
  reg_fld resv : uint(bits:31) : R : 0 : cov ;
  // Field exec = queue_exec[0:0]
  reg_fld exec : uint(bits:1) : RW : 0 : cov ;
};

extend XDMAC vr_ad_map {
  dma_eth : DMA_ETH vr_ad_reg_file;

  post_generate() is also {
    add_with_offset(0x00, dma_eth);
    dma_eth.reset();
  };
}
'>

Any comments, please feed them back to me so I can enhance the script.
Note that this forum forces me to post a .zip file rather than .tgz, please be careful to unpack the file under Linux, not Windows, else the DOS linefeeds will corrupt the Perl and XML files.

Steve

Hello All,

I have a situation where i want to implement 8 instance of some particular reg_file which all have many reg_def and reg_fld.

For example :
I have 8 instance of one DUT module (TEST0, TEST1,TEST2... TEST8), since its all are the instance so all the instance will have the sets of registers.. so to implement reg for one instance i can write code like..

extend vr_ad_reg_file_kind : [TEST0];
extend TEST0 vr_ad_reg_file {
keep size == 256;
};
reg_def EX_REG_TX_DATA TEST0 8’h00 {
// name : type : mask : reset value
reg_fld data : uint(bits:8) : RW : 0;
};

But now the issue is inside 1 instance i have around 256 registers, and i need to implement for all the 8 instance.... so can anyone suggest me how we can make instance for vr_ad_reg_file, otherwise i have to write same code for all the 8 instance.

Thanks

Just in time for the holidays, inside the posted tar ball is some code to solve 9x9 Sudoku puzzles with the Assertion-Driven Simulation (ADS) capability of Incisive Enterprise Verifier (IEV). Enjoy! Joerg Mueller Solutions Engineer for Team Verify

Hi all 

Good day.

Can anyone tell me whether it is possible to view the signals once it is modified from its previous values without closing the simvision window. If possible kindly let me know the command for it(Linux).

 Is it possible to view the schematic for the code written?? Kindly instruct me.

 Thanks all.

S K S 

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

i had encountered error message like this before. 

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

Hi all,

Is there any tutorial which explains the process of plotting the ISF function for a certain oscillator ?

Thank you.

Hello,

I am trying to import multiple verilog modules defined in a single file with "`define" directive in the top using Verilog In. The code below is an example of what my file contains.

When I use the settings below to import the modules into a library, it imports it correctly but completely ignores all `define directive; hence when I simulate using any of the modules below the simulator errors out requesting these variables.

My question: Is there a way to make Verilog In consider `define directives in every module cell created? 

Code to be imported by Cadence Verilog In:

--------------------------------------------------------

`timescale 1ns/1ps
`define PROP_DELAY 1.1
`define INVALID_DELAY 1.3

`define PERIOD 1.1
`define WIDTH 1.6
`define SETUP_TIME 2.0
`define HOLD_TIME 0.5
`define RECOVERY_TIME 3.0
`define REMOVAL_TIME 0.5
`define WIDTH_THD 0.0

`celldefine
module MY_FF (QN, VDD, VSS, A, B, CK);

inout VDD, VSS;
output QN;
input A, B, CK;
reg NOTIFIER;
supply1 xSN,xRN;
buf IC (clk, CK);
and IA (n1, A, B);
udp_dff_PWR I0 (n0, n1, clk, xRN, xSN, VDD, VSS, NOTIFIER);
not I2 (QN, n0);

wire ENABLE_B ;
wire ENABLE_A ;
assign ENABLE_B = (B) ? 1'b1:1'b0;
assign ENABLE_A = (A) ? 1'b1:1'b0;

specify
$setuphold(posedge CK &&& (ENABLE_B == 1'b1), posedge A,  `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$setuphold(posedge CK &&& (ENABLE_B == 1'b1), negedge A, `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$setuphold(posedge CK &&& (ENABLE_A == 1'b1), posedge B, `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$setuphold(posedge CK &&& (ENABLE_A == 1'b1), negedge B, `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$width(posedge CK,1.0,0.0,NOTIFIER);
$width(negedge CK,1.0,0.0,NOTIFIER);
if (A==1'b0 && B==1'b0)
(posedge CK => (QN:1'bx)) = (1.0, 1.0);
if (A==1'b1 && B==1'b0)
(posedge CK => (QN:1'bx)) = (1.0, 1.0);
if (B==1'b1)
(posedge CK => (QN:1'bx)) = (1.0,1.0);

endspecify

endmodule // MY_FF
`endcelldefine

`timescale 1ns/1ps
`celldefine
module MY_FF2 (QN, VDD, VSS, A, B, CK);

inout VDD, VSS;
output QN;
input A, B, CK;
reg NOTIFIER;
supply1 xSN,xRN;
buf IC (clk, CK);
and IA (n1, A, B);
udp_dff_PWR I0 (n0, n1, clk, xRN, xSN, VDD, VSS, NOTIFIER);
not I2 (QN, n0);

wire ENABLE_B ;
wire ENABLE_A ;
assign ENABLE_B = (B) ? 1'b1:1'b0;
assign ENABLE_A = (A) ? 1'b1:1'b0;

specify
$setuphold(posedge CK &&& (ENABLE_B == 1'b1), posedge A,  `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$setuphold(posedge CK &&& (ENABLE_B == 1'b1), negedge A,  `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$setuphold(posedge CK &&& (ENABLE_A == 1'b1), posedge B,  `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$setuphold(posedge CK &&& (ENABLE_A == 1'b1), negedge B,  `SETUP_TIME, `HOLD_TIME, NOTIFIER);
$width(posedge CK,1.0,0.0,NOTIFIER);
$width(negedge CK,1.0,0.0,NOTIFIER);
if (A==1'b0 && B==1'b0)
(posedge CK => (QN:1'bx)) = (1.0, 1.0);
if (A==1'b1 && B==1'b0)
(posedge CK => (QN:1'bx)) = (1.0, 1.0);
if (B==1'b1)
(posedge CK => (QN:1'bx)) = (1.0,1.0);

endspecify

endmodule // MY_FF2
`endcelldefine

--------------------------------------------------------

I am using the following Cadence versions:

MMSIM Version: 13.1.1.660.isr18

Virtuoso Version: IC6.1.8-64b.500.1

irun Version: 14.10-s039

Spectre Version: 18.1.0.421.isr9

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

Cadence Liberate Trio Characterization Suite, ARM-based Graviton Processors, and Amazon Web Services (AWS) Cloud have joined forces to cater to the High-Performance Computing, Machine Learning/Artificial Intelligence, and Big Data Analytics sectors. (read more)

Key Findings: Advantest, in mixed-signal SoC design, sees 50X speedup, 25 day test reduced to 12 hours, dramatic test coverage increase.

Trolling through the CDNLive archives, I discovered another gem. At the May 2013 CDNLive in Munich, Thomas Henkel and Henriette Ossoinig of Advantest presented a paper titled “Timing-accurate emulation of a mixed-signal SoC using Palladium XP”. Advantest makes advanced electronics test equipment. Among the semiconductor designs they create for these products is a test processor chip with over 100 million logic transistors, but also with lots of analog functions.They set out to find a way to speed up their full-chip simulations to a point where they could run the system software. To do that, they needed about a 50X speed-up. Well, they did it!

Figure 1: Advantest SoC Test Products

To skip the commentary, read Advantest's paper here. 

Problem Statement

Software is becoming a bigger part of just about every hardware product in every market today, and that includes the semiconductor test market. To achieve high product quality in the shortest amount of time, the hardware and software components need to be verified together as early in the design cycle as possible. However, the throughput of a typical software RTL simulation is not sufficient to run significant amounts of software on a design with hundreds of millions of transistors.  

Executing software on RTL models of the hardware means long runs  (“deep cycles”) that are a great fit for an emulator, but the mixed-signal content posed a new type of challenge for the Advantest team.  Emulators are designed to run digital logic. Analog is really outside of the expected use model. The Advantest team examined the pros and cons of various co-simulation and acceleration flows intended for mixed signal and did not feel that they could possibly get the performance they needed to have practical runtimes with software testbenches. They became determined to find a way to apply their Palladium XP platform to the problem.

Armed with the knowledge of the essential relationship between the analog operations and the logic and software operations, the team was able to craft models of the analog blocks using reduction techniques that accurately depicted the essence of the analog function required for hardware-software verification without the expense of a continuous time simulation engine.

The requirements boiled down to the following:

• Generation of digital signals with highly accurate and flexible timing

• Complete chip needs to run on Palladium XP platform

• Create high-resolution timing (100fs) with reasonable emulation performance, i.e. at least 50X faster than simulation on the fastest workstations

Solution Idea

The solution approach chosen was to simplify the functional model of the analog elements of the design down to generation of digital signal edges with high timing accuracy. The solution employed a fixed-frequency central clock that was used as a reference.Timing-critical analog signals used to produce accurately placed digital outputs were encoded into multi-bit representations that modeled the transition and timing behavior. A cell library was created that took the encoded signals and converted them to desired “regular signals”. 

Automation was added to the process by changing the netlisting to widen the analog signals according to user-specified schematic annotations. All of this was done in a fashion that is compatible with debugging in Cadence’s Simvision tool.  Details on all of these facets to follow.

The Timing Description Unit (TDU) Format

The innovative thinking that enabled the use of Palladium XP was the idea of combining a reference clock and quantized signal encoding to create offsets from the reference. The implementation of these ideas was done in a general manner so that different bit widths could easily be used to control the quantization accuracy.

Figure 2: Quantization method using signal encoding

Timed Cell Modeling

You might be thinking – timing and emulation, together..!?  Yes, and here’s a method to do it….

The engineering work in realizing the TDU idea involved the creation of a library of cells that could be used to compose the functions that convert the encoded signal into the “real signals” (timing-accurate digital output signals). Beyond some basic logic cells (e.g., INV, AND, OR, MUX, DFF, TFF, LATCH), some special cells such as window-latch, phase-detect, vernier-delay-line, and clock-generator were created. The converter functions were all composed from these basic cells. This approach ensured an easy path from design into emulation.

The solution was made parameterizable to handle varying needs for accuracy.  Single bit inputs need to be translated into transitions at offset zero or a high or low coding depending on the previous state.  Single bit outputs deliver the final state of the high-resolution output either at time zero, the next falling, or the next rising edge of the grid clock, selectable by parameter. Output transitions can optionally be filtered to conform to a configurable minimum pulse width.

Timed Cell Structure

There are four critical elements to the design of the conversion function blocks (time cells):

                Input conditioning – convert to zero-offset, optional glitch preservation, and multi-cycle path

                Transition sorting – sort transitions according to timing offset and specified precedence

                Function – for each input transition, create appropriate output transition

                Output filtering – Capability to optionally remove multiple transitions, zero-width, pulses, etc.

Timed Cell Caveat

All of the cells are combinational and deliver a result in the same cycle of an input transition. This holds for storage elements as well. For example a DFF will have a feedback to hold its state. Because feedback creates combinational loops, the loops need a designation to be broken (using a brk input conditioning function in this case – more on this later). This creates an additional requirement for flip-flop clock signals to be restricted to two edges per reference clock cycle.

Note that without minimum width filtering, the number of output transitions of logic gates is the sum of all input transitions (potentially lots of switching activity). Also note that the delay cell has the effect of doubling the number of output transitions per input transition.

Figure 3: Edge doubling will increase switching during execution

SimVision Debug Support

The debug process was set up to revolve around VCD file processing and directed and viewed within the SimVision debug tool. In order to understand what is going on from a functional standpoint, the raw simulation output processes the encoded signals so that they appear as high-precision timing signals in the waveform viewer. The flow is shown in the figure below.

Figure 4: Waveform post-processing flow

The result is the flow is a functional debug view that includes association across representations of the design and testbench, including those high-precision timing signals.

Figure 5: Simvision debug window setup

Overview of the Design Under Verification (DUV)

Verification has to prove that analog design works correctly together with the digital part. The critical elements to verify include:

• Programmable delay lines move data edges with sub-ps resolution

• PLL generates clocks with wide range of programmable frequency

• High-speed data stream at output of analog is correct

These goals can be achieved only if parts of the analog design are represented with fine resolution timing.

Figure 6: Mixed-signal design partitioning for verification

How to Get to a Verilog Model of the Analog Design

There was an existing Verilog cell library with basic building blocks that included:

- Gates, flip-flops, muxes, latches

- Behavioral models of programmable delay elements, PLL, loop filter, phase detector

With a traditional simulation approach, a cell-based netlist of the analog schematic is created. This netlist is integrated with the Verilog description of the digital design and can be simulated with a normal workstation. To use Palladium simulation, the (non-synthesizable) portions of the analog design that require fine resolution timing have to be replaced by digital timing representation. This modeling task is completed by using a combination of the existing Verilog cell library and the newly developed timed cells.

Loop Breaking

One of the chief characteristics of the timed cells is that they contain only combinational cells that propagate logic from inputs to outputs. Any feedback from a cell’s transitive fanout back to an input creates a combinational loop that must be broken to reach a steady state. Although the Palladium XP loop breaking algorithm works correctly, the timed cells provided a unique challenge that led to unpredictable results.  Thus, a process was developed to ensure predictable loop breaking behavior. The user input to the process was to provide a property at the loop origin that the netlister recognized and translated to the appropriate loop breaking directives.

Augmented Netlisting

Ease of use and flow automation were two primary considerations in creating a solution that could be deployed more broadly. That made creating a one-step netlisting process a high-value item. The signal point annotation and automatic hierarchy expansion of the “digital timing” parameter helped achieve that goal. The netlister was enriched to identify the key schematic annotations at any point in the hierarchy, including bit and bus signals.

Consistency checking and annotation reporting created a log useful in debugging and evolving the solution.

Wrapper Cell Modeling and Verification

The netlister generates a list of schematic instances at the designated “netlister stop level” for each instance the requires a Verilog model with fine resolution timing. For the design in this paper there were 160 such instances.

The library of timed cells was created; these cells were actually “wrapper” cells comprised of the primitives for timed cell modeling described above. A new verification flow was created that used the behavior of the primitive cells as a reference for the expected behavior of the composed cells. The testing of the composed cells included had the timing width parameter set to 1 to enable direct comparison to the primitive cells. The Cadence Incisive Enterprise Simullator tool was successfully employed to perform assertion-based verification of the composed cells versus the existing primitive cells.

Mapping and Long Paths

Initial experiments showed that inclusion of the fine resolution timed cells into the digital emulation environment would about double the required capacity per run. As previously pointed out, the timed cells having only combinational forward paths creates a loop issue. This fact also had the result of creating some such paths that were more than 5,000 steps of logic. A timed cell optimization process helped to solve this problem. The basic idea was to break the path up by adding flip-flops in strategic locations to reduce combinational path length. The reason that this is important is that the maximum achievable emulation speed is related to combinational path length.

Results

Once the flow was in place, and some realistic test cases were run through it, some further performance tuning opportunities were discovered to additionally reduce runtimes (e.g., Palladium XP tbrun mode was used to gain speed). The reference used for overall speed gains on this solution was versus a purely software-based solution on the highest performance workstation available.

The findings of the performance comparison were startlingly good:

• On Palladium XP, the simulation speed is 50X faster than on Advantest’s fastest workstation

• Software simulation running 25 days can now be run in 12 hours -> realistic runtime enables long-running tests that were not feasible before

• Now have 500 tests that execute once in more than 48 hours

• They can be run much more frequently using randomization and this will increase test coverage dramatically

Steve Carlson

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.

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