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

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?

The Cadence® Genus  Synthesis Solution, Innovus  Implementation System, and Tempus  Timing Signoff Solution have a lot of shared functionality, but in the past, the separate legacy user interfaces (UIs) created a lot of differences.

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Related Resources

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Do you want to create designs that are correct by construction? Read along this blog to understand how you can achieve this by using Width Spacing Patterns (WSPs) in your designs. WSPs, are track lines that provide guidance for quickly creating wires. Defining WSPs that capture the width-dependent spacing rules, and snapping the pathSegs of a wire to them, ensures that the wires meet width-dependent spacing rules.(read more)

This blog discusses key features of concurrently editing a hierarchical cellview.(read more)

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