JCUI Marvell

Thursday, October 28, 2010

Fwd: 68-95-99.7 rule - Wikipedia, the free encyclopedia

Helen, Jeffrey and Stephane

408-896-8810

---------- Forwarded message ----------
From: Jeffrey CUI <huijun.cui@gmail.com>
Date: Thu, Oct 28, 2010 at 4:48 PM
Subject: 68-95-99.7 rule - Wikipedia, the free encyclopedia
To: Jeffrey CUI <huijun.cui@gmail.com>

1 sigma

2 sigma

3 sigma distribution

http://en.wikipedia.org/wiki/68-95-99.7_rule

Tuesday, October 26, 2010

Clock reconvergence pessimism removal (CRPR) 2

CRPR: is to remove the unnecessary pessimism for the common clock path for the launching and receiving registers.

The removal portion or the credit is the difference between max delay and min delay of the common portion.

There is a command called : report_crpr which could give the exact crp value. Calculate crpr is quite expensive, so report_timing won't give you the exact cpr value. The value given by the report_timing is the exact value +/- the range of "timing_crpr_threshold_ps". That is the reason that you could see different crp value between report_crpr and report_timing.

To deal with the above issue, synopsys create another variable "timing_crpr_enable_adaptive_engine" to handle, when this variable is set to true, only the path with violation will be recalculate cpr, so the cpr will be accurate.

Clock reconvergence pessimism removal (CRPR)

Clock reconvergence pessimism removal (CRPR)

In the adaptive CRPR mode, PrimeTime SI calculates CRPR only for the critical path set
(the violating portion of the design), thereby reducing the complexity of CRPR analysis. The
critical path set is the set of all paths with a slack of less than zero, for both setup and hold
timing constraints. The adaptive mode operates only when crosstalk analysis is enabled and
the maximum iteration count is set to 2 or more.

Typically, more nets are reselected for analysis in the second iteration using adaptive CRPR
because no CRPR is done in the first iteration. The resulting analysis is more accurate (less
pessimistic) because more nets are reselected for analysis.

report_timing and report_crpr

CRPR, or clock reconvergence pessimism removal, accounts for the difference in min/max delay of the portion of the clock network that is common to both the launch and the capture paths. For a path, it finds the common pin where the clock paths diverge, computes the difference between the min/max arrival times (the "CRP" value), and applies this as a credit to the path slack.

pt_shell> report_app_var *crpr*
Variable Value Type Default Constraints
----------------------- --------- ------- ---------- -----------------------
timing_crpr_enable_adaptive_engine false bool false
timing_crpr_minimize_grouping false bool false
timing_crpr_remove_clock_to_data_crp false bool false
timing_crpr_remove_muxed_clock_crp true bool true
timing_crpr_threshold_ps 1000 real 20 val >= 1

CRPR should be set to true to get things closer to the .........

Talk with Oscar ( library guy )

1. Library team will provide CCSN model for each library, sure it has corner ( fast, slow etc. ), it is cell-based and text so it is readable.

2. It doesn't make sense to use set_nose_margin, set_noise_immunity_curve, it is a coarse setting and some teams use it to add extra margin.

3. We do have lef file available ( I love lef file, I could extract lots of information from it ).

PTL, I got all the information I need.

Question: which corner we use when we analyze noise ???

Monday, October 25, 2010

set_noise_margin

-----Original Message-----
From: Jeffrey H Cui [mailto:jeffrey@marvell.com]
Sent: Monday, October 25, 2010 6:25 PM
To: Jeffrey Cui
Subject:

2. Synopsys Commands Command Reference
set_noise_margin

NAME
set_noise_margin
Sets noise margin for a library pin, port, or pin.

SYNTAX
int set_noise_margin
[-above]
[-below]
[-low]
[-high]
margin_value
object_list

float margin_value
list object_list

ARGUMENTS
-above Specifies the noise margin for above ground or power rail noise
analysis region.

-below Specifies the noise margin for below ground or power rail noise
analysis region.

-low Specifies the noise margin for ground rail noise.

-high Specifies the noise margin for power rail noise.

margin_value
Specifies a margin value. The value is the input height in
units of voltage. 1.0.

object_list
Specifies a list of lib-pins or ports.

DESCRIPTION
Each library cell input can tolerate a certain amount of noise without
causing a failure at the cell output. This characteristic is called
noise immunity. This command specifies noise immunity at library pins
to determine whether noise failures occur as well as the amount of
noise slack.

Noise immunity in the library can be specified as noise immunity
curves, polynomials, or tables or in terms of noise margins.

This command specifies a noise margin for a library pin, design port,
or pin. It can be used in the absence of library-specified noise immu-
nity characteristics, or to override the library-specified characteris-
tics by replacing them with noise margins. Noise immunity curves that
have been annotated using the set_noise_immunity_curve command will
override noise margins set by this command.

Noise margins consider only the bump heights at the cell inputs. Using
height-only noise margins is simpler, faster, and more conservative
than the other methods.

For high, narrow noise bumps, using height-only noise margins is pes-
simistic because it treats some bumps as noise failures that would oth-
erwise pass with the immunity curve model. However, for wide noise
bumps, using noise
margins gives the same results as using noise immunity curves.

Noise immunity characteristics can vary for different noise bump types,
so there can be four different noise margins associated with each
input: below low, above low, below high, and above high. All values are
specified as positive numbers for all four types of noise bumps.

In the absence of command-specified or library-specified noise immunity
data, PrimeTime SI calculates the maximum allowable noise bump heights
based on DC noise margins of the driver and receiver, as defined in the
.lib technology library by the input/output logic-level parameters.

report_noise_calculation will show whether noise margin information was
taken from the library or annotated by this command.

EXAMPLES
This example specifies a margin of 4 for above the ground rail noise
for pin A of library cell IV in the lsi_10k library:

pt_shell> set_noise_margin -above -low 4 lsi_10k/IV/A

SEE ALSO
set_noise_immunity_curve (2), report_noise_calculation (2),
remove_noise_margin (2).

set_noise_margin -above -low 4 m9hpd_std_slow/hpd_sao21bx2/A2

set_noise_immunity_curve

-----Original Message-----
From: Jeffrey H Cui [mailto:jeffrey@marvell.com]
Sent: Monday, October 25, 2010 6:25 PM
To: Jeffrey Cui
Subject:

2. Synopsys Commands Command Reference
set_noise_immunity_curve

NAME
set_noise_immunity_curve
Sets noise immunity curve for a library pin or port.

SYNTAX
int set_noise_immunity_curve
[-above]
[-below]
[-low]
[-high]
[-height height_value]
[-width width_value]
[-area area_value]
object_list

float height_value
float width_value
float area_value
list object_list

ARGUMENTS
-above Specifies an immunity curve for above ground or power rail noise
analysis region.

-below Specifies an immunity curve for below ground or power rail noise
analysis region.

-low Specifies an immunity curve for ground rail noise.

-high Specifies an immunity curve for power rail noise.

-height height_value
Specifies the height of the input voltage bump at the threshold
of logic failure. The height is in the voltage units of the
library.

-width width_value
Specifies the width of the input voltage bump at the threshold
of logic failure. The width is in the time units of the
library.

-area area_value
Specifies an area value for the curve. This parameter specifies
the size of the hyperbolic curve. 1.0.

object_list
Specifies a list of lib-pins or ports.

DESCRIPTION
Each cell input can tolerate a certain amount of noise without causing
a failure at the cell output. This characteristic is called noise immu-
nity. This command specifies noise immunity at library pins to deter-
mine whether noise failures occur as well as the amount of noise slack.

Noise immunity in the library can be specified as noise immunity
curves, polynomials, or tables or in terms of noise margins that con-
sider only the bump heights at the cell inputs.

This command specifies a noise immunity curve for a library pin or
design port. It can be used in the absence of library-specified noise
immunity characteristics, or to override the library-specified charac-
teristics by replacing them with a noise immunity curve. This command
will also override noise margins that have been annotated using the
set_noise_margin command,

The curve is hyperbolic with three coefficients to fully specify the
hyperbola: height and width of the input voltage bump at the threshold
of logic failure, and an area value to specify the size of the curve.
The three coefficients should be chosen to match the hyperbolic curve
to the data points obtained by laboratory characterization.

Noise immunity characteristics can vary for different noise bump types,
so there can be four different noise immunity curves associated with
each input: below low, above low, below high, and above high. All coef-
ficients are specified as positive numbers for all four types of noise
bumps.

report_noise_calculation will show whether noise immunity information
was taken from the library or annotated by this command.

EXAMPLES
This example specifies a noise height of 2, width of 3, area of 4 for
above the ground rail noise for pin A of library cell IV in the lsi_10k
library:

pt_shell> set_noise_immunity_curve -above -height 2 -width 3 \
-area 4 lsi_10k/IV/A

SEE ALSO
set_noise_margin (2), report_noise_calculation (2), remove_noise_immu-
nity_curve (2).

si_noise_composite_aggr_mode

NAME
   si_noise_composite_aggr_mode
   Specifies the composite aggressor mode for noise analysis.

TYPE
   String

DEFAULT
   disabled

DESCRIPTION
   This variable specifies which composite aggressor mode is used in
   PrimeTime SI noise analysis. Allowed values are disabled (the
   default), which turns off the composite aggressor feature. normal,
   causes PrimeTime SI to calculate noise by utilizing the non-statistical
   composite aggressor feature. Selecting statistical causes PrimeTime SI
   to calculate noise by using the statistical composite aggressor flow.

   In disabled composite aggressor mode, PrimeTime SI uses its original
   flow with composite aggressor completely off to analyze the noise.

   In normal composite aggressor mode, PrimeTime SI aggregates the effect
   of multiple small aggressors into a single composite aggressor, thereby
   reducing the computational complexity and improving the performance.

   statistical composite aggressor mode reduces the pessimism for noise
   analysis by reducing the effect of composite aggressor.

   For the current value of this variable, type printvar si_noise_compos-
   ite_aggr_mode.