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
Copyright 2009 Synopsys, Inc. All rights reserved.
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).
B-2008.12-SP2 Copyright (c) 2009 Synopsys, Inc. All rights reserved.
set_noise_margin -above -low 4 m9hpd_std_slow/hpd_sao21bx2/A2
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