Altera SDC and TimeQuest API User Manual

Page 69

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Chapter 2: SDC and TimeQuest API Package and Commands

2–59

sdc_ext

Altera Corporation

Use the -include and -exclude options to include or exclude one or more of the following: register micro
parameters (utsu, uth, utco), clock arrival times (from_clock, to_clock), clock uncertainty
(clock_uncertainty) and input and output delays (input_delay, output_delay). By default, max skew
analysis includes data arrival times, clock arrival times, register micro parameters and clock uncertainty.
When -include is used, those in the inclusion list will be added to the default analysis. Similarly, when
-exclude is used, those in the exclusion list will be excluded from the default analysis. When both the
-include and -exclude options specify the same parameter, that parameter will be excluded.

When this constraint is used, results of max skew analysis are displayed in the Report Max Skew
(report_max_skew) report from the TimeQuest Timing Analyzer. Since skew is defined between two or
more paths, no results are displayed if the -from/-from_clock and -to/-to_clock filters satisfy less than two
paths.

The Fitter does not include set_max_skew constraints in design optimization. Use placement, routing, or
other timing constraints to drive the fitter to meet any set_max_skew constraints.

Example

# Constrain the skew on an input port to all registers it feeds
set_max_skew -from [get_ports din] 0.200

# Constrain the skew on output bus dout[*]
set_max_skew -to [get_ports dout\[*\]] 0.200

# Create a max skew constraint that includes only data path arrival
set_max_skew -from [get_keepers inst1|*] -to [get_keepers inst2|*] 0.200 \
\
-exclude { from_clock to_clock clock_uncertainty }

# Create a max skew constraint that includes input and output delays
# as well as the default data arrivals, clock arrivals and clock
# uncertainty
set_max_skew -from [get_keepers inst1|*] -to [get_keepers inst2|*] 0.200 \
\
-include { input_delay output_delay }

# Report the results of max skew assignments
report_max_skew -panel_name "Report Max Skew" -npaths 10 -detail \
path_only

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