( ESNUG 354 Item 3 ) ---------------------------------------------- [6/1/00]
From: [ A Synopsys PhysOpt CAE ]
Subject: Overriding Computed Steiner Routing In PhysOpt & Design Compiler
John, please post this to ESNUG.
Some of my customers are asking me how to override the PhysOpt computed
Steiner routing for back-annotated nets. Steiner back annotation can be
removed with the "remove_annotated_delay" & set_annotated_delay" commands.
In the example circuit:
+-----+
A| G | +-----+
------+ A |Z A| G |
B| T +---netB----+ A |Z
------+ E | B| T +---netC-------
| 1 | -----+ E |
+-----+ | 2 |
+-----+
You can change the delay on netB to 0.25 ns with the following commands:
remove_annotated_delay -from [get_pins GATE1/Z] -to [get_pins GATE2/A]
set_annotated_delay 0.25 -from [get_pins GATE1/Z] -to [get_pins GATE2/A]
WARNING: PhysOpt & Design Compiler will not override the existing delay
value applied on a net if the new value is smaller than the previous value!
No warning is issued when one attempts to override smaller delay value on a
net, the command will be ignored. Therefore, it is ALWAYS best to remove
the annotated delay before attempting to override the delay with the
set_annotated_delay command.
- [ A Synopsys PhysOpt CAE ]
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