shield_net
shield_net
{-net {s_netName…} | -set d_setObj}
-shield_net s_netName
[ -routes [ true | false ] ]
[ -shield_net_alternate s_netName ]
[ -silent [ true | false ] ]
[ -type {parallel | tandem | coaxial | tandem_split} ]
Description
Assigns a shield net to a signal net, and optionally excludes shielding on specific layers by setting constraints. This command flags the signal nets for which the router must reserve additional clearance. By default, the shields will be parallel, unless a specific type is given.
You can choose to use two different nets as parallel shields (-shield_net_alternate), for example, power and ground. In this case, one parallel shield will be power and the other will be ground. When two nets are used for parallel shields, you cannot use the existing shapes for shielding or shield sharing. To control the position of the shield nets, use add_shield_wires -alternate_tie.
Before you run this command, you must set the constraints needed for shielding. For more information on this procedure, refer to
When this command is run, a composite net comprising the signal net and the shield net is created.
A warning message is issued by this command if the taper constraint group assigned to the net is the same as the net’s default constraint group.
shielded <netName> has the same default and taper constraint groups.
If this condition exists, tapering will not be performed. If routing fails, you can change the name of either the taper or the default constraint group and re-route. For example, if both constraint groups are defaulting to the LEFDefaultRouteSpec, use this procedure:
create_constraint_group -name temp_spec -transient true
set_constraint_group -shields_shieldCG-default temp_spec -nets_netName
Because the taper and default constraint group names are now different, the tapering software will be enabled.
Use
Arguments
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When set to |
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Specifies the name of the net to use for shielding. For dual net parallel shields, this net is used for one of the shields and the net given by - |
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Specifies the second net for dual net parallel shields.
When you set this argument, you cannot share shields ( set_use_existing_shapes_for_shielding -share false |
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Specifies the type of shield to create for the given signal nets.
You can also set the shield type by setting the |
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Both tandem and parallel shields to surround the signal wire on four sides |
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Shield wires on a given layer above and below the signal wire |
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Coaxial shields with tandem shields above and below the parallel shields |
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Examples
The following command flags net2 for parallel shielding by the GND net. The shield wires will be added when the add_shield_wires command is issued.
shield_net -net net2 -shield_net GND
Related Topics
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