Shielding by Route

In most cases, you will configure shields by assigning a constraint group to the net to be shielded. Space-based Router and Chip Optimizer also lets you specify unique shield settings for routes of the net, allowing you to change options, such as shield spacing or width, on specific routes by creating another constraint group and assigning it those routes. This is especially helpful when shielding cannot be added along some routes due to insufficient space. Reducing width or spacing requirements along those routes might allow them to be shielded, while keeping stricter requirements on the rest of the net. You can also use this method to create thicker shields for specific routes for signal integrity issues.

To configure a net with different shield settings on some routes,

Create a constraint group and assign it to the net to be shielded.

Create another constraint group.

create_constraint_group -name s_shieldGroupName2

Assign the constraint group from step 2 to the routes that should have shield settings that are different from the rest of the net.
One way to do this is to set the Routing Object Granularity to Entire Route, then interactively select the route, or use find_by_area to add the route to the selection set.
```
set_active -object { "route" } -active true
set_active -object { "net" "connected_shapes" } -active false
replace_set -set1 [find_by_area -single -region {f_xlo f_ylo f_xhi f_yhi}] \
  -set2 [get_selection_set]
set_constraint_group -shield s_shieldGroupName2 -set [get_selection_set]
```
Add constraints for the routes to the new constraint group as in step 3 of Configuring Shield Wires. The router will apply the appropriate constraints for the net and individual routes when adding the shield wires.

Virtuoso Space-based Router Command Reference
Product Version IC23.1, September 2023