nearFarPercentage

Specifies the percentage of the entire net around the output pins that must be routed using the default or implicit constraint group, while the rest of the net is routed using the nearfarend constraint group. The constraint does not apply to power or ground nets, or to nets with no input pins. The constraint applies only to the output pins of the net. If the net has multiple output pins, then the rule applies to each of them.

The minimum distance between each output pin and its farthest input pin is calculated and the minimum of these is the radius of the net. The nearFarEndDistance is calculated by multiplying the nearFarPercentage by the radius, then dividing by 100. The default or implicit constraint group applies to the routing within nearFarEndDistance of each output pin (near-end region) and the nearfarend constraint group applies to the net outside the near-end region.

The nearfarend constraint group is recognized only by the global router and can contain the following constraints: validRoutingLayers, validRoutingVias, minWidth, minSpacing, and minNumCut.

nearFarPercentage Quick Reference

Constraint Type	Simple
Value Types	IntValue
Database Types	Design, Technology
Scope	design, foundry
Category	Routing
OpenAccess API	custom

Value Type

IntValue

Specifies the percentage of the entire net from the output pins that must be global routed using the default or implicit constraint group, with the rest of the net routed using the nearfarend constraint group. Valid values are 0 to 100. Tapers for the input and output pins override the nearfarend constraint group within their respective taper halos, except when the nearFarPercentage value is 0. For this case, the nearfarend constraint group will be used for the entire net. A value of 100 means that no calculation for the near-end region is needed because it will not apply for the net.

Examples

Creates a near-end region around the output pins of the nets in the selected set that is 55% of the minimum distance between the output pins and their farthest input pins, then global routes the nets. Within the near-end regions, the default or implicit constraint group for the net applies; outside that region, the nearFarEnd constraint group applies. If the default constraint group specifies layers with 4X width wires, and layers E2 and E3 specify 2X wires, then this example effectively routes the selected nets on 4X wires for 55% of the distance from the output pins and 2X wires for rest of the distance to the input pins.

create_constraint_group -name nearfar
set_constraint -constraint nearFarPercentage -IntValue 55 group nearfar
set_constraint -consraint validRoutingLayers -LayerArrayValue {E2 E3} -hardness soft -group nearfar
set_constraint_group -set[get_selection_set] -nearfarend nearfar
deselect
global_route

Related Topics

Routing Constraints

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