Rules and Constraints

Evaluation

of Rules on Bundle Regions

A rule on a bundle region has a higher priority than a rule of the same type on the bundle. There are various considerations depending on the rule type.

You can divide evaluations of rules on bundle regions into two categories:

The bundle region rules are collected and evaluated along with the rules on the bundle hierarchy to which the bundle region belongs.
The bundle region rules are collected and evaluated directly as well as with the rules on the bundle hierarchy and the position of objects (bundle end nodes, splices) in relation to the bundle regions is significant for the evaluation results.

Considerations by Rule Types

Route by Property If the bundle hierarchy has a Don't Route rule and the region has either a Don't Route or Do Route rule, the False Overwrites True rule resolver is used in a simple hierarchical evaluation and the route cannot finish at the bundle. If the bundle hierarchy has a Do Route rule and the bundle region has a Do Route rule, a simple hierarchical evaluation is performed and it allows routing at the bundle. If the bundle hierarchy has a Do Route rule and the region has a Don't Route rule, normally the route cannot finish at the bundle because the region blocks the wire path when a simple hierarchical evaluation is performed. However, if there is a condition as follows:

Then, if necessary, it should be possible to allow finishing the partial route as follows:

Max Wires per Splice The region hierarchy rules are evaluated at the splice location. At each level in the hierarchy, the rule with the minimum value wins and controls the number of wires allowed on the splice. The router does not look up further on the bundle hierarchy because it uses the First Match Wins rule resolver. If the rule on the region states that the region cannot have any splices and the router must determine a splice location on the bundle, the router skips the region and searches for other locations along the bundle. Similarly, if the rule on the region states that no more wires can connect to the splice inside the region, then any splices outside of the region are scanned for a possible route.
Cost of Wire per Unit Length If there are rules on regions along the wire path, the rule with the maximum value wins and controls the cost. The router does not examine other levels of the object hierarchy because it uses the First Match Wins rule resolver. If there are no region rules, then the bundle hierarchy rules of the wire path are evaluated. For example:

In this case, the wire cost for wires connecting SP1 and SP2 and connecting SP2 and P2 is the value from the region rule. The wire cost for wires connecting P1 and SP1 is the value from the bundle rule. When the router is determining a splice location on the bundle and scans in this region, the router compares the route cost for this formation with the route cost for a formation where the splice stays outside of the region. This is because moving a splice into the region may result in a greater number of wires.

Cost of Splice The region hierarchy rules are evaluated at the splice location. At each level in the hierarchy, the rule with the maximum value wins and controls the cost. The router does not look up further on the bundle hierarchy because it uses the First Match Wins rule resolver. When the router determines a splice location on the bundle and scans this region, the router compares the route cost for a splice in the region against the route cost for a splice outside the region.
Minimum Splice Separation The region hierarchy rules are evaluated at the splice location. At each level in the hierarchy, the rule with the maximum value wins and controls the distance. The router does not look up further on the bundle hierarchy because it uses the First Match Wins rule resolver. When the router determines a splice location in the region and uses a region rule to control the splice separation, the router ensures that there is the minimum allowed distance between any splices regardless of whether they are inside or outside the region.
Wire Part Specification If there are region rules along the wire path, prioritized pattern matching is used to find applicable rules. Regardless of whether a valid result is found, the router does not look up further on the bundle hierarchy because it uses the First Match Wins rule resolver. Note Max Wires per Multiterm and Terminal Type Specification rules are not applied to bundle regions.

Parent Topic:

Rules and Constraints