The different types of rules are defined in the Technology Rules pages. These are divided into the DFM/DFT section and the more advanced High Speed section. Each type of rule defines parameters which are used by a particular part of the system: either to drive functionality to achieve the desired result; or to drive Design Rule Checking to detect potential errors.
In general terms, rules consist of a set of match criteria, followed by a set of values which are used on the matched design items. The rules are presented in a grid, usually one row for each rule. The rules are considered in order (top to bottom in the grid), until the first matching rule is found. It is therefore important to define the rules in the right order, with the most specific rules first, and often a ‘catch all’ rule at the bottom.
By careful use of the match criteria, you can minimise the number of rules you need to define to achieve the required result.
You can add your own notes to rules, for example your name and the date the rule was added, or why a rule has been disabled.
General information on how to use Technology pages is here
Shortcuts
Menu: Setup
Default Keys: T
Command: Technology
What is a rule?
Rules are the mechanism used to assign a set of values to a set of design items. A rule has match criteria, the basic match is an Attribute Name and a wildcard Match Value. Some types of rule can also be Layer or Area specific.
What can a rule be assigned to?
Most rules can be assigned to any Net, Signal Path, Sub Net or Differential Pair. Rules can also be assigned to Nets indirectly using a Net Class. These are the design items defined in the Nets section of the Technology dialog. In some cases, rules can be assigned to individual pins. These items can be matched by name, or by a user defined attribute.
Some rules can also be assigned on specific layers or within specific areas only.
All the above items have Rules and Attributes tabs on their page. The Rules tab provides a summary of the rules which match the selected item. The Attributes tab gives a list and means of editing the user defined attributes assigned to the item.
How are rules matched?
Rules are matched in strict order, from top to bottom in the grid.
The basic match criteria are an Attribute Name and Match Value pair. There are system defined attribute names for
Wildcards are fundamental to the match process. Wildcards can
appear in the Match Value as well as the Layer Name or Area Name match criteria. In many places a
Wildcard Wizard (available through the wizard button
) enables you to compose the wildcard string using more familiar
defining phrases (such as Contains).
The Match Value * will match any value. So a rule with Attribute Name
As rules are matched in order, the most specific rules should be before less specific rules in the grid, otherwise some rules would never be reached.
When a rule can be matched by layer, you can specify the layer side (such as Top or Outer), or the layer name (a specific name, or a wildcard match).
When creating area specific rules, the area name is used (or a wildcard match on the name) - more information on rules by area is here.
Where are rules defined?
All rules appear in the appropriate rules page of the Technology Dialog. In some cases the rules also appear in the item grid. For Differential Pairs, the matching Differential Pair Skew Rule and Differential Pair Gap Rule will appear in the Differential Pairs grid. Matching Track Length Rules and Track Length Match Rules will appear in the Net, Net Class, Signal Path or Sub Net grids. Where multiple rules may apply (because there are other criteria), it is not possible to show them all in these grids.
Disabling Rules
Uncheck the box in the Enable column to disable a rule. A disabled rule will not be used. All types of rules can be disabled, including Net Styles and Match Pair Spacing Rules.
Adding Notes to Rules
You can add your own notes to a rule by selecting its row in the grid and from the context menu choose Notes. If a rule has notes a small green triangle appears at the top right corner of its Enable cell. Hovering over the Enable cell will show the notes in a pop-up window. Use Notes again from the context menu to edit or remove a note.
Notification of Rule Errors
The small Triangle on the top left of the first cell in each row now indicates the rule state once it has been visited. Red is Error, Blue is Warning, Orange is for a new row and Grey indicates a modified row. A Green top right triangle indicates the rule contains a note. Hovering over the triangle cell will show the Error or Warning message in a pop-up window (after its notes if it has any). For example if a rule has no match string defined, or is a duplicate of another rule.
Related Topics
Differential Pair | Match Pair Spacing Rules | Net Name | Net Class | Net Styles | Signal Path | Sub Net | Technology Pages | Wildcards