Foreword
This article will follow the rules pcb design, methods, rules set records.
In addition, due to the special allegro unfriendly for the novice to learn, especially in AD users are used to, and there will be a significant difference between the first time to get started. So after we finish I will temporarily end in accordance with the pcb design process to explain the recording operation, turn to write some more basic but profound impact on operations, such as shortcut keys such. After all, I am also a beginner, encountered numerous difficulties in the first design, but also from scratch systematically stroked a stroke.
Rule Settings
allegro which rules manager called constraint manager (Constraint Manager). Open as shown below:
Set width
, The first set of signal width substantially all of the layers in the following diagram, provided 6mil.
Because of this design includes a differential line, so we need to meet the needs of the impedance matching rule is set to differential line alone. First, create a new rule here, right-click selection deafult create physical Cset, as shown in FIG. 100 Ohm differential impedance matching of needs, so here the name is set to "DIFF100", easy to understand.
Here modifications, so a line width of 4.5 mil, 8mil pitch, so that impedance is 100 ohms.
This is not a rule of differential lines to OK it?
Obviously not, do not believe themselves to paint it. As for why not, because allegro has had a so-called "constrained enable" concept, will deal with later.
Set vias
Continuing from the previous page, move to the right, you can see this column vias, setting rules for holes.
Double-VIA, the pop-up window, vias used here VIA8_F
Once you've selected can choose the right type of hole saw is moved to the right, then click OK to.
Set rules, only one size enough vias, as shown below:
Spacing settings
Interface spacing is set as shown below, where all of the first set with a minimum spacing 6mil.
The best pitch copper and other large point, thus set to 10mil, as shown below:
Enable rule
Just I said, in fact, the rules of the differential pair is not enabled, then enabling's how it goes.
First press to enter the network interface shown in Figure:
Here you can see before adding differential pairs were all here. Use the shift key to select multiple choice all differential pairs, then right-click and select create -> create net class. As shown below:
a name of a concise:
such a class is equivalent to a new (and AD of the same class), and then in the attribute fields in this class to be enabled to "DIFF_100" rule.
In summary, allegro constraints enable the present situation is all about:
1. You only need to meet this part of the basic constraints enough, it does not need to deliberately go and change, because all networks are fundamental constraint by default .
2. This part of your network requires separate rules, such as a differential pair, power networks, then you first need to create a new rule, then its enabled so that it matches the corresponding new rules on the network side manually.
