www.eda.co.uk

This TechWatch a continuation of the second part of my Design Reuse with Altium Designer presentation from our user conference on the 31st October 2006. The final topic will be covered in the next TechWatch update. The files for this and all of the other TechWatch's in the Design Reuse series can be downloaded here (451kb). In this TechWatch we will be working with files from the 'Parametric Hierarchy files' folder.

Design Reuse methodologies can be implemented as a number of “layers”

Layer 1: Features that allow fast and “intelligent” cloning of localised circuitry.

Layer 2: Reusing entire schematic sheets and multi-channel design techniques.

Layer 3: Creation of re-usable, pre-verified, core “components” stored in libraries.

Layer 2:

Summary so far

In the last TechWatch in the series we looked at Multi-Channel Design to duplicate the same section of a design multiple times. It is worth noting that the techniques we used here work just as well when updating existing schematics.
 

Parametric Hierarchical Design

The challenge with reusing a section of design is that the values of the components are not always fixed from one design to the next. The Altium Designer feature for Parametric Hierarchical Design solves this, it allows you to move the specification of the component values from the schematic sheet, into the sheet symbol that references that them.

A good example of the use of this feature is in the design of a 10-channel graphic equaliser. Each sub sheet is for a particular frequency band and shares the same schematic document. In the RCNetwork.SchDoc (from the AudioEqualizer.PrjPCB) there is currently just a single sheet. Double clicking on a component we can see the component parameters. The value field has a value that is defined using a formula as do all the other components.

In the top level schematic (EqualizerTop.SchDoc) there are 10 sheet symbols if we view the properties for one of these we will see the parameter names and their values. Double clicking on a sheet symbol like shown below will show the Sheet Symbol dialog.

The Parameter Manager provides a useful way to browse all the parameters for the entire project. Here are all the sheet symbol parameters in the design. These columns show the various values for the components.

Doing this will compile the project so returning to the RCNetwork.SchDoc can now see that each sub sheet has been generated.

If we generate a BOM, we will see the correct component values for each channel. It is possible to change the designators in the same way as we did in the Multi-Channel Design example using Project ›› Project Options ›› Multi-Channel.

When the PCB is updated, the components will add the correct comment parameters as specified by the sheet symbols, and the formulas in the components themselves. If we were now going to take this over to PCB we could place one room of each of the 20 channels and again use the Copy Room Formats command.

Go to the next TechWatch we will be summarising Layer 2 and looking at Core Components or return to the previous TechWatch.