Schematic Editors:Additional Graphical Objects.

Additional Graphical Objects

Some editors provide placement of further graphi- cal objects such as vector graphic elements (lines, circles, rectangles, arrows, etc.) or bitmaps for documentation purposes.

Structure and Organization of Graphical Designs

The basic structure of a graphical design is a page or sheet surrounded by a border and containing a title block. The user has the optional choice of the page size. The decision for a certain size depends on the design size and the printing or plotting pos- sibilities. Figure 3.7 demonstrates possible settings of PSPICE.

Symbolic Design Entry-0019

In order to keep the overview of large designs, two mechanisms are supported:

• Multi-Page Designs; and

• Hierarchical Designs.

Multi-Page Designs

Multi-page designs are usually organized by de- sign managers, i.e., programs that keep record of all documents and files belonging to one design. Off-page symbols define the interface signals be- tween all pages that constitute an extended design.

Signals connect by name and establish a single electrical node over multiple pages as long as they are connected to off-page symbols. Figure 3.8 displays two different methods of handling off- page symbols. The instance names must be unique for one level of hierarchy even if it extends over several pages.

Symbolic Design Entry-0020

Hierarchical Designs

The characteristic of hierarchical designs is the as- signment of sub-designs or sub-modules to a block symbol. Such a block symbol may be instanced any number of times on higher hierarchy level (but of course not recursively). The sub-design may contain primitive symbols as well as other block symbols. The lowest hierarchy level consists only of primitives. Resolving the hierarchy (flattening) thus leads to a flat structural netlist containing solely primitive elements. Each element of the flat netlist represents a different distinguishable object for either simulation or physical implementation. In principle the sub-designs build up a tree struc- ture (see fig. 3.9). The schematic representation of each level is usually stored as a separate file.

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