Expert: Recent Improvements in Hierarchical Layout Inspection


The functionality of several features of Expert layout editor enhanced to deal with hierarchical layouts in more convenient ways.

1. Edit in Place

The Hierarchy>>EIP>>Direct Pick command allows you to pick an object for editing in place anywhere in cell hierarchy. To facilitate the choosing of the required object, preselection highlighting is used.

The hierarchy depth at which an object can be picked is naturally defined by the viewing depth (as defined by commands from the View>>Cell view submenu). If a primitive object (shape or text) is picked, then you will edit the cell that contains this object. If a cell instance/array is picked, then you will edit in place the cell of this instance.


2. Pick Layer

The Tools>>Pick Layer command now allows you to pick the layer (i.e., make this layer active) from a shape anywhere in cell hierarchy. This tool uses preselection-type highlighting of objects to be picked. As a by-product, one may use this tool to inspect objects deep in hierarchy: the message line shows a brief description of the object, like in the case of an ordinary preselection.


3. Node Probing

The function Verification>>Node Probing of Expert/ ExpertViews is redesigned to trace electrically connected nodes throughout the hierarchy of a cell, unlike flat-mode operation of previous versions.

In addition, this feature provides an easy and convenient way to analyze the results of Connectivity/ Netlist extraction directly on the original hierarchical design and to make necessary corrections in the design. This tool makes it possible to search and inspect nodes listed in the extracted netlist file directly in the original layout.

When the menu command Verification>> Node Probing>>Pick Node is selected, the cursor assumes the node probing shape. It is necessary to point and click at the geometric object whose electric connections or device description are to be traced. As a result, the whole net electrically connected to the probed object or device shape will be highlighted (Figure 1), and you may inspect it using other commands from Verification>>Node Probing submenu. The corresponding commands can also be executed from the Node Probing bar. (This bar may be turned on/off by View>>Control Bars command.)

Figure 1. Electrical node highlighted.


To facilitate the picking of the required object in the layout, preselection highlighting is used. In addition, it is often convenient to hide some layers for better selectivity. For example, one may show only device definition layers to pick from. After an object is picked, the node probing function ignores layer visibility.

Verification>>Node Probing>>Object Descriptors menu command shows the Connectivity/Netlist Description Tag that covers the last probed node and contains information about Net/Device and the origin of the current shape in the original design (Figure 2).

Figure 2. Object Descriptor for shape in probed node .


There are commands to highlight the consecutive shapes of the node such as First Object, Previous Object, Next Object, Last Object They are useful for consecutive node browsing.

For a more detailed inspection, there are such functions as Zoom to Node (Figure 3), View in Place (Figure 4) and View in Cell (Figure 7).

Figure 3. Zoom to Node.


Figure 4. View in Place.


It is possible to save the highlighted node into a new cell for later inspection or for historic references (Figure 5). The command Verification>>Node Probing>>Copy Node to New Cell copies all geometry in flat form to a newly created cell.

Figure 5. Copy Node to New Cell


One more function Verification>>Node Search is added into menu and duplicated in the Search Net/Device Bar, used for searching the nets or devices by their name. There is an edit field on the Search Net/Device Bar for typing the name of the net/device to be found and highlighted in response to Find Device command (Figure 6). The full Spice statement for the found device will be shown in the Edit Net/Device Name field.

Figure 6. Find Device by Name


Another important function mentioned above is viewing the highlighted object in the cell where this objected is allocated in design hierarchy. The result of this operation for a device shown in Figure 6 is represented in Figure 7.

Figure 7. View in Cell.