HIPEX-Net: Interface From Expert

1. Introduction

HIPEX-Net is a hierarchical layout extractor. It can create both hierarchical and flat SPICE formatted netlists of the extracted layout. HIPEX-Net also performs ERC (Electric Rule Checking) on the extracted netlist. This checks for connectivity errors in a chip design such as opens, shorts, and dangling nodes.

HIPEX-Net is a sophisticated script-driven tool. To invoke the extraction, the user must provide a number of input script files in LISA: Language for Interfacing Silvaco Applications. These are option file, layer mapping files, and technology file. HIPEX-Net technology is defined by a list of various LISA statements that build derived layers, connectivity, and devices. However, the input generation is easy when running HIPEX-Net from Expert.

Expert automatically creates all the input files needed by HIPEX-Net. You use the Expert GUI to define technology and the extractor settings rather than writing LISA scripts manually. You can also use Dracula technology converter Expert provides.

HIPEX-Net introduces in Expert hierarchical Node Probing feature.


2. HIPEX-Net Options Dialog Box

The user controls the extractor run-time settings in the HIPEX-Net Options dialog box. It is composed of Layout, Node names, ERC/Pins, Explosion, Ports, Output, and Netlist Technology Definition pages.

Figure 1. Layout page of the Options dialog.

2.1. Layout Settings

Here you choose which cell is to be extracted. You can specify any cell in the layout hierarchy as a top level. The Flatten Layout option makes HIPEX-Net flatten the layout before extracting the netlist. This allows you to process safely layouts with hierarchy violations (devices built partly in one cell and partly in another) at the cost of performance. The Rebuild Derived Layers checkbox should be checked if there have been any changes in the layers related to device/connectivity definition. The Annotate Layout checkbox makes the Node Probing feature available after HIPEX-Net completes the netlist extraction. Checking this box can decrease HIPEX-Net performance, but the benefit is that you can search by name or point by mouse nets, devices, and instances to highlight and traverse them directly in the layout editor window.

The two Check for ”...” options check the layout for multiple identical placements of instances and for non-45 angle geometry. The Resolution Factor text box defines the minimum distance that separates two distinct points of the layout.

Using the Write Device Labels into Layout group of options, you set up text labels that HIPEX-Net can add to devices found in the layout. The text is the SPICE statement of the device.

The Text Data Types group box contains the two text fields, Global and Port, for setting the global and port text datatypes. HIPEX-Net considers text with any other datatype as local text. Local text are labels for a node in a cell, while global text are labels for nodes for the entire layout (e.g., VSS and VDD). Port text are intended to label ports only.


2.2. Node Names Settings

HIPEX-Net extracts text from the layout and uses it to: (1) assign names to nodes in the output netlist and (2) check for opens and shorts in the layout. HIPEX-Net follows a set of rules when processing layout text for node names. For example, global text always takes precedence over local text. You can fine tune node naming in the Node Names page of the Options dialog (see Figure 2).

Figure 2. Node Names Options Page.

Here you define the separator and prefix characters HIPEX-Net uses in node names. If HIPEX-Net cannot find text anywhere in the hierarchy for a node, it creates a name for the node automatically based on the serial number. You can make HIPEX-Net add the X, Y layout local coordinates to autogenerated names by checking the appropriate box.

The two text boxes, Power Node Synonyms and Ground Node Synonyms, allow you to define the synonym names to the power and ground node. HIPEX-Net substitutes all the listed names by the first one. The Global Node Names text box lists labels you want to make global in spite of their actual datatype in the layout.

The Virtual Nets group box provides options to make HIPEX-Net consider separated virtual (unfinished) nets as the same net.


2.3. ERC/Pins Settings

HIPEX-Net uses extracted text from the layout to check continuity and reports possible shorts and opens. If HIPEX-Net finds open or shorted nodes, it flags them by writing error messages to the summary file. HIPEX-Net can also report dangle nodes that are not attached to any devices.

You control various ERC options in the ERC/Pins page of the Options dialog shown in Figure 3.

Figure 3. ERC/Pins Options Page.

Here you choose whether HIPEX-Net reports in the summary file all the dangles it encounters. Using the Output Dangles checkbox, you can dump flat layout of the dangle nodes into the separate GDSII file. The two Warning for “...” checkboxes make HIPEX-Net write in the summary file the warning messages about improperly connected MOSFETs and BJTs. The Rename Opens drop-down list determines whether HIPEX-Net assigns different names to the nodes having the same local (in a given cell) or global (in the entire layout) text label.

The Pins options determine whether HIPEX-Net ignores dangle pins of subcircuits and renames open global pins.


2.4. Explosion Settings

In the Explosion page of the Options dialog, you can define various operations on design hierarchy, such as cell explosions and ignoring particular cells during the extraction. Figure 4 shows the Explosion page.

Figure 4. Explosion Options Page.

Here you can explode all the instances of cells containing only wiring, raising their content up one level before the cell is processed. The other checkbox forces HIPEX-Net to ignore all text at lower levels of the hierarchy except the top one.

The table in the bottom of the Explosion page allows you to define operations on individual cells. The allowable operations are: EXPLODE, FLATTEN, SMASH, and IGNORE. The AUTO option means do nothing.


2.5. Ports Settings

One of the benefits using HIPEX-Net is that it doesn’t force you to declare the cell pins or assign names to cell pins. HIPEX-Net creates pins automatically when it finds any hierarchical connection (that is, between cells from different hierarchy levels). Nevertheless, HIPEX-Net allows you to predefine names and locations of cell pins. These predefined pins are called ports. There are a couple of advantages using ports. One advantage is you can define pins for the top cell in the layout. The other advantage is you can verify hierarchical connections (i.e., pins) by ports. If you do so, HIPEX-Net creates pins only in those locations where both pin and port are present.

You define ports in the Ports page of the Options dialog box (see Figure 5).

Figure 5. Ports Options Page.

Use a special port layer in your layout (you can also use several port layers if needed). Give your ports names using port datatype text. Then, set this layer as port layer using the Add Layers button. Once you define port layer(s), you can link/unlink conductor layers to the selected port layer. Then, the port-linked conductor layers can be verified for hierarchical connections that go through them. You can force HIPEX-Net to create subcircuit pins in the port locations, even if there are no actual hierarchical connections, by checking the Create Ports box.


2.6. Output Settings

In the Output page of the Options dialog, you define filenames of the output SPICE netlists and control SPICE device parameters to be written to those netlists. Figure 6 shows the Output page.

Figure 6. Output Options Page.

The two Write “...” allow you to output additional SPICE parameters for MOSFETs and capacitors.


3. Netlist Technology Definition

The Netlist Technology Definition page of the Options dialog allows you to define technology information needed by HIPEX-Net. Expert saves the user technology definitions in the project file (.eld file). Then, the layout editor converts the technology data to the HIPEX-Net technology file once you run the extractor.

HIPEX-Net deals with three types of technology information (see Figure 7): Layer Derivation Statements (Derived Layers), Connectivity Statements (Connectivity), and Device Definitions (Devices). You can modify these types of technology parameters separately.

Figure 7. Netlist Technology Definition Page.

For technology definition, you can use GUI controls and dialogs accessible from the page above. The alternative way is to load technology data from external Expert technology files (.tcn files). You can create .tcn files in any text editor manually or use the Setup>>Technology>> Import Technology”...” menu command to convert Dracula rule files.


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