Calculation of Antenna Numbers for MUSTJOIN Terminals

To calculate the antenna numbers of MUSTJOIN terminals, in the Extract step, Abstract Generator identifies disjoint groups of shapes extracted for nets in the layout. It then renames these terminals and sets the MUSTJOIN attribute on these terminals.

Abstract Generator creates a separate terminal for each island. For example, for terminal A and n number of disjoint islands, the tool creates terminals A, A_mj1, A_mj2 …… A_mjn-1.

For each island, Abstract Generator sets the antenna number to its corresponding terminal name. Abstract Generator calculates the antenna values by comparing different antenna numbers for each island individually. It does not compare antenna numbers across different islands.

You can use the following options to calculate antenna numbers for disjoint islands of a MUSTJOIN terminal:

• Either set the ExtractMustJoinTerminals option to true for the all the terminals or specify the terminal name in the ExtractMustJoinTerminals option.
  

  absSetBinOption( "<Bin Name>" "ExtractMustJoinAlways" "true") OR

  absSetBinOption( "<Bin Name>" "ExtractMustJoinTerminals" "terminal_name")

• Select the Extract signal nets option on the Signal Tab in the Running step Extract form or use absSetBinOption to set the ExtractSig option to true.
  

  absSetBinOption( "<Bin Name>" "ExtractSig" "true")

• Select one of the following antenna calculation options.
  • Calculate hierarchical antenna
  • Calculate input pin antenna
  • Calculate output pin antenna
  • Calculate inout pin antenna
  • Calculate antenna metal area
  • Calculate antenna metal side area

To understand this better, consider the following example, Mxy is yth shape of Mx layer. For example, M12 is the second shape of the M1 layer.

Here, G1, G2, G3, G4, G5, and G6 represent the gate areas for the corresponding metal shapes. Cut or via layers are omitted for the sake of simplicity in the design.

When you select the Calculate antenna metal area option, Abstract Generator calculates the following values:

• ANTENNAPARTIALMETALAREA is the largest metal shape area for each layer.
• ANTENNAGATEAREA is the minimum gate area among all the gates that are visible through each metal shape.
• ANTENNAMAXAREACAR is the largest path among all the paths. It is calculated as area of metal layer divided by the area of gates visible to the shape.

The following table shows how antenna values are calculated for the above example:

Consider another example, as shown below:

The following table shows how antenna values are calculated for the above example:

Related Topics

Antenna Generation for MUSTJOIN and MUSTJOINALLPORTS Terminals

Calculation of Antenna Numbers for MUSTJOINALLPORTS Terminals

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