Calculation of Antenna Numbers for MUSTJOINALLPORTS Terminals

To calculate the antenna numbers of MUSTJOINALLPORTS terminals, in the Extract step, Abstract Generator extracts multiple disjoint islands of connected shapes for a single terminal. Antenna calculation is done after combining all the islands into a single island using a metal layer.

Abstract Generator creates a single terminal and puts all the shapes from all the islands under the terminal. A single placeholder terminal is created for antenna values of all the disjoint islands.

The router uses the metal layers to connect all the disjoint islands of the terminal from outside the MACRO block. If among all the disjoint islands of the terminal Mtop is the top-most metal layer, then router uses Mtop+1 metal layer to connect all the islands by dropping corresponding vias. If Mtop is the top-most metal layer in the technology, then router uses Mtop metal layer to connect all the islands.

As the routing operation is performed after abstract generation, Abstract Generator assumes that router will use pseudo or dummy metal shapes with zero area to connect all the islands.

For pseudo metal shapes and corresponding layers, Abstract Generator calculates the following:

• ANTENNAGATEAREA
• ANTENNADIFFAREA
• ANTENNADIFFWIDTH
• ANTENNACREDITS
• ANTENNAMAXAREACAR

During calculation of ANTENNAMAXAREACAR, Abstract Generator excludes the area of the pseudo shapes.

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

• For MUSTJOINALLPORTS terminals, do one of the following:
  • Set the ExtractMustConnectAllPins option to true for the all the terminals
  • Specify the terminal name in the ExtractMustConnectAllPinsTerminals option.
    absSetBinOption( "<Bin Name>" "ExtractMustConnectAllPinsAlways" "true") OR
absSetBinOption( "<Bin Name>" "ExtractMustConnectAllPinsTerminals" "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 establish a better understanding of how this functionality operates, consider the following example, where terminal A contains three disjoint islands of metal shapes. During antenna calculation, three disjoint set of islands will generate three sets of antenna numbers but OpenAccess terminology allows only a single placeholder terminal that contains all the islands to calculate the antenna area.

M11 represents the first metal shape of M1 layer.

M12 represents the second metal shape of M1 layer.

M21 represents the first metal shape of M2 layer.

M22 represents the second metal shape of M2 layer.

M31 represents the first metal shape of M3 layer.

M32 represents the second metal shape of M3 layer.

G1, G2, G3, G4, G5, and G6 represents the gate areas for corresponding metal shapes.

Abstract Generator adds dummy nodes at the Mtop metal layer with zero area to connect all the islands. Here, the highest metal layer is M3, and the tool adds M4 dummy layer to connect all the islands. The following image represents the combined islands.

When you select the Calculate antenna metal area option, Abstract Generator calculates ANTENNAPARTIALMETALAREA, ANTENNAGATEAREA, and ANTENNAMAXAREACAR.

• ANTENNAPARTIALMETALAREA represents the largest metal shape area for each layer.
• ANTENNAGATEAREA represents the minimum gate area among all the gates that are visible through each metal shape.
• ANTENNAMAXAREACAR represents 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 antenna calculation value is calculated for all the layers above the lowest metal layer on which the pin is present.

ANTENNAPARTIALMETALAREA	ANTENNAGATEAREA	ANTENNAMAXAREACAR
M1:max(M11,M12,M13,M14,M15,M16) M2:max(M21,M22,M23) M3:max(M31,M32,M33) M4:0	M1:min(G1,G2,G3,G4,G5,G6) M2:min(G1+G2,G3+G4,G5+G6) M3:min(G1+G2, G3+G4,G5+G6) M4:G1+G2+G3+G4+G5+G6	M1:max(M11/G1,M12/G2,M13/G3,M14/G4,M15/G5,M16/G6) M2:max(M21/(G1+G2) + PAR M1, M22/(G3+G4) + PAR M1, M23/(G5+G6)) + PAR M1 M3:max(M31/(G1+G2) + M21/(G1+G2) + max(M11/G1+ M12/G2), M32/(G3+G4) + M22/(G3+G4) + max(M13/G3+ M14/G4), M33/(G5+G6)+ M23/(G5+G6)) + max(M15/G5+ M16/G6)) M4:CAR of M3

Consider another example in which terminal A contains three asymmetric islands. The first two islands contain metal layers combined with all the nets but the third island contains only one single metal layer.

Abstract Generator needs to connect all the islands but as per the connectivity, but M15 cannot be directly connected to M32 or M31, but M15 can be connected to Metal2 and Metal3 through dummy shapes.

Abstract Generator makes all the islands appear identical by adding M2 and M3 dummy shapes to connect the third island. Once the topmost layer of all islands is same and all the islands become identical, the tool adds a new dummy shape Mtop+1 metal layer, that is M4 to connect all the disjoint islands and performs antenna calculation accordingly.

When the same top-most layer is added to all the islands, the islands become identical and the tool adds a new dummy shape Mtop+1 metal layer, M4 to connect all the disjoint islands and performs the antenna calculation accordingly.

The following image represents combined islands.

When you select the Calculate antenna metal area option, Abstract Generator calculates ANTENNAPARTIALMETALAREA, ANTENNAGATEAREA, and ANTENNAMAXAREACAR. This value is calculated for all the layers above the lowest metal layer on which the pin is present.

ANTENNAPARTIALMETALAREA	ANTENNAGATEAREA	ANTENNAMAXAREACAR
M1:max(M11,M12,M13,M14,M15) M2: max(M21,M22) M3: max(M31,M32) M4: NA	M1:min(G1,G2,G3,G4,G5) M2: min(G1+G2,G3+G4) M3: min(G1+G2, G3+G4, G5) M4: G1+G2+G3+G4+G5	M1: max(M11/G1,M12/G2,M13/G3,M14/G4,M15/G5) M2: max(M21/(G1+G2) + PAR M1,M22/G3+G4 + PAR M1) M3: max(M31/(G1+G2) + M21/(G1+G2) + max(M11/G1+ M12/G2) M32/(G3+G4) + M22/(G3+G4) + max(M13/G3+ M14/G4)) M4: CAR of M3

Related Topics

Antenna Generation for MUSTJOIN and MUSTJOINALLPORTS Terminals

Calculation of Antenna Numbers for MUSTJOIN Terminals

Antenna Calculation by Abstract Generator

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