Make Cell Pin Creation

By default, Layout XL creates pins for new made cells. However, whether a pin is created for a net depends on the following criteria:

• If the nets are external to the new made cell and they do not already have pins created, Layout XL creates new pins for the nets.
  • Strongly connected pins are created for shapes and vias that have the highest metal layer, which means multiple pinFigs can have a single pin created.
• If the masters of instances in the new made cell do not already have pins created for their terminals in the made cell, Layout XL promotes pins from the masters of these instances.
  • Shapes on the highest metal layer are promoted as pinFigs.

If the design has a Fluid Guard Ring (FGR) associated with the made cell, Layout XL promotes the pin shapes from the master if the maskLayer of the pin shapes is higher than or equal to that of the FGR.

For situations that a pin needs to be promoted, the layer purpose pair (LPP) is determined based on the following:

• If the initIOPinPurposeNames environment variable is set, the Make Cell command checks if the pin purpose can make a valid LPP for pin promotion and uses it, if found valid.
• If the initIOPinPurposeNames environment variable is not set, and a purpose other than pin or drawing is specified, a valid layer with its purpose defined as pin is used, if available. If a valid layer with pin purpose does not exist, a valid layer with purpose defined as drawing is used.
• If the initIOPinPurposeNames environment variable is not set and the purpose of the original pinFig is either pin or drawing, the purpose of the pin is not changed during promotion.

Examples

Let us now consider a few design scenarios to see how Layout XL handles pin creation for made cells that have a single external net and multiple internal nets. Let us assume that:

• NMO and PMO have m=3
• net A is connected to instTerm G, making six points of connection
  
  

Scenario 1: Net A has no internal routing in the made cell

In this scenario, Layout XL creates pins for all the instance terminals connected to net A, making six connection points, as shown in the figure below.

By creating pins for all the instance terminals, Layout XL gives you the flexibility to choose the instance terminal with which to connect. In addition, it gives you a clear picture of the opens from the top level, although it correctly reports only a single open. Therefore, when you route a pin A from the top level to one of the pins in the made cell, A, Layout XL marks the top level net, net A, as complete.

If you descend into the transparent hierarchy, the Navigator assistant displays the correct net status and selecting the net highlights the nets that need to be routed inside the made cell.

Scenario 2: Net O is connected to all the four connection points inside the made cell

In this scenario, Layout XL creates pins for all the shapes on the highest level metal to increase the routability at the next level. As shown in the figure below, net O selected at the top level has only one pin in the made cell, although it has multiple pinFigs.

Related Topics

Fluid Guard Ring

initIOPinPurposeNames

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