abutFunction Property

abutFunction string t_function_name

Description

Specifies a user-defined callback to process abutment and unabutment.

The value of this property is the name of a user-defined Cadence® SKILL function to be executed before abutment takes place. Auto-abutment passes this function the following eight arguments.

1. The database ID of the cell to be abutted
2. The database ID of the cell to be abutted to
3. The database ID of the pin figure to be abutted
4. The database ID of the pin to be abutted to

If an instance is deleted, the arguments 3 and 4 above are set to nil.

1. An integer to indicate the abutment access direction of the pin being abutted where
   • 1 = top
   • 2 = bottom
   • 4 = left
   • 8 = right
2. An integer to indicate the connection condition where
   • 1 = pins are connected to the same net and do not connect to any other pin
   • 2 = pins are connected to the same net and the net connects to other pins
   • 3 = pins are connected to different nets. Used for nets that are not connected, so that structures like guard rings and wells can be adjusted appropriately.
3. An integer specifying the auto-abutment event where
   • 1 = abutFunction must compute and return abutment offset (in the direction of abutment)
   • 2 = abutFunction must adjust Pcell parameters for abutment. This is called before the offset event.
   • 3 = abutFunction must adjust Pcell parameters for unabutment
   • 4 = abutFunction must compute and return spacing offset for non abutment.
   • 5 = abutFunction must compute and update the parameters of each named abutment shape in the Pcell instance, if required, before the abutment engine computes the connection condition value to be passed to Event 2.
     
     If both the Pcell instances to be abutted support abutment Event 5, the Event 5 is executed before Event 2. If either of the instances do not support Event 5, abutment Event 5 is canceled, and the abutment of dummy shapes fails. For more information Event 5, see Abutment Event 5.
4. A database group ID (dbGroupId) of the abutment group, which is used in Event 2 and 3. The group ID is used to store information so that during unabutment, pins are returned to their original state. It is a well-accepted method to use the group attribute of a cell to hold original parameter values prior to modification by abutment.
   abutFunction returns different values for different auto-abutment events.
   • For Event 1, the function returns a floating-point number representing the offset needed to abut the cells in the direction of abutment.
     If it returns two floating-point numbers, the second number is the distance in user units that the abutting cell is moved in the direction perpendicular to the direction of abutment.
   • For Event 2, the function must return a value of true to allow abutment and nil to block abutment. When it returns nil, it must not change any parameters in any way, including setting them to new values and then resetting them to the original values.
   • For Event 3, the function can return anything; the value returned is not used.
   • For Event 4, the function returns the value of the spacing property set on non-abutting instances that determines how much the instances need to move to return to their pre-abutment state. If the spacing property is not set, the instances do not need to move.
   • For Event 5, the function must return a pair of figIDs to identify the shapes that need to be abutted. If it returns nil, the abutment of dummy shapes fails and Event 2 is called instead. For more information about Event 5, see Abutment Event 5.

Below is an example of an abutFunction.

procedure( abutFunction(iA iB pA pB pASide connection event @optional
   (group nil)) prog((result)
      case(event

           )

       (1  ; Compute offset
           result = getAbutmentOffset(iA iB pA pB pASide connection)
           )
       (2  ; Adjust Pcell parameters
           result = setAbutmentParams(iA iB pA pB pASide connection
               group)
           )
       (3  ; Adjust Pcell parameters back to default 
           resetAbutmentParams(group iA iB)
              result = t
           )
       (4  ; To get the spacing offset when pins are on different nets
           if(instA~>w > 3.0 && instB~>w > 3.0
           then
               result = 3
           else
               result = 1
           )
       (5  ; Get abut shape IDs and update Pcell parameters to remove or adjust dummy shapes
           result = myGetInterfaceShapePairFn(iA iB pA pB)
);; end of case 5
          (t  ; Anything else return a nil
               result = nil
          )
      )
      return(result)
   )
 )
 

If each pin being abutted has a different abutFunction defined, auto-abutment calls only the function defined by the pin in the cell being moved.

Example

dbReplaceProp(obj "abutFunction" "string" "mosAbutFunc")

Related Topics

abutAccessDir Property

abutClass Property

abutCondInclusion Property

abutGateNet Property

abutMosStretchMat Property

abutStretchMat Property

abutOffset Property

Device Abutment

Creating CMOS Pcells to Use with Abutment

Setting Layout XL Properties

Layout XL Properties