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P-Cell not enforcing parameter limits

jasons

This is my first post to a Cadence forum, so please excuse me if it's posted to the wrong board.  I am encountering a situation where transistor p-cells are not enforcing minimum and maximum requirements on parmaters such as finger number and finger width.  Instead, when an illegal combination of those values is entered, there's a quiet little message in the CIW, but the cell is instantiated just the same, with the illegal values.  A callback solves the problem if and only if "apply" has not been selected, in which case the device does not revert to a legal set of values after a callback.

The p-cells are foundary provided, and compiled.  

Anything I can do to enforce the rules?

 thanks!

 

Parents

  • Often, the pcell code does not check the constraints on a variable. The pcell draws to whatever values are assigned to the instance. The pcell code may not know the values of the constraints (min or max for example) and therefore does not do the checking.

    The CDF interfaces to the pcell. It controls what is presented to the user in the editProperty form. When a value is entered into a field in the form, and the field loses focus (cursor is moved to another field or the user presses apply or OK), any callback on the field is executed. This is where the value should be checked. The value is then available to the pcell parameter.

    Check the CDF to find out the callbacks for the offending field. Dump the CDF to a file and find the callback for the field. You said that there is a message sent to the CIW, this may be what the callback does, not changing the value to a valid value.  You will have to file a bug with the PDK supplier so that this problem is fixed.

     Ted

Reply

  • Often, the pcell code does not check the constraints on a variable. The pcell draws to whatever values are assigned to the instance. The pcell code may not know the values of the constraints (min or max for example) and therefore does not do the checking.

    The CDF interfaces to the pcell. It controls what is presented to the user in the editProperty form. When a value is entered into a field in the form, and the field loses focus (cursor is moved to another field or the user presses apply or OK), any callback on the field is executed. This is where the value should be checked. The value is then available to the pcell parameter.

    Check the CDF to find out the callbacks for the offending field. Dump the CDF to a file and find the callback for the field. You said that there is a message sent to the CIW, this may be what the callback does, not changing the value to a valid value.  You will have to file a bug with the PDK supplier so that this problem is fixed.

     Ted

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