Special Problem with pcell evaluation

[Guenther Sohler]

Hallo, I am trying code a pcell with a special functionality.

It works like this:

* user changes pcell properties
* pcell code is evaluated, values are calculated, shapes are drawn,

but NOW: The pcell code should be able to store some calculated values
in the pcell instance itself
This is now the trick. How can pcell code access to the instance itself ?

Maybe its just possible using some pre-pcell or post-pcell evaluation
trigger functions.


thank you.

 

[Andrew Beckett]

On Tue, 17 Jul 2007 13:49:13 +0200, Guenther Sohler <guenther.sohler@wipro.com>
wrote:

Hallo, I am trying code a pcell with a special functionality.

It works like this:

* user changes pcell properties
* pcell code is evaluated, values are calculated, shapes are drawn,

but NOW: The pcell code should be able to store some calculated values
in the pcell instance itself
This is now the trick. How can pcell code access to the instance itself ?

Maybe its just possible using some pre-pcell or post-pcell evaluation
trigger functions.


thank you.

No, you cannot (safely) do this, and should not try to do it. The reason being
that what would happen if there are multiple instances? The pcell code is only
evaluated once per variant - everyone would scream about performance otherwise -
and so each combination of parameters that exists builds a submaster. Any time
the same combination of parameters is encountered, it simply uses that pre-built
submaster; no need to call anything.

Similarly, if you start in a new session, the instance which triggers the pcell
submaster to be built will effectively be random - and anyway, I doubt you would
want it updating any instance when you open the layout six months after a
tapeout!

What are you actually trying to implement? (i.e. why does it need to do this).
Perhaps I can suggest a better approach?

Regards,

Andrew.
--
Andrew Beckett
Senior Solution Architect
Cadence Design Systems, UK.

 

[cadence]

The pcell code can put put properties on the pcell master but not on
the
pcell instance. Then external programs are allowed to look at the
master of the instance to read these properties. Which programs need
to read these (feedback) properties? If they are programs you are
writing yourself, can't you simply get the properties off the master
instead of expecting them on the instance?

-jim


On Jul 17, 1:49 pm, Guenther Sohler <guenther.soh...@wipro.com> wrote:

Hallo, I am trying code a pcell with a special functionality.

It works like this:

* user changes pcell properties
* pcell code is evaluated, values are calculated, shapes are drawn,

but NOW: The pcell code should be able to store some calculated values
in the pcell instance itself
This is now the trick. How can pcell code access to the instance itself ?

Maybe its just possible using some pre-pcell or post-pcell evaluation
trigger functions.

thank you.