finding nodes and instances in skill

my ultimate goal is to generate a skill routine that will extract timing
information from a spectre(most likely run through ocean) to allow for
digital timing verification on custom digital blocks. I want to get setup
and hold margin.

In order to accomplish this I need to find the clock and data inputs of all
flip-flops in the schematic. I need a function that will search through the
hierarchy for instances that are flip-flops and then return the nodes
connected to the data and clock inputs. These nodes that are returned need
to be correct with respect to the simulation schematic hierarchy. IE if a
flip-flop is two levels down, function should return
ILEVEL1/ILEVE2/NODENAME.

If anyone has any suggestions on methods to search a simulation schematic
and return all nodes connected to each flip-flop instance I would
appreciate it.

Also if anyone knows of the location of scripts that have already solved the
digital timing verification problem, I would appreciate that.

Thanks
Mark

 

Your best bet is to use OSS to flatten the schematic to a new view
(simFlattenWithArgs is the function to look at). Then check each
instance in this view, and if it's a flop, look at its instTerms
and find the nets connected to the inputs you're interested in.
The flattener will take take of the hierarchical net naming for
you.

- Keith

 

Mark Summers wrote:
[snip]

I've taken a stab at this before. The code pretty much recursively
decends the design hierarchy, building the hierarchy path one instance
at a time. Where I became stuck was on signals whose local nets are
connected to something further up the design hierarchy or at the
top-level.

On these cases the node name I would build was "/DUT/I34/I35/VDD".
Trying to get the voltage using Ocean would fail:

v( "/DUT/I34/I35/VDD". ?results 'tran)

because this is actually connected to the top level "VDD" node. In
these cases the following would work:

v( "/VDD" ?results 'tran)

Does anyone know if there is a public function that can used to map the
local node name to the one at the highest level of hierarchy?

Jason

 

I have the same problem that you are describing. Any help would be good

 

Personally I wouldn't do this by flattening the schematic - unless you really
need to. If you can gather the information whilst traversing the hierarchy
(using some kind of recursive function) that will generally be more efficient
than producing a flattened database.

Sometimes you need a persistent flattened database (often for floorplanning
type reasons) - but for this type of usage, I'd probably not go about it by
flattening the hierarchy.

If however you're likely to need the flattened hierarchy information several
times for different purposes, then it may be worth doing. Also, if the design
size is small, it doesn't really matter.

A few years back one of my colleagues used a flattening type approach
(although he didn't do it with OSS) - and once I'd made some suggestions about
doing it recursively, and we'd optimised the code, a run with a very large
database went from several hours down to something like 90 seconds...

Of course, your mileage may vary.

Andrew.

 

OSS, not OOS. Open Simulation System. Look for it in cdsdoc.
Nothing like reading the manual to learn how to do something ;-)

Mind you, consider my previous post - this may be the simplest method, but not
necessarily the most efficient (depending on your needs).

Andrew.

 

good

Hi Mark,

I've been in touch with Cadence support (very helpful) and have
something that should work.

geGetAdjustedPath() is the procedure we are looking for. However it
requires a windowId as the first argument. Providing a cellView as the
third argument returns the path relative to that instance, so passing
the top-level cellview as this argument is the same as omitting it. In
these cases I'm not sure why the window argument would still be
required, but the function fails if a valid windowId is not passed.

If you already have a window with the design open you can use
hiGetCurrentWindow() to get the window ID. If not, you can just create
a new window like so:

myWindow=hiCreateWindow('default "graphics" "t")

This new window will not get displayed. Be sure to close it with
hiCloseWindow() afterward. Unfortunately, there is something wrong
with my installation and doing this causes ICFB to crash, but the
support person tested it successfully.

Let us know if you have success with this.

Jason

 

good

Hi Mark,

I've been in touch with Cadence support (very helpful) and have
something that should work.

geGetAdjustedPath() is the procedure we are looking for. However it
requires a windowId as the first argument. Providing a cellView as the
third argument returns the path relative to that instance, so passing
the top-level cellview as this argument is the same as omitting it. In
these cases I'm not sure why the window argument would still be
required, but the function fails if a valid windowId is not passed.

If you already have a window with the design open you can use
hiGetCurrentWindow() to get the window ID. If not, you can just create
a new window like so:

myWindow=hiCreateWindow('default "graphics" "t")

This new window will not get displayed. Be sure to close it with
hiCloseWindow() afterward. Unfortunately, there is something wrong
with my installation and doing this causes ICFB to crash, but the
support person tested it successfully.

Let us know if you have success with this.

Jason