How do you find the driving cell?

Hello Sanjay,
You specify only 1 logic depth of a driver pin, which is an output pin, that's why so see the input pins. Try max_logic_depth of 2.

Synthman -

Thanks,

Hi,

I don't think you want a logic depth of 2 here. If the result of [get_attr drivers] is already a leaf driver, then you already have your result. However if [get_attr drivers] returns a hierarchical boundary pin (and I'm assuming this is the tricky case you need to handle), then you want to get the fanin with the max PIN depth set to 1. Below is some code to help distinguish between the hierarchical boundary pin case and the trivial case.

Hope this helps...

- Denis

proc is_hier_boundary {pin} {
return [expr {[basename [dirname [dirname [dirname $pin]]]] eq "instances_hier"}]
}

proc leaf_driver {net} {
set drvrs [get_attribute drivers $net]
if {! [llength $drvrs]} {
return [list]
}

# get the first driver of the net (in case there are many)
# could loop over all drivers instead
set drvr [lindex $drvrs 0]

if {[is_hier_boundary $drvr]} {
# this is a hierarchical boundary, trace to find the leaf driver
return [fanin -structural -max_pin_depth 1 $drvr]
}

# the net is already driven by a leaf driver
return $drvr
}

Many thanks, this is what I was looking for.

Sanjay