Hello Everyone,
One of my colleagues asked me another interesting question. This is about the
NC pins.
I searched BIRD189 for "NC" and "no-connect". NC appears only in the [Pin] and
[Pin
Mapping] keywords of the examples, and in one sentence where both NC and
no-connect
appears once, explaining the pint types in the [Pin] keyword.
The IBIS spec does not give much more detail on defining what an NC pin really
is.
The question is this: Does NC mean that we are not making any connections to
that pin
on the inside of the component (i.e. the package side of the pin), or are we
saying that
nothing should be connected to the pin from the board side?
The reason this question was raised is because we were wondering whether BIRD189
allows or prohibits any interconnect/package models to involve NC pins. The
BIRD
doesn't say anything on that. Does it mean that one could make a package model
which goes to an NC pin? After all, I have seen chips in which NC meant that
the user
should not connect anything to the NC pin on the board, while the chip did have
stuff
connected to it from the inside (probably for super-secret testing purposes,
etc...).
Thanks,
Arpad
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