> Date:    Tue, 17 Sep 1996 17:41:07 -0500
> From:    John Payson <supercat@MCS.COM>
> Subject: Re: IIC Royalties?

> [Brian Boles at Microchip wrote]
> >      Only I2C implementations in SILICON (custom or ASIC) are subject to
> >      royalty.  Users of that silicon or software implementations do not
> >      have to pay any royalty.
>
> My impression, going along with this, is as follows:
...
> [4] Brian made mention of custom silicon or PLD's; what about use of
>     standard logic for I2C handling?  I think a clock-extender and start-
>     detector could both be built using only a pair of quad open-collector
>     2-input NAND gates.

Not quite: Brian said custom or _ASIC_ - PLD would still be firmware,
not silicon. My impression that Philips' primary interest is to make
sure there are no (incompatible) variations of I2C out there. The
patent on the arbitration scheme went out a long time ago (btw, CAN
uses exactly the same method).

I haven't checked, by I'm fairly sure that any patents on I2C either
have expired, or are on the way of expiring soon, since I2C is
actually quite old (anybody knows the exact dates?). There are other
ways that Philips can protect I2C. One is by trademarking - anyone who
wants to claim the product is I2C compatible, MUST conform to the
specs defined by Philips. Of course, we want Philips to maintain this
situation, so we know that our devices will work together. Another one
is by pattern protection, which allows protection for a longer time
than patents, and which I would believe is a more relevant type of
protection here.

However, I'm fairly sure that Philips is mainly interested in making
sure I2C remains a well-defined standard, and are happy that it
spreads, which will indirectly increase their revenue. With their
trade mark protection, nobody can make a PCF8574 copy and claim it to
be an I2C device.  I haven't experienced any attempts by Philips to
pursue and hunt-down I2C system builders, but completely on the
contrary - Philips has always been very friendly and supportive
regarding I2C, whenever I have been in touch with them.

John also wrote:

> I think the only place this is going to cause any trouble is if someone
> tries to sell a device which is intended to act as a slave or a non-
> exclusive master and the device uses Philips' unique protocol features.

I think there are two cases that will cause trouble:

1) If you manufacture a device that claims to do I2C, but isn't (licensed).
[Philips can hit you with trade mark rights.]
2) If you manufacture a device which does I2C, but says it is something
else, and that competes with Philips own I2C devices.
[Philips can hit you with pattern protection or, possibly, patents.]