Here is where to obtain the current release specification from the Philips web site.

I²C Bus Specification

The following is an excerpt from the specification...



From reading this it should be clear that Philips grants a priviledge to use the I²C bus if the circuit uses a Philips component with a Philips implementation of the bus on the part. There is no specific clarification as to whether the part has be a master or a slave.

So as long as you meet that requirement and write your bitbang algorithm within the specification parameters you are good to go.

If you use a I²C type peripheral from another manufacturer or if you design your own interface between 2 or more parts then you need to obtain a separate liscense from Philips. That is at least required if you claim I²C compatibility for your product and you use the Philips I²C logo and/or trademarked terms in your product documentation and claims.

On the other hand if you do not claim I²C compatibility and you refrain from using Philips trademarks in your product claims and documentation then it is unlikely that a Philips liscense would be required. You can see this in some interesting ways by observing that many component vendors have similar interfaces on their components but refer to that interface by another name.

The last gray area to consider is the following. If a chip vendor such as manufacturer of a serial interface EEPROM claims full I²C compatibility and uses the trademarks of Philips in their product documentation then they will have a license if they have made proper arrangements with Philips. However it is not clear that if you use these licensed parts in your product if any I²C license is granted upon you the user. In these cases I suggest that you contact both Philips AND the part manufacturer.

Michael Karas