When people need to communicate with each other, we use language. If two people speak the same language, they can talk all they want about all sorts of topics. If they don’t speak the same language, communication is difficult. Likewise, electronic parts need to communicate – and they also have their own languages. There are a few common languages that are spoken. The most popular ones are TTL Serial, SPI, I2C, I2S, 1-Wire, and Parallel (such as 8080 or 6800). Of these, Parallel and SPI can ‘share a bus’ using a select line – multiple devices can share the pins as long as they have a single pin that can be used to indicate who is permitted to speak at one time. 1-Wire and I2C are true shared-bus protocols – you can have 100+ components all talking at once using the same 2 wires (for I2C) or 1-wire (for the aptly-named 1-wire). 1-Wire is much slower than I2C and is a strongly-patented protocol owned by Maxim so you won’t see a lot of devices out there other than Maxim/Dallas parts that use 1-wire.