There is language and terminology in the description of I2C communication that have definitions specific to I2C. That word usage is defined below and may be used in the rest of this document without explanation. This table was adapted from the Philips I2C specification.
| TERM | Description |
|---|---|
| Transmitter | The device that shifts data out onto the bus. |
| Receiver | The device that shifts data in from the bus. |
| Master | The device that initiates a transfer, generates clock signals and terminates a transfer. |
| Slave | The device addressed by the master. |
| Multi-master | A bus with more than one device that can initiate data transfers. |
| Arbitration | Procedure to ensure that only one master at a time controls the bus. Winning arbitration ensures that the message is not corrupted. |
| Synchronization | Procedure to synchronize the clocks of two or more devices on the bus. |
| Idle | No master is controlling the bus, and both SDA and SCL lines are high. |
| Active | Any time one or more master devices are controlling the bus. |
| Addressed Slave | Slave device that has received a matching address and is actively being clocked by a master. |
| Matching Address | Address byte that is clocked into a slave that matches the value stored in SSPxADD. |
| Write Request | Slave receives a matching address with R/W bit clear, and is ready to clock in data. |
| Read Request | Master sends an address byte with the R/W bit set, indicating that it wishes to clock data out of the Slave. This data is the next and all following bytes until a Restart or Stop. |
| Clock Stretching | When a device on the bus hold SCL low to stall communication. |
| Bus Collision | Any time the SDA line is sampled low by the module while it is outputting and expected high state. |