single wire protocol (NFC) (SWP)
Single Wire Protocol (SWP) is a standardized interface via which SIM cards communicate with the Near Field Communication( NFC) controller in the smartphone.
The SWP interface is also called a single wire interface because it has only one data and ground wire. Conceptually, it is comparable to the I2C bus. The SWP protocol can be used to control NFC applications in the smartphone 's SIM card. The SWP protocol has been standardized by the European Telecommunications Standards Institute( ETSI).