NFC Communication Modes

By Robert R. Sabella

The Near Field Communication (NFC) communication modes determine how two NFC-enabled devices talk to each other. A communication consists of an initiator, which is the device that starts the communication, and a target, which is the device that receives the initial signal from the initiator. The following discussion helps you understand the two modes of communication.

NFC active mode

When working in active mode, the initiator and target both have power supplies, so it isn’t necessary for the initiator to send power to the target to allow the target to perform useful tasks. The two devices use alternate signal transmissions to send data to each other. In other words, both devices generate an RF field and send data by modulating that RF field.

When in active mode, the two devices use an Amplitude Shift Keying (ASK) modulation scheme. To avoid collisions, the receiving device turns off its field, so only one device is transmitting at any given time. Advantages of using active mode are that the data rate is usually higher and it’s theoretically possible to work at longer distances.

NFC passive mode

When working in passive mode, the initiator sends RF energy to the target to power it. The target modulates this energy in order to send data back to the initiator. Unlike active mode, the target relies on load modulation (making changes to the amplitude of the original signal) to transmit data. It doesn’t generate a field of its own, but rather changes the field of the initiator to transfer data.