Three Modes of NFC
In addition to three communication technologies, NFC devices defined by the NFC Forum Specifications ('NFC Forum Devices') support three modes of operation:
- Card Emulation Mode can substitute the functionality of existing contactless IC cards
- Reader/Writer Mode can be used to read information from NFC tags
- Peer-to-Peer Mode allows to exchange messages (containing for example information like web or e-mail addresses) directly between NFC Forum devices
A functionality called Mode Switch manages how the three communications systems and three modes of operation are processed in an NFC Forum device. This function is an essential part of the NFC Forum technical specifications.
NFC Forum Tags
NFC Forum Devices are also required to support the Reader/Writer mode including support to read and write NFC Forum Tags. The NFC Forum has selected four types of tags that each NFC device has to support.
Type 1 is based on Topaz by Broadcom Corporation, Type 2 on MIFARE Ultralight by NXP Semiconductors, Type 4 on tags compliant with ISO/IEC 14443 (a typical example is DESFire of NXP Semiconductors), and Type 3 on Sony FeliCa compliant with the Japanese Industrial Standard JIS X 6319-4. Type 5 Tag Operation Specification has also been released to add support for tags with ISO/IEC 15693 standard.
To encapsulate application data to be transferred over NFC, the NFC Forum has defined a data format called NFC Data Exchange Format (NDEF). For all four NFC Forum Tag Types the NFC Forum has provided specifications describing how to store NDEF messages on them. Applications using NDEF as a data format can therefore make use of all of those tag types interchangeably.