In addition to three communication technologies, NFC devices defined by the NFC Forum Specifications ('NFC Forum Devices') support three modes of operation:
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 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.
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.