NFC Standards and Communication Methods | NEXTY Electronics, an electronic components and semiconductor trading company

NFC (Near Field Communication), widely used in smartphone payments and transportation IC cards, has become an essential technology in modern life. Why is NFC attracting so much attention? The reason is its three characteristics: safety, convenience, and low power consumption.
This article systematically organizes the NFC standard system and communication methods, touches on the latest technological trends and future directions, and is written in a way that even beginners can understand.

NFC basics

NFC is a type of wireless communication technology, but unlike Bluetooth and Wi-Fi, it is characterized by its extremely short communication distance.
The frequency band used is 13.56MHz, which is in the ISM (Industrial, Scientific and Medical) band. This band is available worldwide without a license, facilitating global adoption.
For general close-range applications, the communication distance is about 10 cm according to ISO/IEC 14443. This is due to a design concept that emphasizes security. Because communication is limited to short distances, the risk of eavesdropping by third parties and relay attacks is reduced.
The communication speed for ISO/IEC 14443 is 106kbps to 848kbps, which is not suitable for transferring videos or large amounts of data, but is sufficient for exchanging authentication and configuration information. For ISO/IEC 15693 (Type 5), the speed is 26 to 53kbps.

Principle of communication between NFC reader/writer and NFC tag/card

NFC communication is performed using magnetic field coupling, which utilizes electromagnetic induction. The magnetic field generated by ANTENNA COILS on the sending side is received by the coil on the receiving side, transmitting power and signals. This mechanism makes it possible for passive tags (tags without POWER SUPPLIES) to operate. For example, transportation IC cards and NFC tags operate using electromagnetic energy supplied by a reader.
In terms of security, encryption technologies such as AES and DES are used, and authentication protocols are also incorporated. This ensures a high level of safety when exchanging payments and personal information. In addition, CRC (Cyclic Redundancy Check) is used for error checking, ensuring the reliability of communication.

Communication Modes and Standards

NFC has three main communication modes.

① Card emulation mode

This mode allows smartphones and devices to behave like IC cards. It is a typical method used in transportation IC cards and mobile payments (EMVCo), and complies with ISO/IEC 14443. This ensures compatibility with existing CARD READER and makes implementation easy.

② Reader/Writer Mode

This mode allows NFC devices to read and write tags and cards. Tags are classified into Type 1 to Type 5, and differ in capacity, communication speed, and security features. For example, Type 2 tags are low-cost and widely available, and are suitable for storing product information and URLs. This mode allows smartphones to be used as payment terminals.

③ P2P mode (Peer-to-Peer)

This mode allows two-way communication between NFC-compatible devices. It complies with ISO/IEC 18092 (NFCIP-1). Currently, it is mainly used for communication between devices other than smartphones, such as parameter settings for industrial and automotive equipment.

P2P communication between smartphones (such as Android Beam) has been discontinued since Android 10 and is not generally available on current smartphones.

These modes are used depending on the application. Card emulation is suitable for payments and authentication, reader/writer mode is suitable for providing product information, and P2P mode is suitable for communication between devices. In the next chapter, we will explain the standards that support these and the role of the NFC Forum.

Applications using NFC communication

When using Bluetooth wireless earphones, you must first pair them with your smartphone. NFC communication is used to simplify this "pairing procedure."
Wireless earphones have a built-in NFC tag that stores information necessary for pairing, such as the MAC address. When a user holds their smartphone over the earphones, the earphones send this information in NDEF format (NDEF will be explained in detail in the next chapter). The smartphone can automatically complete the pairing setup simply by reading the NDEF, eliminating the need for the user to perform any complicated operations.
Once pairing is complete, the main communication of music, voice data, etc. is done using Bluetooth. In other words, NFC is a means of safely and reliably transferring pairing information over short distances, while Bluetooth is a means of transmitting the main data at high speed.

Communication between wireless earphones and a smartphone

Typical applications that use the NDEF format

NDEF is a standard data format used for information exchange using NFC, enabling a wide range of applications. Representative examples are shown below.

1. Smart Poster/URL Link

Store a URL on the NFC tag and tap it with your smartphone to open the web page.
It is widely used for promotions at stores and events, product introductions, campaign guidance, etc.

2. Mobile payments and transportation IC cards

Using Card Emulation mode, your smartphone acts like an IC card, allowing you to make payments and board trains by communicating with payment terminals and ticket gates.
Examples: Apple Pay, Google Pay, Suica, PASMO, etc.

3. Pairing and authentication

Bluetooth and Wi-Fi pairing information is exchanged via NDEF, simplifying initial setup.
Used for initial setup of in-vehicle equipment (car navigation, DISPLAY audio), home appliances, and IoT devices.

4. Electronic business cards and contact information exchange

Save contact information in vCard format as an NDEF message and easily exchange contacts between smartphones or via NFC tags.

5. IoT and industrial applications

Product maintenance history, serial information, and traceability information are recorded on the tag.
It can also be used for in-vehicle ECU settings, equipment diagnosis, and trigger information for OTA updates.

The role of the NFC Forum and key specifications: NDEF structure and NFC tag types

The NFC ecosystem cannot exist simply through short-range communication. It is essential that terminals, tags, operating systems, drivers, and service layers such as payment, transportation, and Access control from different manufacturers are interoperable. The NFC Forum plays a central role in this regard. By promoting the spread of NFC, standardizing it, and establishing a certification system, the NFC Forum defines the rules to ensure that "anything works the same regardless of who makes it or where it is used."

NFC Platform Architecture

The NFC Forum architecture is based on the OSI reference model. The physical layer complies with ISO/IEC 14443 and 18092, and the data link layer ensures reliability with the NFC Digital Protocol. The network layer manages logical links with LLCP and SNEP, and the application layer exchanges data in NDEF format. This enables a variety of secure applications, including payment, authentication, and IoT integration.

NFC Specification Architecture (Source: NFC Forum)

NDEF (NFC Data Exchange Format)

This time, we will explain in detail the important NDEF data structures.
NDEF is a common language for exchanging data over NFC. NDEF stores payloads such as URLs, text, vCards, and Wi-Fi/BLE setting information in units called records, and provides a mechanism for bundling and transporting them in messages. What's important is that NDEF can be used for both tags and P2P. This means that whether a smartphone is reading a tag on a poster or passing data between smartphones, information flows in the same format, simplifying app implementation.

Basic structure of an NDEF message

NDEF record format

NDEF message	NDEF record	NDEF record	NDEF record	A Message consists of multiple Records

NDEF record	Record header	Record payload		Record consists of Header and Payload

NDEF record header	Flags & TNF 1 byte	Type Length 1 byte	Payload Length 1 or 4 bytes	ID Length 1 byte	Payload Type variable	Payload ID variable

NDEF record fields

Field

Length

Description

Flags and TNF

1 byte

Flags are bit information contained in the first byte of an NDEF record that indicate the structure and role of the record. TNF is a value that indicates the type of format represented by 3 bits. It determines what type of data the payload is.

Flags and TNF format

Tags and TNF
MB 1 bit	ME 1 bit	CF 1 bit	SR 1 bit	IL 1 bit	TNF 3 bits

Flags field

Field	Length	Description
MB	1 bit	Message Begin. A flag indicating that this is the first record in a message.
ME	1 bit	Message End. Indicates the last record of the message.
CF	1 bit	Chunked Flag. Flag to use if the payload is split into multiple chunks.
SR	1 bit	Short Flag. A flag that is set if the payload length is 255 bytes or less, allowing the length field to be 1 byte.
IL	1 bit	ID Length. A flag that is set if the record contains an ID field.
TNF	3 bits	Type Name Format. A 3-bit value that indicates the type of data. 0x01: NFC Forum Well-known Type (e.g. Text, URI) 0x02: MIME Media Type (e.g. image/png) 0x03: Absolute URI 0x04: External Type

Type Length

1 byte

Indicates the length of the record's type information. The type indicates what kind of payload it is. For example, "T" for text, "U" for URI, etc. This field contains the number of bytes in the type name.

Payload Length

1 or 4 bytes

Indicates the length of the payload. The payload is the actual data to be sent (such as a string or URL). It is usually represented as 4 bytes, but if the SR flag is set, it is represented as 1 byte (if it is 255 bytes or less).

ID Length

1 byte

If the record has an ID field, this indicates the length of the ID. The ID is an arbitrary value used to identify the record, and this field exists when the IL flag is set.

Payload Type

variable

This information indicates the type of payload. It is stored in the Type field and its length is determined by the Type Length.
example:

T → text data
U → URI (web link)
MIME types (e.g. image/png) also go here.

Payload ID

variable

This field indicates the ID of the record. This is optional and is used to distinguish between multiple records. This ID is present if the IL flag is set.

An NDEF message consists of multiple records. The first record of a message is marked MB (Message Begin) and the last record is marked ME (Message End). This makes it clear where one message begins and ends.
Each record consists of a header and a payload. The header contains information indicating what type of data the record contains. The TNF (Type Name Format) field in the header indicates the type of data. The TNF value determines whether it is text, a URI (web link), or a MIME type (image or file). The header also contains a flag called SR (Short Record), which is used to simplify size information if the payload is small. The payload is the actual data itself. For example, when sending a URL, the string "https://example.com" is included in the payload. For text, the string contains a language code (e.g., "en" or "ja") and a string.
NDEF is a "container for data exchanged via NFC," and information is stored in units called "records." Understanding this mechanism makes it easy to imagine, for example, writing a URL to an NFC tag and reading it with a smartphone.

Tag Type Specifications

Tag Type Specifications are technical specifications established by the NFC Forum that standardize communication methods and functions for each type of NFC tag. There are definitions for Types 1 to 5, and they stipulate memory capacity, read/write speed, protection functions, command sets, etc. Types 2 and 4 are the most commonly encountered in practice.

Type 1

Standard: ISO/IEC 14443A
Features: Simplest and lowest cost. Memory is about 96 bytes to 2KB.
Communication speed: 106kbps
Uses: Smart posters that store URLs and simple ID information.
Key point: It can be rewritten, but can also be set to read-only if necessary.

Type 2

Standard: ISO/IEC 14443A
Characteristics: The most common type. Memory is about 48 bytes to 2KB.
Communication speed: 106kbps
Applications: event ticketing, Access control, product authentication, etc.
Key points: Low price and NDEF compatible.

Type 3

Standard: JIS X 6319-4 (FeliCa method)
Characteristics: Widely used in Japan. Memory ranges from a few KB to a maximum of 1MB.
Communication speed: 212kbps or 424kbps
Uses: Transportation IC cards, electronic money, ID cards.
Key points: High performance but high price.

Type 4

Standard: ISO/IEC 14443 (Type A/B)
Features: Enhanced security features, memory range from 32KB to 1MB.
Communication speed: 106kbps - 424kbps
Uses: Payment cards, security authentication.
Key point: Supports ISO-DEP protocol, enabling encryption and authentication.

Type 5

Standard: ISO/IEC 15693
Features: Long-distance communication (up to approximately 1m), flexible memory capacity.
Communication speed: Generally around 26kbps, high rate around 53kbps
Applications: Logistics management, inventory control, industrial applications.
Key point: Based on RFID technology, it can be read over a wide range.

LLCP and SNEP

LLCP and SNEP are protocols used for NFC P2P communication.

LLCP (Logical Link Control Protocol)
It is a link management protocol that allows two-way communication between NFC devices. It corresponds to the data link layer of the OSI model, and enables connection establishment and disconnection, as well as simultaneous communication between multiple apps. Simply put, it is the foundation for conversations over NFC.
SNEP (Simple NDEF Exchange Protocol)
It is an application layer protocol that runs on LLCP and is a mechanism for exchanging NDEF messages (URLs, text, etc.). In other words, it is the rules for sending and receiving NDEF data.

NCI (NFC Controller Interface)

NCI is an abstraction layer that allows a device's OS or application to handle NFC chips. NCI standardizes the exchange of commands and events between the host (OS/driver) and the NFC controller, absorbing vendor differences. This allows applications to handle events such as "tag detected," "NDEF read," and "received via P2P" using a consistent API. For implementers, this makes it easier to replace chips from multiple manufacturers with the same design, reducing procurement risks and maintenance burdens.

Summary

NFC is not just a short-range communication technology; it is used in a wide range of fields, including payment, authentication, IoT, and automotive applications. Understanding communication modes and designing in compliance with standards will determine product reliability and market suitability. Going forward, further evolution is expected, including hybrid use of NFC with Bluetooth LE or UWB, and integration into automotive systems.