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TN1216
Technical note
NFC guide
Introduction
Near-field communication, NFC, is a technology used to provide short-range wireless
connectivity to carry two-way interactions between electronic devices.
NFC is promoted and maintained by the NFC Forum, a non-profit industry association
created with the goal to advance the use of NFC technology in consumer electronics, mobile
devices and PCs. The NFC Forum promotes implementation and standardization of the
NFC technology to ensure interoperability between devices and services.
NFC is a flavor of RFID (radio-frequency identification), but it additionally has a specific set
of standards ensuring interoperability of NFC-enabled equipment. NFC standards determine
the operating environment and data formats, transfer rates, modulation, and so on.
NFC uses inductive coupling between two NFC devices and operates with electromagnetic
field at 13.56 MHz - a license-free allocation in the HF portion of the radio spectrum. An
NFC device can draw power from the field generated by another NFC device. This enables
some NFC devices to be exempt of power supply and to take form of tiny objects such as
tags, stickers, key fobs or cards.
Because the transmission range is so short, NFC-enabled transactions are inherently more
secure than transactions in some other wireless technologies. With little energy required to
cover the interaction zone with RF electromagnetic field, the NFC technology consumes
very low power and is ideal for battery-powered devices such as smartphones.
This technical note provides basic information on near-field communication technology. It
explains different NFC operation and communication modes, gives insight to modulation,
data signaling and bit coding, protocols and standards. It also introduces some of
STMicroelectronics components designed for use in NFC-enabled devices.
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Contents
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Contents
1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3
Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1
3.2
3.3
3.4
Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.1
Passive mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.2
Active mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Modes of communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.1
Read / write mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.2
Card emulation mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.3
Peer-to-peer mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Tag types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
3.3.1
Type-1 tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.2
Type-2 tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3.3
Type-3 tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.4
Type-4 tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3.5
Type-5 tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
RF field and over-the-air interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4.1
Inductive coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4.2
Direct and indirect modulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Modulation index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Load modulation principle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
3.5
3.4.3
Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.4.4
Energy harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.5.1
NFC-A data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
NFC-A PCD-to-PICC data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
NFC-A PICC-to-PCD data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
3.5.2
NFC-B data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
NFC-B PCD-to-PICC data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
NFC-B PICC-to-PCD data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
3.5.3
NFC-V data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
NFC-V VCD-to-VICC data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
NFC-V VICC-to-VCD data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
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3.5.4
4
Data transfer summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.6
NFC system architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.7
NDEF structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.7.1
Payload length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.7.2
Payload type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.7.3
Payload identifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4.1
Legacy ISO/IEC standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1.1
ISO/IEC 14443 - Proximity cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
ISO/IEC 14443-1:2008 - Physical characteristics. . . . . . . . . . . . . . . . . . . . . . . . .28
ISO/IEC 14443-2:2015 - Radio frequency power and signal balance . . . . . . . . .28
ISO/IEC 14443-3:2014 - Initialization and anti-collision . . . . . . . . . . . . . . . . . . . .28
ISO/IEC 14443-4:2015 - Transmission protocol . . . . . . . . . . . . . . . . . . . . . . . . . .28
4.1.2
ISO/IEC 15693 - Vicinity cards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
ISO/IEC 15693-1:2010(E) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
ISO/IEC 15693-2:2009 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
ISO/IEC 15693-3:2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
4.2
5
Standards specific to NFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2.1
ISO/IEC 18092 - NFC interface and protocol 1 (NFCIP-1) . . . . . . . . . . 29
4.2.2
ECMA-340: 2013 - NFC interface and protocol 1 (NFCIP-1) . . . . . . . . . 29
4.2.3
ECMA-352: 2013 - NFC interface and protocol 2 (NFCIP-2) . . . . . . . . . 29
NFC interface ICs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.1
Static tag IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.2
Dynamic tag IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.3
P2P interface IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
7
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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List of tables
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List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
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NFC terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Types of NFC tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Modulation index versus modulation depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
NFC data transfer bit signaling, coding and rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
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List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Examples of NFC-enabled applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Passive mode of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
NFC modes of operation and communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Modulation index versus modulation depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Example of RF circuitry in NFC devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
PICC antenna classes defined in ISO/IEC 14443 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
NFC Forum reference PCD designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
NFC Forum reference PICC designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Energy harvesting from RF field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
NFC-A PCD-to-PICC data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
NFC-A PICC-to-PCD data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
NFC-B PCD-to-PICC data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
NFC-B PICC-to-PCD data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
NFC-V VCD-to-VICC data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
NFC-V VICC-to-VCD data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
NFC data transfer summary diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
NFC system functional stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
NDEF message structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Simplified stack of NFC layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Map of NFC-related standards and specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Static tag IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Dynamic tag IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
P2P interface IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
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Overview
1
TN1216
Overview
Near-field communication, NFC, defines two types of NFC devices. These are known as
initiator and target. As the names imply, the initiator is the device that initiates the
communication. It also controls the data exchanges. The target device is the one that
responded to the request from the initiator and accepted the communication with the initiator
to happen.
NFC initiator can be, for example, an RFID reader or a smartphone. In proximity of another
NFC device, it initiates a communication then collects information from it or runs an action
according to that information. Identification of a commercial article bearing an NFC tag is a
good example of collecting information. Pairing of a Bluetooth music player (NFC initiator)
with an active Bluetooth loudspeaker (NFC target) is a good example of an action resulting
from the NFC transaction.
For NFC technology to ensure interoperability and become widely accepted in many
applications, the system has been defined such as to comply with a number of international
standards by recognized standardization bodies. The initial intention of NFC Forum was to
complement legacy ISO/IEC RFID-related standards with peer-to-peer contactless
communication mode. Today, the NFC-specific international standards like ISO/IEC 18092
and NFC Forum specifications go beyond this initial goal. For more detail on the set of
standards and specifications forming the NFC technology, refer to Section 4.
Figure 1 indicates a few examples of a large variety of applications.
NFC recognizes two modes of operation, passive mode and active mode, described in
Section 3.1 and, three modes of communication, read/write mode, card emulation mode
and peer-to-peer mode, described in Section 3.2. NFC also defines tag types, as described
in Section 3.3.
Figure 1. Examples of NFC-enabled applications
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Glossary
Glossary
Table 1 lists terms related to NFC technology, used in this document.
Table 1. NFC terminology
Term
NFC
NFC Forum
NFC Forum device
Definition
Near-field communication.
Association of industry actors, promoting NFC technology.
Device compliant with NFC Forum specifications.
Activity
Process within an NFC Forum device with well-defined pre-conditions and
post-conditions. An activity can only start when its pre-conditions are
fulfilled. When an activity ends, its post-conditions are fulfilled.
Initiator
Role of an NFC Forum device reached when an NFC Forum device in poll
mode has gone through a number of activities; in this role, the NFC Forum
device communicates using NDEP protocol.
Target
Role of an NFC Forum device reached when the NFC Forum device has
gone through a number of activities in which the NFC Forum device
communicates using the NDEP Protocol.
Poll mode
Initial mode of an NFC Forum device when it generates a carrier and
probes (polls) for other devices.
Polling device, poller
NFC Forum device in poll mode, also used as substitute of ISO/IECdefined PCD.
Listen mode
Listening device, listener
Initial mode of an NFC Forum device when it does not generate a carrier;
in this mode, the NFC Forum device listens for the RF field of another
device.
NFC Forum device in listen mode, also used as substitute of ISO/IECdefined PICC.
PCD (VCD)
Short of proximity (vicinity) coupling device - a technology subset defined
in ISO/IEC standards for reader / writers, with a defined set of commands.
PICC (VICC)
Short of proximity (vicinity) IC card - a technology subset defined in
ISO/IEC standards for cards, with a defined set of commands.
Card
PICC in form of a credit card, without own power source and not
generating RF electromagnetic field, capable of communicating with a
reader / writer.
Tag
PICC in form of a patch, key fob and the like, without own power source
and not generating RF electromagnetic field, capable of communicating
with a reader / writer.
Peer
One of actors of NFC communication in peer-to-peer mode.
Reader / writer
Role of an NFC Forum device reached when an NFC Forum device in poll
mode has gone through a number of activities. In this mode, the NFC
Forum device behaves like PCD.
Card emulator
A role of an NFC Forum device, reached when an NFC Forum device in
listen mode has gone through a number of Activities and in which the NFC
Forum Device behaves like PICC.
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Glossary
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Table 1. NFC terminology (continued)
Term
Peer-to-peer, P2P
Communication mode defined in NFC Forum used to establish a link
between two NFC devices and allow fast data transfer.
Active device
Term defined in this document. Device that, in interaction with another NFC
device, momentarily generates RF electromagnetic field.
Passive device
Term defined in this document. Device that, in interaction with another NFC
device, momentarily does not generate RF electromagnetic field.
Active mode
One of two modes of operation, as defined in NFC Forum, in which two
active devices are in communication.
Passive mode
One of two modes of operation, as defined in NFC Forum, in which an
active device communicates with a passive device.
RF
Short of radio frequency.
RFID
Short of radio-frequency identification; a standardized technology, basis for
the NFC technology.
NDEP
Short of NFC data exchange protocol; a half-duplex block transmission
protocol defined in ISO/IEC 18092.
NFCIP
Short of NFC interface and protocol.
NDEF
Short of NFC data exchange format.
DEP
SNEP
HF
8/35
Definition
Short of data exchange protocol.
Short of simple NDEF exchange protocol.
Short of high frequency.
MCU
Short of microcontroller unit.
ISO
Short of International standardization organization.
IEC
Short of International electro-technical commission.
ASK
Short of amplitude shift keying.
FSK
Short of frequency shift keying.
PSK
Short of phase shift keying.
OOK
Short of on-off keying.
VHBR
Short of very high bitrate.
ECMA
Short of European computer manufacturers association.
URI
Short of unified resource identifier; it can be URL for unified resource
locator or URN for unified resource name.
MIME
Short of multipurpose Internet mail extensions, an Internet standard
extending the format of email.
FELICA, net FeliCa
Short of felicity card; RFID smartcard system by Sony Corporation.
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Technology
3
Technology
3.1
Modes of operation
3.1.1
Passive mode
In passive mode of operation, only one NFC device generates RF field. In that sense, it is
active and always plays the role of NFC initiator. The other device is passive and it always
plays the role of NFC target.
The active device transfers data by modulating the carrier of the field it generates. The
modulation is detected by the passive device and interpreted as data. The passive device
transfers data to the active device by load-modulating the intensity of the field. The active
device detects the variation and interprets it as data.
Depending on the size of the antenna and the field modulation magnitude, operating
distances up to 10 cm and discrete data rates ranging from 106 kbit/s to up to 848 kbit/s are
possible.
In either direction, the data to transfer is encoded with methods defined in ISO/IEC RFID
and in NFC-specific standard.
This mode is typically used for reading contactless tags or smartcards.
3.1.2
Active mode
In active mode of operation, both NFC devices generate RF electromagnetic field. Each
side transmits data using ASK (amplitude shift keying) modulation scheme. Compared to
passive mode, larger operating distances of up to 20 cm (depending on the protocol) can be
reached. High data transfer rates called VHBR (very high bitrate) of up to 6.78 Mbit/s can be
reached, if using PSK (phase shift keying) modulation type.
The radio transmissions are half-duplex as the same radio channel is used for both transmit
and receive. To prevent collisions, the devices operate what is termed a listen-before-talk
protocol.
Figure 2. Passive mode of operation
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Technology
3.2
TN1216
Modes of communication
Figure 3 shows the smartphone in the center taking one of three communication modes
recognized by NFC Forum: read / write mode, card emulation mode and peer-to-peer mode.
Figure 3. NFC modes of operation and communication
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3.2.1
Read / write mode
An NFC device communicating in read / write mode reads data from or writes data to an
NFC object. It may then act depending on the information read from the object.
For example, an NFC phone getting in proximity of an NFC tag can retrieve a URL and go to
the corresponding website. It can send an SMS (short message service) text without typing,
obtain coupons, start a pairing action, obtain a contact vCard and the like.
This mode uses NFC Forum-defined message format. The data transfer is not secure.
3.2.2
Card emulation mode
In this mode, the NFC device behaves as a standard contactless smartcard. This allows its
use with the existing contactless smartcard infrastructure for operations such as access
control, contactless payments, firmware exchange or data transfer. NFC device emulating
smartcard usually operates in passive NFC mode and the data transfer is secure.
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Peer-to-peer mode
In peer-to-peer (P2P) mode, the NFC-enabled devices operate in active mode. One of the
devices initiates a communication link. Once the link is established, the devices talk to one
another alternatively, applying listen-before-talk rule. The data exchange in this mode of
communication is faster than in the other communication modes, so bigger amount of data
can be exchanged.
3.3
Tag types
There are four types of NFC tag defined by the NFC Forum. An additional fifth type of tag is
related with NFC-V technology and not yet part of NFC Forum specifications.
Table 2 gives an overview of NFC tag types. The data rates above 100 kbit/s displayed in
the table, as well as used throughout this document, are rounded to the nearest integer
kbit/s.
Table 2. Types of NFC tags
3.3.1
Property
Type 1
Type 2
Type 3
Type 4
Type 5
Standard
ISO/IEC 14443A
ISO/IEC 14443A
ISO/IEC 18092
JIS X 6319-4
FELICA
ISO/IEC 14443A
ISO/IEC 14443B
ISO/IEC 15693
Memory
96 bytes to
2 Kbytes
48 bytes to
2 Kbytes
2 Kbytes
32 Kbytes
up to 8 Kbytes
Data rate
106 kbit/s
106 kbit/s
212 kbit/s,
424 kbit/s
106 kbit/s,
212 kbit/s,
424 kbit/s
26.48 kbit/s
Capability
Read
Re-write
Read-only
Read
Re-write
Read-only
Read
Re-write
Read-only
Read
Re-write
Read-only
Factoryconfigured
Read
Re-write
Read-only
Anti-collision
No
Yes
Yes
Yes
Yes
Note
Simple, cost
effective
-
Higher cost,
complex
applications
-
Vicinity area
Type-1 tag
Type-1 tag is compliant with ISO/IEC 14443A specification. It is read-write-capable and it
may be user-configurable to read-only mode. The memory size ranges from 93 bytes to
2 Kbytes and the communication speed or data rate is of 106 kbit/s.Type-1 tag does not
support anti-collision mechanism.
3.3.2
Type-2 tag
Type-2 tag is compliant with ISO/IEC 14443A specification. It is read-write-capable and it
may be user-configurable to read-only mode. The memory size ranges from 48 bytes to
2 Kbytes and the communication speed or data rate is of 106 kbit/s.Type-2 tag supports
anti-collision mechanism.
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Type-3 tag
Type-3 tag is compliant with ISO/IEC 18092 and JIS X 6319-4 standards, except for
encryption and authentication that are not supported. Although having read / write
capability, a tag of type 3 can be set to read-only mode. Specific service equipment may be
used to allow re-writing of type-3 tag data in the field. Type-3 tag contains two Kbytes of
memory. The data rate is 212 kbit/s or 424 kbit/s. Type-3 tag supports anti-collision
mechanism.
3.3.4
Type-4 tag
Type-4 tag complies with both A and B versions of ISO/IEC 14443 standard. The type-4 tag
is factory-set to read-only mode and specific service equipment is require for updating its
data. Type-4 tag contains up to 32 Kbytes of memory, supports 106 kbit/s, 212 kbit/s and
424 kbit/s data rates, as well as the anti-collision mechanism.
3.3.5
Type-5 tag
Type-5 tag (NFC-V) has recently been adopted by NFC Forum specification. It relies on
ISO/IEC 15693 standard, contains up to eight Kbytes of memory, supports 26.48 kbit/s data
rate and anti-collision mechanism.
3.4
RF field and over-the-air interface
3.4.1
Inductive coupling
NFC uses electromagnetic induction between two loop antennas located within each other's
near field, effectively forming an air-core transformer. It operates within the globally
available and unlicensed radio frequency band of 13.56 MHz. Most of the RF energy is
concentrated in the allowed ±7 kHz bandwidth range, but the full spectral envelope, when
using ASK modulation, may be as wide as 1.8 MHz.
The inductive coupling not only allows the coupled proximity (PCD, PICC) or vicinity (VCD,
VICC) devices to exchange information but also to transfer power from coupling device
(PCD, VCD) to card (PICC, VICC).
As coupling device signals data to card by directly modulating the RF field, the mean energy
of the RF field during data transfer decreases. Different methods of modulation and data
encoding lead to different levels of RF field mean energy decrease. Techniques selected for
VCD and VICC, described in Section 3.5, aim at minimizing the loss of RF field energy
during VCD-to-VICC data transfer. It is of more importance for vicinity equipment than it is
for proximity equipment, as vicinity equipment has to operate at larger coupling distances.
Larger coupling distance cannot be compensated for with more power of the generated RF
field; coupling devices must always respect power limits permitted by international radiofrequency regulations.
3.4.2
Direct and indirect modulation
The coupling device signals data to the listening device by directly modulating the RF field
magnitude. The listening device signals data to the coupling device by load-modulating the
RF field magnitude, applying variable load to its antenna, that is, to the secondary winding
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of the transformer. This indirect modulation causes variations detected by the coupling
device and interpreted as data.
Modulation index
ISO/IEC 14443-2 specifies modulation index. NFC-B 10% modulation means that the
modulation index is 10%, but the specification tolerates values from 8% to 14%. The way of
computing modulation index, as well as commonly used modulation depth, is shown in
Figure 4. There is a deterministic relation between the two measures, illustrated in Table 3.
Figure 4. Modulation index versus modulation depth
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Table 3. Modulation index versus modulation depth
Modulation index
Modulation depth
8%
85.2%
9%
83.5%
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81.8%
11%
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78.6%
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75.4%
The modulation index number is about half of what would suggest a corresponding diagram.
For example, the difference between A and B values in Figure 4 would suggest about 30%,
while the real figure of modulation index for the waveform as displayed is only about 15%.
Users designing NFC-B readers for the first time often misinterpret the 10% modulation
index requirement and set the modulation depth to 90%, which corresponds to about 5%
modulation index and drives their design out of specification.
As stated in section 9.1.2 of ISO/IEC 14443-2, the rise and fall times of the modulation
envelope must be two microseconds or less. The amplitude of overshoot and undershoot
may not exceed 10% of (A - B). Figure 4 illustrates the definition of A and B.
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Load modulation principle
NFC listener signals data by back-scattering the RF field, that is, by causing its intensity to
variate. This is achieved by absorbing more or less energy from the field, through the
technique called load modulation, that is, modulation of load that the listener imposes to the
RF field generated by the reader.
In practice, there are two ways for a listener to do this. In To increase the load antenna,
either a resistor or a capacitor is connected to its terminals. Connecting a resistor has an
effect of drawing current from the antenna, at whatever frequency. At normal condition, the
resonant frequency of the L-C circuit formed by the antenna and the total capacitance at its
output matches the NFC carrier frequency of 13.56 MHz, which minimizes the energy
absorption from the field. Connecting an additional capacitor to the antenna terminals
causes the resonant frequency to change, which translates into an increase of energy
drawn from 13.56 MHz field.
Figure 5 gives an example of NFC-related antenna circuitry in an NFC active device such as
smartphone or card reader and in an NFC passive device such as tag or smartcard.
Figure 5. Example of RF circuitry in NFC devices
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3.4.3
Antenna
ISO/IEC 14443 defines six antenna classes, also referred to in ISO/IEC 15693, as shown in
Figure 6. For each NFC device, the antenna design has to be studied such as to ensure the
optimum performance in the target environment.
The large class-1 antenna has the form factor of a smartcard. It provides the best
performance, with respect to the RF electromagnetic field. On the other side of the
standardized antenna class spectrum, the class-6 antenna is the smallest one and provides
the best integration properties, at the expense of performance.
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Figure 6. PICC antenna classes defined in ISO/IEC 14443
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NFC Forum provides their own PCD (called poller) and PICC (called listener) reference
designs, described in NFC Forum-TS-Analog-1.0 Folder 2.2.1 sheet 16.
When connected to a suitable signal generator and power amplifier, an NFC Forum reference PCD allows commands to be sent to a PICC. The response from the PICC may
then be captured and analyzed by means of associated measurement equipment. The NFC
Forum reference PCD with three different antenna coil designs are based on the standard
PCD class 0 and compensated versions of two of the ISO/IEC-standardized PICC-3 and
PICC-6 antenna coil designs. Named Poller-0, Poller-3, and Poller-6, they are shown in
Figure 7, presented in left-to-right order.
Figure 7. NFC Forum reference PCD designs
06Y9
The NFC Forum reference PICC designs are specified with three forms of antenna coil
design geometry. The coil geometries of Listener-1, Listener-3, and Listener-6, as shown in
Figure 8 in left-to-right order, are based on the outside envelope measurements of the
ISO/IEC-referenced PICC-1, PICC-3, and PICC-6 antenna designations, respectively. The
PCB coil designs are not necessarily identical. The NFC Forum reference PICC allows the
analysis of the signal as sent out by a PCD. For analyzing the frequency and waveforms of
these signals, the NFC Forum reference PICC is equipped with an integrated sense coil.
The NFC Forum reference PICC can also send information back to the PCD, using various
levels of load modulation driven with a suitable signal source. The NFC Forum reference
PICC can be configured to use a number of fixed resistive loads. These resistive load
settings can be used to represent both the typical and the worst-case scenarios to be
encountered by a PCD.
Figure 8. NFC Forum reference PICC designs
06Y9
The NFC Forum reference designs should be used in NFC device test and validation
procedures. They can also serve as reference or guideline, helping NFC device designers
optimize their antenna designs.
3.4.4
Energy harvesting
As described in the previous chapters, NFC technology allows tiny and slim form factor
cards, tabs, patches, key fobs and the like to keep and contactlessly transfer data. This is
thanks to no need of own power supply such as battery. For the period of NFC data transfer,
the passive device draws energy from the RF field generated by the active device.
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Figure 9 illustrates how this operates. Upon application of the RF field to the antenna, the IC
transforms the inducted energy into electrical current to supply the tag IC, the
microcontroller and, possibly, other components such as a sensor. The components can
then operate as long as the RF field is present and strong enough to supply them. The tag
IC can use another GPO to wake up the microcontroller when the RF field is strong enough.
Figure 9. Energy harvesting from RF field
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The energy harvesting function brings multiple benefits:
3.5

enabling battery-free NFC products such as tags or smartcards

waterproofing: no need of connectors or battery compartment

battery life saving on battery-powered devices

automatic wakeup when an NFC device comes in proximity

current supply to other components, in the range of 3 mA
Data transfer
Data transfer between NFC reader (polling device) and listener (a tag or a smartcard) is
ensured with data signaling and data coding. The goal of the data signaling is to reliably
distinguish binary states. The goal of data coding is to organize binary states in a way to
form a binary data stream of logical ones and zeros that can be reliably interpreted by the
data receiving side. For data signaling, techniques like direct RF field modulation (reader)
and indirect RF field modulation (listener) are used. For binary data stream, bit-coding into
ones and zeros is done using know data coding methods. Different types of NFC (NFC-A,
NFC-B, NFC-V) may use different techniques or values.
The following paragraphs bring more details on different aspects of NFC data transfer. NFCF variant is not described as NFC-F is proprietary.
3.5.1
NFC-A data transfer
NFC-A PCD-to-PICC data transfer
NFC-A PCD-to-PICC data signaling employs 100% amplitude modulation (modulation index
of 100%) of the RF field 13.56 MHz carrier. The bits in the binary data stream are encoded
with modified-Miller code, as shown in Figure 10.
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Figure 10. NFC-A PCD-to-PICC data transfer
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With 100% ASK modulation, the RF field completely disappears for short periods of time.
During these field holes, the listening device (card) cannot draw energy from the field. In the
active periods of the 100% ASK modulation, the NFC circuitry on the card must store
enough energy to continue supplying the listener such as tag or card during the field holes.
NFC-A PICC-to-PCD data transfer
NFC-A PICC-to-PCD data signaling goes through varying the load that the listener’s
antenna circuit imposes to the RF field, which causes the RF field magnitude variations. The
rate of the variation is of 848 kHz, that is, eight-time multiple of the data rate, which creates
what is called sub-carrier in the RF field magnitude. The NFC-A listener then keys the subcarrier with a technique called on-off keying (OOK), altering periods with no sub-carrier with
periods of sub-carrier (additional load at the sub-carrier frequency). Specific timing of the
OOK then ensures the encoding of logical zeros and ones in the bitstream; Manchester
coding is used. Figure 11 illustrates all aspects of NFC-A PICC-to-PCD data transfer.
Figure 11. NFC-A PICC-to-PCD data transfer
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3.5.2
NFC-B data transfer
NFC-B PCD-to-PICC data transfer
NFC-B PCD-to-PICC data signaling is based on 10% ASK modulation. The RF field is
continuously present, which allows using NRZ (non-return-to-zero) method to encode data,
as depicted in Figure 12.
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Figure 12. NFC-B PCD-to-PICC data transfer
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NFC-B PICC-to-PCD data transfer
NFC-B PICC-to-PCD data signaling employs, like in the case of NFC-A, the same ASK
modulation of the load in the rhythm of 848 kHz, forming a sub-carrier. However, instead of
on-off keying the sub-carrier, the NFC-B listener uses a technique called BPSK, shifting the
sub-carrier phase at given instants by its half-period. The envelope timing of BPSK phase
shifts follows NRZ coding and ensures a reliable definition of logical levels in the binary data
stream. Figure 13 illustrates all aspects of NFC-B PICC-to-PCD data transfer.
Figure 13. NFC-B PICC-to-PCD data transfer
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NFC-V works are on-going. It is not adopted in NFC Forum yet. That is why, the following
statements regarding NFC-V are subject to change.
3.5.3
NFC-V data transfer
NFC-V VCD-to-VICC data transfer
NFC-V VCD-to-VICC data signaling is based on 10% or 100% ASK modulation. The bit
encoding uses one-out-of-four or one-out-of-256 pulse position modulation (PPM)
technique.Figure 14 shows the way VCD transfers data to VICC, using one-out-of-four PPM
coding. Pulse is in reality a hole taking one eighth of symbol period. One symbol encodes a
bit pair. Pulse of each of four bit-pair values takes a time slot reserved to it within the symbol
period. Start-of-frame (SOF) and end-of-frame (EOF) symbols use time slots not used by
the bit pairs.
The use of PPM for data encoding leads to high RF field duty cycle, in particular in the case
of one-out-of-256 system. This allows using high modulation index ensuring strong data
signaling like in NFC-A, while keeping the RF mean energy decrease low, as in NFC-B.
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Figure 14. NFC-V VCD-to-VICC data transfer
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NFC-V VICC-to-VCD data transfer
NFC-V VICC-to-VCD data signaling is done with 10% ASK modulation creating 424 kHz
sub-carrier and OOK on the sub-carrier. Manchester code is used to encode data bitstream.
Another variant of NFC-V technology is based on adding frequency shift keying (FSK),
alternating two sub-carriers - 424 kHz and 484 kHz.
Manchester code is used to encode data bitstream. In this mode, the data bitrates are
slightly modified. Figure 15 illustrates the way VICC transfers data to CD, using OOK. In
case of using FSK in place of OOK, the off-period of sub-carrier is replaced with sub-carrier
at 484 kHz.
The standard allows VCD and VICC to select the best conditions for the communication to
suit different operational requirements ranging from use with high RF noise at short range to
low RF noise at long range. This selection concerns modulation index, bitrates as well as
VICC-to-VCD data signaling - OOK or FSK.
Figure 15. NFC-V VICC-to-VCD data transfer
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3.5.4
Technology
Data transfer summary
Figure 16 gives a summary of different data transfer diagrams. Table 4 shows an overview
of different modulation schemes, bit coding techniques and associated frequencies and data
rates.
Table 4. NFC data transfer bit signaling, coding and rates
Data transmitter
Property
NFC-A
NFC-B
NFC-V
Frequency
13.56 MHz
13.56 MHz
13.56 MHz
Data signaling
100% ASK
modulation
10% ASK
modulation
10% or 100% ASK
modulation
Bit coding
Modified Miller
NRZ
1/4 PPM or
1/256 PPM
Data rate
106 kbit/s typ
up to 424 kbit/s(1)
106 kbit/s typ
up to 424 kbit/s
26.48 kbit/s or
or 1.65 kbit/s
Data signaling
ASK load
modulation, OOK
of sub-carrier
ASK load
modulation, BPSK
of sub-carrier
ASK load
modulation,
OOK/FSK
of sub-carrier
Sub-carrier
848 kHz
848 kHz
424/484 kHz
Bit coding
Manchester
NRZ
Manchester
Data rate
106 kbit/s typ.
up to 424 kbit/s(1)
PCD or VCD
PICC or VICC
OOK: 6.62 kbit/s
106 kbit/s typ.
or 26.48 kbit/s
up to 424 kbit/s(1) FSK: 6.67 kbit/s or
26.69 kbit/s
(1) 848 kbit/s is under validation by NFC Forum
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Figure 16. NFC data transfer summary diagram
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3.6
Technology
NFC system architecture
As many other systems, NFC technology is built over a structured logical stack of functional
layers, transiting from physical to software implementation, as depicted in Figure 17.
The lowest layers are physical - CPU, MCU infrastructure, communication interfaces and
radio-related circuitry as defined in ISO/IEC 14443-2 A and B and ISO/IEC 15693-2.
Middle layers include data packeting according to ISO/IEC 14443-3 A and B and
ISO/IEC 15693-2 and, generation of commands according to NFC-A, NFC-B, NFC-V and
NFC-F. Until this point, there is no NFC-related specificity and the system up to this point
corresponds to an RFID system. The first specificity related to NFC comes in form of middle
layers dedicated to supporting P2P communication mode. These are the logical link control
protocol (LLCP), and simple NDEP exchange protocol (SNEP), as defined in
ISO/IEC 18092. As ISO/IEC 18092 also covers one of command protocols, the NFC-F, the
LLCP and SNEP in Figure 17 are displayed at the same level.
The next higher layers of the stack, NDEF messages and NDEF records, are also NFC
specific. They are usually implemented in SW and accessed to with a user interface, the
highest layer of the NFC logical functional stack. Section 3.7 brings additional information
on NDEF.
Figure 17. NFC system functional stack
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3.7
NDEF structure
NFC data exchange format, NDEF, is one of major items that NFC standards add upon the
generic RFID. NDEF is used across all NFC devices, regardless of the underlying tag type
or NFC device technology.
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NDEF records are standardizes so NFC devices know how to interpret them. Some of
NDEF records are:

simple text record

URI

smart poster

signature

vCard (a standard electronic business card format)

pairing Bluetoothor Wi-Fi
NDEF is a light-weight binary message format designed to encapsulate application-defined
payload bearing one of more NDEF records, into a single message. NDEF records can be
of the same or of different type and the size of each of them is limited to (232-1) bytes.
NDEF message is a concatenation of NDEF records so it can be looked upon as a
paragraph bearing a discrete chunk of information and NDEF records as sentences of that
paragraph, each conveying a single piece of information. The number and size of the
sentences in the paragraph are variable.
NDEF record is made up of a header and payload. The header describes the payload with
three metadata items: payload length, payload type and, optionally, payload identifier.
3.7.1
Payload length
The payload length is a four-byte unsigned integer indicating the number of bytes in the
payload. A compact, short-record layout (one byte) is provided for very small payloads. To
efficiently detect the NDEF record boundary, the payload length is provided within the first
eight bytes of the NDEF record.
3.7.2
Payload type
The NDEF payload type identifier indicates the type of the payload. NDEF supports URIs,
MIME media type constructs and an NFC-specific type format as type identifiers. By
indicating the type of a payload, it is possible to dispatch the payload to the appropriate user
application.
3.7.3
Payload identifier
A payload may be given an optional identifier in the form of an absolute or relative URI. The
use of an identifier enables payloads that support URI linking technologies to crossreference other payloads.
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Figure 18. NDEF message structure
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Standards
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Standards
NFC technology is based on a series of standards, such as ISO/IEC 14443, ISO/IEC 15693,
ISO/IEC 18092, ECMA-340, ECMA-352 and others.
Compliance with ISO/IEC 14443A (Type A) and ISO/IEC 14443B (Type B) variants is
denoted in this document as NFC-A and NFC-B, respectively. Compliance with
JIS X 6319 4 and FELICA protocol is denoted as NFC-F. Compliance with ISO/IEC 15693 is
denoted as NFC-V, where “V” signifies vicinity - for maximum distance of operation
extended to about 1 meter. Peer-to-peer (P2P) communication mode specifically described
in ISO/IEC 18092 is denoted as P2P. NFC interface and protocol fit with ISO/IEC 18092,
ECMA-340 and ECMA-352 and is referred to as NFCIP.
The scope is to standardize the three NFC communication modes, with their protocols and
data exchange formats and bitrates. The currently defined bitrates are 106 kbit/s, 212 kbit/s,
424 kbit/s, 848 kbit/s and, within NFC-V, 1.65 kbit/s, 6.62 kbit/s (ASK with OOK), 6.67 kbit/s
(ASK with FSK), 26.48 kbit/s (ASK with OOK) and 26.69 kbit/s (ASK with FSK).
On top of standards by international standardization bodies, NFC Forum provides a number
of technical specifications of protocols, data exchange format, NFC Forum tag types, NFC
record type and more.
NFC enables smartphones to work at a basic level with legacy RFID readers. In card
emulation mode of communication, an NFC device must transmit, at minimum, a unique ID
number to a legacy reader. The NFC Forum has defined a common data format called NFC
Data Exchange Format (NDEF) that can store and transport various items. The NFC Forum
also added the Simple NDEF Exchange Protocol (SNEP) to the specification, to allow
sending and receiving messages between two NFC-enabled devices communicating in
peer-to-peer mode.
Figure 19 shows a simplified stack of layers forming the NFC technology. The upper layers
are specific to NFC while the lower layers also apply to non-NFC technologies such as
RFID.
Figure 19. Simplified stack of NFC layers
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Figure 20 shows an overview of NFC-related standards and specifications.
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Figure 20. Map of NFC-related standards and specifications
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Standards
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Standards
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Legacy ISO/IEC standards
This chapter lists standards that existed before the introduction of, and adopted by, NFC
technology. Their primary use was to standardize RFID technology.
4.1.1
ISO/IEC 14443 - Proximity cards
The standard includes four parts.
ISO/IEC 14443-1:2008 - Physical characteristics
This part of ISO/IEC 14443 standard defines the size and physical characteristics of the
card. It also lists several environmental stress conditions that the card must be capable of
withstanding without permanent damage to its operation. These tests are intended to be
performed at the card level and are dependent on the construction of the card and on the
antenna design. Most of the requirements cannot be directly translated to IC or die level.
ISO/IEC 14443-2:2015 - Radio frequency power and signal balance
This part defines the RF power and signal interface for two signaling schemes, Type A and
Type B. Both schemes are half-duplex with 106 kbit/s data rate in each direction. Data
transmitted by the card is load-modulated with 848 kHz sub-carrier. The card is powered by
the RF field. No battery is required.
ISO/IEC 14443-3:2014 - Initialization and anti-collision
This part describes the initialization and anti-collision protocols for Type-A- and Type-B
PICC. The anti-collision commands, responses, data frame and timing are defined. The
initialization and anti-collision scheme is designed so as to permit the design of multiprotocol readers capable of communicating with both Type-A- and Type-B cards. In RF field,
both card types wait silently for a polling command. A multi-protocol reader polls for one
type of card, completes any transactions with a card responding and then polls for another
type of card.
ISO/IEC 14443-4:2015 - Transmission protocol
This part defines high-level data transmission protocols for Type-A- and Type-B PICC.
These protocols are optional so PICCs may be designed with or without supporting them.
PICC reports to PCD its capability in the response to the polling command as defined in part
3 of the standard. In this way, the PCD knows whether the PICC supports high-level
protocols defined in this part of ISO/IEC 14443 standard.
Protocols defined in this part 4 also allow transferring application data units as defined in
ISO/IEC 7816-4 and application selection as defined in ISO/IEC 7816-5. ISO/IEC 7816 is
Contacted IC card standard.
4.1.2
ISO/IEC 15693 - Vicinity cards
ISO/IEC 15693 standard is member of a series of international standards that describe
contactless smartcards in vicinity area. It consists of three parts.
ISO/IEC 15693-1:2010(E)
This part of ISO/IEC 15693 standard specifies physical characteristics of vicinity cards
(VICC). It applies to identification cards of type ID-1 (specified in ISO/IEC 7810), operating
in vicinity of a coupling device.
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ISO/IEC 15693-2:2009
This part specifies the nature and characteristics of field to be provided for bi-directional
communication between vicinity coupling device (VCD) and VICC and for powering VICC
through harvesting energy from the field.
ISO/IEC 15693-3:2010
This part defines initialization and anti-collision commands interpreted by VICC and VCD.
4.2
Standards specific to NFC
NFC interface and protocol (NFCIP) is defined in ISO/IEC 18092 but also in ECMA-340 and
ECMA-352, standards of the European computer manufacturers association (ECMA). They
specify modulation schemes, coding, data rates and frame formats of the RF interface,
initialization schemes and conditions required for data anti-collision control during
initialization, for both passive and active NFC operating modes. They also define the
transport protocol, including protocol activation and data-exchange methods.
4.2.1
ISO/IEC 18092 - NFC interface and protocol 1 (NFCIP-1)
This standard defines communication modes for NFC interface and protocol (NFCIP-1),
using inductive-coupled devices operating at the center frequency of 13.56 MHz, for
interconnection of computer peripherals.
ISO/IEC 18092 also defines the active and passive operating modes of NFCIP-1 to set up a
communication network using NFC devices for networked products and for consumer
equipment.
In particular, it specifies modulation schemes, coding, transfer speeds and frame format of
the RF interface. It also describes initialization schemes and conditions required for data
anti-collision control during the initialization, as well as transport protocol including protocol
activation and data exchange methods.
ISO/IEC 18092 is aligned with ISO/IEC 13157-1:2010 (NFCIP-1 security services and
protocol) and conforms with ISO/IEC 14443-2, ISO/IEC 14443-3 and ISO/IEC 14443-4, as
well as with ISO/IEC 15693-1, ISO/IEC 15693-2 and ISO/IEC 15693-3.
4.2.2
ECMA-340: 2013 - NFC interface and protocol 1 (NFCIP-1)
This standard describes NFC interface and protocol 1 (NFCIP-1) and is compliant with
ISO/IEC 18092.
4.2.3
ECMA-352: 2013 - NFC interface and protocol 2 (NFCIP-2)
This standard describes NFC interface and protocol 2 (NFCIP-2) and is compliant with
ISO/IEC 21481.
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NFC interface ICs
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NFC interface ICs
Three main categories of NFC-dedicated peripheral ICs can serve a wide variety of NFCenabled electronic devices, ranging from simple tags through smartcards to complex
products such as smartphones. They can be called static tag IC, dynamic tag IC and P2P
interface IC.
STMicroelectronics develops and manufactures semiconductor products of each category.
5.1
Static tag IC
This type of IC ensures the operation of a static NFC tag. Static NFC tag is a passive NFC
device in the sense that, it cannot generate RF filed. Data stored in a static tag can be read
or modified by an active NFC device, such as a NFC reader or smartphone. The tag uses
load modulation to signal data to reader. Static tag can stand alone in a form of a patch, key
fob and the like or, be integrated in a bigger device, electronic or not. It can draw power from
the RF field so as to be operable without own power supply. The memory is of non-volatile
type, such as EEPROM.
Figure 21. Static tag IC
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Figure 21 shows an example of static tag IC. In STMicroelectronics product portfolio,
ST25TA is the product specifically designed and optimized for use in passive tags.
5.2
Dynamic tag IC
This type of IC allows the operation of a dynamic NFC tag. Dynamic tag is usually integrated
into an electronic device. It has the same properties and behaves the same way as a static
tag when interacting with an NFC device (a reader). On top of entirely supporting static tag
functionality, the device that the dynamic tag is integrated into also has the possibility of
reading and writing the tag’s memory contents. To enable this, a dynamic tag IC has
interfaces such as, for example, serial communication bus, to interact with an MCU on the
hosting electronic device. The read / write by the other NFC device and the read / write by
the own device’s MCU do not necessarily happen at the same moment in time. For
example, the dynamic tag contents may be modified while the tag hosting device is powered
down and the read / write by the local MCU happen when the tag hosting device is switched
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on, hours or days later. This resembles to an email communication between the external
NFC device and the MCU of the tag-hosting NFC device, where the EEPROM of the tag IC
plays the role of a mailbox.
Figure 22 gives an example of dynamic tag IC. M24LR and M24SR are STMicroelectronics
silicon ICs designed and optimized for use in dynamic tags. Optionally, a GPO/Interrupt
signal is available to wake up the microcontroller in order to optimize the power
consumption of the tag.
Figure 22. Dynamic tag IC
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5.3
P2P interface IC
The peer-to-peer (P2P) communication mode is an active NFC mode of operation requiring
two active NFC devices. Both devices also support load modulation as it is required for the
initial phase of peer-to-peer link setting. The device that first successfully accomplishes the
polling process becomes initiator and keeps that role till the end of the P2P transaction. The
other device plays the role of target.
Once the communication link is established, the peers maximize the use of direct
modulation and alternatively generate RF field and transmit data then switch off RF field and
receive data from the other peer. This resembles to a live human discussion as it
necessarily happens at the same moment in time. Using the direct field modulation allows
achieving higher communication speeds and efficiency. An interface IC allowing P2P
communication mode needs to support, on top of dynamic tag IC functionality, own RF field
generation and provide physical assets, such as RAM buffer.
Devices like smartphone that need to support P2P mode, make use of this kind of NFC
interface IC that can also fulfill the requirements for dynamic and static tag interface IC.
Figure 23 shows typical architectural blocks of an NFC P2P interface IC. Among
STMicroelectronics silicon IC products, ST95HF fulfills requirements for a NFC P2P
interface. Optionally, a GPO/Interrupt signal is available to wake up the microcontroller in
order to optimize the power consumption of the system.
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NFC interface ICs
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Figure 23. P2P interface IC
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Conclusion
Conclusion
The goal of this document is to provide readers with basic information on NFC technology,
underlining its potential to be part of Internet of Things, a network of devices and systems
bringing user value through their interconnection.
The document further helps readers orient themselves in the landscape of standards that
govern NFC technology. Upon reading, they should be able to take right decisions as to
purchasing copies of standards they need to understand in detail for their NFC-related
project.
The document also highlights some of ST products enabling NFC electronic devices. For
more information, readers can check www.st.com or contact STMicroelectronics local sales
office.
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Revision history
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Revision history
Table 5. Document revision history
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Date
Revision
22-Jun-2015
1
Changes
Initial release.
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