ECMA-373 2nd Edition / June 2012
Near Field Communication Wired Interface (NFC-WI)
Reference number ECMA-123:2009
© Ecma International 2009
COPYRIGHT PROTECTED DOCUMENT
© Ecma International 2012
Contents
Page
1
Scope ...................................................................................................................................................... 1
2
Conformance ......................................................................................................................................... 1
3
Normative references ............................................................................................................................ 1
4
Terms and definitions ........................................................................................................................... 1
5 5.1 5.2 5.3 5.4
Conventions and notations .................................................................................................................. 1 Representation of bit values ................................................................................................................ 1 Representation of logical states of LOW and HIGH ........................................................................... 1 Capitalisation of names ........................................................................................................................ 2 State notation ......................................................................................................................................... 2
6
Acronyms ............................................................................................................................................... 2
7
General ................................................................................................................................................... 2
8 8.1 8.1.1 8.1.2 8.2 8.3
Signals .................................................................................................................................................... 3 Signal wires ............................................................................................................................................ 3 Signal-In ................................................................................................................................................. 3 Signal-Out .............................................................................................................................................. 3 Electrical characteristics ...................................................................................................................... 3 Clock frequency (fCLK) ........................................................................................................................... 4
9 9.1 9.2 9.2.1 9.2.2 9.3 9.3.1 9.3.2 9.4 9.4.1 9.4.2 9.5 9.5.1
NFC-WI states ........................................................................................................................................ 4 Off state .................................................................................................................................................. 5 Activating state ...................................................................................................................................... 5 Signal-Out activation............................................................................................................................. 6 Signal-In activation................................................................................................................................ 6 On state .................................................................................................................................................. 7 Idle........................................................................................................................................................... 8 Busy ........................................................................................................................................................ 8 De-Activating state ................................................................................................................................ 8 Signal-Out deactivation ........................................................................................................................ 9 Signal-In deactivation ........................................................................................................................... 9 Command state...................................................................................................................................... 9 Escape sequence .................................................................................................................................. 9
10 10.1 10.2 10.3 10.3.1 10.3.2 10.4 10.4.1 10.4.2 10.5
Information-Transfer ........................................................................................................................... 10 Manchester Bit coding ........................................................................................................................ 10 Modified Miller Bit coding ................................................................................................................... 10 Bit coding for fCLK/128 (~106 kb/s) ..................................................................................................... 11 Signal-Out ............................................................................................................................................ 11 Signal-In ............................................................................................................................................... 11 Bit coding for fCLK/64 (~212 kb/s) ....................................................................................................... 11 Signal-Out ............................................................................................................................................ 11 Signal-In ............................................................................................................................................... 12 Bit coding for fCLK/32 (~424 kb/s) ....................................................................................................... 12
Annex A (informative) Application of NFC-WI with NFCIP-1 ........................................................................ 13 A.1 General ................................................................................................................................................. 13 A.2 Reference ............................................................................................................................................. 13 A.3 Propagation delay ............................................................................................................................... 13 A.4 Communication Mode ......................................................................................................................... 13 A.5 RF-field control during activation ...................................................................................................... 13 A.5.1 Activation without RF-field ................................................................................................................. 13
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A.5.2 A.6 A.6.1 A.6.2
Activation with RF-field .......................................................................................................................14 Signal diagrams ...................................................................................................................................15 fCLK/128 ..................................................................................................................................................15 fCLK/64 ....................................................................................................................................................16
Annex B (informative) Command state ...........................................................................................................17 B.1 Configuration .......................................................................................................................................17
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Introduction Following the standardisation of Near Field Communication (NFC) systems and their test methods in Ecma International, this Standard specifies a two-wire interface between two components called “Transceiver” and “Front-end”. Systems that implement the NFC-WI interface can thus be augmented with e.g. a wireless Front-end for NFCIP-1 as illustrated in Figure 1. Although this Standard only specifies requirements for the Signal-In and Signal-Out wires and the digital signals they carry, informative Annex A lists some NFCIP-1 specific considerations.
NFC Wired Interface (NFC-WI)
NFC Transceiver
Signal-Out
NFC Front-End
Device (e.g. NFCIP-1)
Signal-In
Out of Scope
Out of Scope In scope
Figure 1 — Context diagram for the NFC wired interface This 2nd edition is fully aligned with the 1st edition of ISO/IEC 28361:2007.
This Ecma Standard has been adopted by the General Assembly of June 2012.
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© Ecma International 2012
Near Field Communication Wired Interface (NFC-WI)
1
Scope
This Standard specifies the digital wire interface between a Transceiver and a Front-end. The specification includes the signal wires, binary signals, the state diagrams and the bit encodings for three data rates.
2
Conformance
Conformant Transceivers and Front-ends implement the wired interface specified herein.
3
Normative references
None.
4
Terms and definitions
For the purposes of this document, the following terms and definitions apply. 4.1 Clock sequence of LOW and HIGH as defined in 5.2 with duration of 1/(2*fCLK), where fCLK is the clock frequency as defined in 8.3 4.2 Information Bit-coded data as defined in Clause 10 4.3 Front-end entity that drives the Signal-Out wire and receives on the Signal-In wire 4.4 Transceiver entity that drives the Signal-In wire and receives on the Signal-Out wire
5
Conventions and notations
5.1
Representation of bit values
Bit values are either ZERO or ONE.
5.2
Representation of logical states of LOW and HIGH
⎯ The logical signal state is LOW if the electrical level of a signal has the input voltage of VIL or the output voltage of VOL as specified in Table 1 in 8.2.
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⎯ The logical signal state is HIGH if the electrical level of a signal has the input voltage of VIH or the output voltage of VOH as specified in Table 1 in 8.2.
5.3
Capitalisation of names
The initial character of names of basic elements, e.g. specific fields, is capitalised.
5.4
State notation
The states are specified in Unified Modelling Language (UML) notation.
6 Acronyms AND
Logical AND operation
fCLK
Clock frequency as defined in 8.3
NFC-WI
Near Field Communication Wired Interface
OR
Logical OR operation
XOR
Logical XOR operation
÷
Divide a clock frequency by a constant value.
Table 1 in 8.2 lists additional symbols for electrical characteristics.
7
General
The NFC-Wired Interface (NFC-WI) specifies the Signal-In and the Signal-Out wires as illustrated in Figure 2. The wires carry binary signals of HIGH and LOW. NFC Wired Interface (NFC-WI)
NFC Transceiver
Signal-Out
NFC Front-End
Signal-In
In scope
Figure 2 — NFC-WI The combinations of the signals on the wires make up the NFC-WI states as defined in Clause 9. Clause 10 specifies encodings for Information transfer, while in the On state, for the fCLK/128, fCLK/64 and fCLK/32 data transfer rates. Annex A lists NFCIP-1 specific considerations for implementing the NFC-WI; Annex B lists possible uses of the Command state, such as changing to alternative protocols.
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Signals
8.1 Signal wires 8.1.1
Signal-In
The Transceiver drives the Signal-In wire with a binary signal of HIGH and LOW. The Front-end receives the binary signal on Signal-In. 8.1.2
Signal-Out
The Front-end drives the Signal-Out wire with a binary signal of HIGH and LOW. The Transceiver receives the binary signal on Signal-Out.
8.2
Electrical characteristics
The wires shall carry (binary) digital signals as illustrated in Figure 3 and specified in Table 1.
Figure 3 — Illustration of some electrical parameters
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Table 1 — Electrical characteristics Symbol Parameter
Conditions
Min
Max
Unit
DC Characteristics VS
Signalling voltage amplitude
Not applicable
1,62
3,63
V
VIH
HIGH level input voltage
Not applicable
1,10
3,63
V
VIL
LOW level input voltage
Not applicable
0
0,70
V
ILI
Input leakage current
Input voltage is between VILmin and VIHmax
±4
mA
VOH
HIGH level output voltage
Driver source current of 4mA
1,32
3,63
V
VOL
LOW level output voltage
Driver sink current of 4mA
0
0,30
V
AC Characteristics tr
Signal-In, Signal-Out rise (from 10 % to 90 % of VS)
time Add an external capacitive load between 10 pF and 30 pF for testing
4
20
ns
tf
Signal-In, Signal-Out fall (from 90 % to 10 % of VS)
time Add an external capacitive load between 10 pF and 30 pF for testing
4
20
ns
tSP
Pulse width of spikes and glitches which must be suppressed by the Not applicable input filter
1
ns
CI
Input capacitance
10
pF
CL
External load capacitance for the Not applicable driver
30
pF
VITR
Input voltage transitions
3,93
V
range
1 MHz test frequency
at
signal
Pulse width
Not applicable
– 0,30
Not applicable
30
Not applicable
20
ns
Environmental / Test Conditions Tamb
Ambient temperature for electrical characteristics measurements
26
°C
8.3 Clock frequency (fCLK) The clock frequency (fCLK) shall be 13,56 MHz ± 7 kHz.
9
NFC-WI states
Figure 4 specifies the main NFC-WI states. The Off state and the On state are the main NFC-WI states. The Off state is the default state. NFC-WI shall move from the Off state to the On state as specified in 9.2. NFC-WI shall move from the On state to the Off state as specified in 9.4.
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NFC-WI shall move from the On state to the Command state via the Escape sequence.
Off
Activating
Deactivating
On
Command
Figure 4 — Main states of NFC-WI
9.1 Off state When Signal-In and Signal-Out are LOW for at least 120 µs, the NFC-WI state shall be Off. NOTE
In this state, power saving features may be implemented.
9.2 Activating state The NFC-WI shall enter the Activating state when either Signal-Out or Signal-In carry the activation sequence, as specified in 9.2.1 and 9.2.2 respectively. When subsequently the opposite wire carries the activation response, the NFC-WI shall enter the On state, as shown in Figure 5.
Activating
ACT_REQ_So
Wait SignalIn
ACT_RES_Si
ACT_REQ_Si
ACT_RES_So
Wait SignalOut
Figure 5 — Activating state
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9.2.1
Signal-Out activation
When the Signal-Out wire carries the ACT_REQ_So, the NFC-WI shall enter the Activating state. When Signal-In carries the ACT_RES_Si no later than 50 ms after entering the Activating state the NFC-WI shall enter the On state. Otherwise the NFC-WI shall enter the Off state. The activation sequence is illustrated in Figure 6 and Figure 7. Transceiver
Front-end ACT_REQ_So
ACT_RES_Si
Figure 6 — Signal-Out activation
9.2.1.1
ACT_REQ_So
The Clock on the Signal-Out wire constitutes the ACT_REQ_So as illustrated in the upper part of Figure 7. 9.2.1.2
ACT_RES_Si
The HIGH on Signal-In constitutes the ACT_RES_Si as illustrated in the lower part of Figure 7.
Off State
Activating State
On State
HIGH Signal on Signal-Out LOW t HIGH Signal on Signal-In LOW max. 50ms
t
Figure 7 — Signal-Out initiated activation sequence
9.2.2
Signal-In activation
When the Signal-In wire carries the ACT_REQ_Si, the NFC-WI shall enter the Activating state. When SignalOut carries the ACT_RES_So within a period of between 100 µs and 50 ms after entering the Activating state the NFC-WI shall enter the On state. Otherwise the NFC-WI shall enter the Off state.
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The activation sequence is illustrated in Figure 8 and Figure 9. Transceiver
Front-end ACT_REQ_Si
ACT_RES_So
Figure 8 — Signal-In activation
9.2.2.1
ACT_REQ_Si
At least 127 pulses with a frequency in the range of 2 MHz to 12 MHz on Signal-In constitute the ACT_REQ_Si as illustrated in the upper part of Figure 9. Subsequently Signal-In shall be HIGH. 9.2.2.2
ACT_RES_So
The Clock on the Signal-Out wire constitutes the ACT_RES_So as illustrated in the lower part of Figure 9.
Off State
Activating State
On State
HIGH Signal on Signal-In LOW t HIGH Signal on Signal-Out LOW t 100µs .. 50ms
Figure 9 — Signal-In initiated activation sequence
9.3 On state The On state consists of the Idle and Busy sub states; Idle is the default sub-state of On, as shown in Figure 10.
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On
Idle
Busy
Figure 10 — The On state 9.3.1
Idle
While in the On state, in the absence of Information-transfer, the On sub-state shall be Idle. In the Idle substate, Signal-In shall carry HIGH, and Signal-Out shall carry the Clock. 9.3.2
Busy
While in the On state, during Information-transfer on either Signal-In or Signal-Out, the On sub-state shall be Busy.
9.4 De-Activating state The NFC-WI shall enter the De-Activating state when either Signal-Out or Signal-In carry the deactivation sequence as specified in 9.4.1 and 9.4.2 respectively. When subsequently the opposite wire carries the deactivation response, the NFC-WI shall enter the Off state, see Figure 11.
D e-A ctivating
D E A C _ R E Q _S o
W ait S ignalIn
D E A C _R E Q _ S i
D E A C _ R E S _S i D E A C _ R E S _S o
W ait S ignalO ut
Figure 11 — De-Activating state
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9.4.1
Signal-Out deactivation
When Signal-Out carries DEACT_REQ_So, the NFC-WI shall enter De-Activating state. Within 50 ms, the Signal-In shall carry DEACT_RES_Si, and the NFC-WI shall enter the Off state. 9.4.1.1
DEACT_REQ_So
Signal-Out set to LOW for more than 120 µs constitutes the DEACT_REQ_So. 9.4.1.2
DEACT_RES_Si
Signal-In set to LOW constitutes the DEACT_RES_Si. 9.4.2
Signal-In deactivation
When Signal-In carries DEACT_REQ_Si, the NFC-WI shall enter De-Activating state. Within 50 ms, the Signal-Out shall carry DEACT_RES_So, and the NFC-WI shall enter the Off state. 9.4.2.1
DEACT_REQ_Si
Signal-In set to LOW for more than 120 µs constitutes the DEACT_REQ_Si. 9.4.2.2
DEACT_RES_So
Signal-Out set to LOW constitutes the DEACT_RES_So.
9.5 Command state The Command state shall be entered from the On state using the Escape sequence. The default bit coding in Command state shall be as defined in 10.3, Bit coding for fCLK/128. The Command state is exited with a command. The command set is outside the scope of this Standard. 9.5.1
Escape sequence
At least 127 pulses with a frequency in the range from 2 MHz to 12 MHz on Signal-In constitute the Escape sequence as illustrated in Figure 12. Subsequently Signal-In shall be HIGH.
On State
Command State
HIGH Signal on Signal-In LOW t HIGH Signal on Signal-Out LOW t
Figure 12 — Escape sequence
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10 Information-Transfer This Clause specifies the bit coding for three data rates.
10.1 Manchester Bit coding The Manchester bit coding encodes ONE and ZERO in a LOW to HIGH transition in the middle of a bit period as illustrated in Figure 13. The first half of the bit is HIGH and the second half of the bit is LOW for a ONE. The first half of the bit is LOW and the second half of the bit is HIGH for a ZERO. Reverse polarity shall be permitted.
Figure 13 — Manchester bit coding
10.2 Modified Miller Bit coding The Modified Miller bit coding defines ONE and ZERO by the position of a pulse during one bit period. The pulse is a transition from HIGH to LOW, followed by a period of LOW, followed by a transition to HIGH. The bit representation is illustrated in Figure 14. For a ONE the pulse shall occur in the second half of the bit period; the transition from HIGH to LOW shall be in the middle of the bit period. For a ZERO a pulse shall occur at the beginning of the bit period with the following exception. In case a ZERO bit follows a ONE bit, no pulse shall occur during this ZERO.
Figure 14 — Modified Miller bit coding The jitter margin for the rising pulse edge is +/- 2/fc. NOTE
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For implementation recommendations the propagation delays as specified in A.3 should be respected.
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10.3 Bit coding for fCLK/128 (~106 kb/s) 10.3.1 Signal-Out Signal-Out shall carry the AND combination of the Modified Miller bit coded data and fCLK as illustrated in Figure 15. The Modified Miller bit coded pulse is at least 7 and at most 45 fCLK cycles long.
Bit value
ZERO
ZERO
ONE
ONE
ZERO
ZERO
HIGH
Signal on Signal-Out LOW t
Figure 15 — Signal-Out coding at fCLK/128
10.3.2 Signal-In Coding on Signal-In shall carry the OR combination of the inverted Manchester bit-coded data and (fCLK÷16). Every bit shall start with the low phase of the (fCLK÷16) as illustrated in Figure 16.
Bit value
ONE
ZERO
ONE
ONE
HIGH
Signal on Signal-In LOW t
Figure 16 — Signal-In coding at fCLK/128
10.4 Bit coding for fCLK/64 (~212 kb/s) 10.4.1 Signal-Out Signal-Out shall carry the XOR of the Manchester bit-coded data and the Clock, as illustrated in Figure 17.
Bitvalue
ZERO
ONE
ZERO
ZERO
ONE
HIGH Signal on Signal-Out
LOW
t
Figure 17 — Signal-Out coding at fCLK/64
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10.4.2 Signal-In Coding on Signal-In shall carry the Manchester bit-coded data, as illustrated in Figure 18.
Bit value
ZERO
ONE
ZERO
ONE
ONE
HIGH
Signal on Signal-In LOW t
Figure 18 — Signal-In coding at fCLK/64
10.5 Bit coding for fCLK/32 (~424 kb/s) The bit coding for fCLK/32 shall be the same as the bit coding for fCLK/64 as defined in 10.4.
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Annex A (informative) Application of NFC-WI with NFCIP-1
A.1 General This Annex lists specific considerations for NFCIP-1 devices that implement NFC-WI.
A.2 Reference ECMA-340
Near Field Communication - Interface and Protocol (NFCIP-1)
A.3 Propagation delay The propagation delay of the Front-end is the integer number of clock cycles needed for signal processing in the Front-end. This delay is divided into two parts, one time for Signal-Out (t1) and one for Signal-In (t2). The sum of them is the propagation delay. ECMA-340 Front-ends, using the NFC-WI interface have the following requirements on the propagation delay: For data rate fCLK/128:
(t1 + t2) equal to 128 clock cycles
For data rate fCLK/64:
(t1 + t2) maximum 256 clock cycles
For data rate fCLK/32:
(t1 + t2) maximum 256 clock cycles
A.4 Communication Mode The default communication mode is the Passive communication mode.
A.5 RF-field control during activation In 9.2, the Standard defines the Activating state. The activation sequence defined in 9.2.2 only activates the NFC-WI. Whether the NFCIP-1 RF-field is switched on is described by the following two cases.
A.5.1 Activation without RF-field When ACT_REQ_Si is shorter than 100µs the NFC-WI enters the On state without the Front-end switching on the RF-field.
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Off State
Activating State
On State
HIGH Signal on Signal-In LOW t HIGH Signal on Signal-Out LOW t < 100µs
Max RF-field Min t
Figure A.1 — Activation without RF-field
A.5.2 Activation with RF-field When ACT_REQ_Si is overlapping the ACT_RES_So for at least 16 clock cycles the NFC-WI enters the On state with the Front-end performing the Initial RF collision avoidance sequence as defined in ECMA-340. If the Front-end is not able to switch on the RF-field it initiates the Signal-Out deactivation.
Off State
Activating State
On State
HIGH Signal on Signal-In LOW t HIGH Signal on Signal-Out LOW t 100µs .. 50ms
> 16 clock cycles
Max RF-field Min t
Figure A.2 — Activation with RF-field
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A.6 Signal diagrams This Clause illustrates possible signal combinations for Signal-In, Signal-Out and the RF-field.
A.6.1 fCLK/128
HIGH RF-field LOW t OFF State
ACTIVATING State
ON State IDLE sub-state
BUSY sub-state
IDLE sub-state
BUSY sub-state
IDLE sub-state
DEACTIVATING State
OFF State
HIGH Signal-out wire LOW t HIGH Signal-in wire LOW t max. 50ms
t1
t2
Figure A.3 — Signal diagram fCLK/128
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A.6.2 fCLK/64
HIGH RF-field LOW t OFF State
ACTIVATING State
ON State IDLE sub-state
BUSY sub-state
IDLE sub-state
BUSY sub-state
IDLE sub-state
DEACTIVATING State
OFF State
HIGH Signal-out wire LOW t HIGH Signal-in wire LOW t max. 50ms
t1
t2
Figure A.4 — Signal diagram fCLK/64
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Annex B (informative) Command state
B.1 Configuration This Standard specifies the Escape sequence to enter the Command state in 9.5. The Command state allows the exchange of control and state information between the Transceiver and the Front-end. Such exchange may include: indication of the presence of the RF-field; information about the state of the RFCollision avoidance; control information to change data rates and communication modes. Furthermore, the Command mode allows changing to other communication protocols.
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