ISO/IEC 7816-3:2006

INTERNATIONAL ISO/IEC
STANDARD 7816-3
Third edition
2006-11-01
Identification cards — Integrated circuit
cards —
Part 3:
Cards with contacts — Electrical
interface and transmission protocols
Cartes d'identification — Cartes à circuit intégré —
Partie 3: Cartes à contacts — Interface électrique et protocoles
de transmission
Reference number
©
ISO/IEC 2006
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©  ISO/IEC 2006
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ii © ISO/IEC 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols and abbreviated terms . 3
5 Electrical characteristics . 5
5.1 General. 5
5.2 Contacts. 6
6 Card operating procedure. 9
6.1 Principles. 9
6.2 Activation, resets and class selection. 9
6.3 Information exchange. 11
6.4 Deactivation. 12
7 Asynchronous character . 13
7.1 Elementary time unit. 13
7.2 Character frame . 13
7.3 Error signal and character repetition. 14
8 Answer to reset . 15
8.1 Characters and coding conventions. 15
8.2 Answer-to-Reset . 16
8.3 Global interface bytes . 18
9 Protocol and parameters selection. 20
9.1 PPS exchange . 20
9.2 PPS request and response . 20
9.3 Successful PPS exchange . 21
10 Protocol T=0, half-duplex transmission of characters . 22
10.1 Scope . 22
10.2 Character level . 22
10.3 Structure and processing of commands. 22
11 Protocol T=1, half-duplex transmission of blocks . 24
11.1 Scope and principles. 24
11.2 Character frame . 24
11.3 Block frame . 24
11.4 Protocol parameters. 27
11.5 Character component operation at data link layer. 28
11.6 Block component operation at data link layer. 28
12 Transmission of command-response pairs . 32
12.1 Application protocol data units. 32
12.2 Command-response pair transmission by T=0 . 34
12.3 Command-response pair transmission by T=1 . 40
Annex A (informative) Scenarios for T=1. 42
Bibliography . 50

© ISO/IEC 2006 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
ISO/IEC 7816-3 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 17, Cards and personal identification.
This third edition cancels and replaces the second edition (ISO/IEC 7816-3:1997), which has been technically
revised. It also incorporates the Amendment ISO/IEC 7816-3:1997/Amd.1:2002.
In addition, it incorporates material extracted from the first edition of Part 4 (ISO/IEC 7816-4:1995), so that the
transmission protocols are no longer present in the second edition of Part 4 (ISO/IEC 7816-4:2005).
ISO/IEC 7816 consists of the following parts, under the general title Identification cards — Integrated circuit
cards:
⎯ Part 1: Cards with contacts — Physical characteristics
⎯ Part 2: Cards with contacts — Dimensions and location of the contacts
⎯ Part 3: Cards with contacts — Electrical interface and transmission protocols
⎯ Part 4: Organization, security and commands for interchange
⎯ Part 5: Registration of application providers
⎯ Part 6: Interindustry data elements for interchange
⎯ Part 7: Interindustry commands for Structured Card Query Language (SCQL)
⎯ Part 8: Commands for security operations
⎯ Part 9: Commands for card management
⎯ Part 10: Cards with contacts — Electronic signals and answer to reset for synchronous cards
⎯ Part 11: Personal verification through biometric methods
⎯ Part 12: Cards with contacts — USB electrical interface and operating procedures
⎯ Part 13: Commands for application management in multi-application environment
⎯ Part 15: Cryptographic information application
iv © ISO/IEC 2006 – All rights reserved

Introduction
ISO/IEC 7816 is a series of standards specifying integrated circuit cards and the use of such cards for
interchange. These cards are identification cards intended for information exchange negotiated between the
outside world and the integrated circuit in the card. As a result of an information exchange, the card delivers
information (computation result, stored data), and/or modifies its content (data storage, event memorization).
Five parts are specific to cards with galvanic contacts and three of them specify electrical interfaces.
⎯ ISO/IEC 7816-1 specifies physical characteristics for cards with contacts.
⎯ ISO/IEC 7816-2 specifies dimensions and location of the contacts.
⎯ ISO/IEC 7816-3 specifies electrical interface and transmission protocols for asynchronous cards.
NOTE The first and second editions of ISO/IEC 7816-3 specified an optional use of contact C6 to provide the
card with programming power required to write or to erase internal non-volatile memory. As every card manufactured
since 1990 internally generates programming power, this third edition deprecates this use, as well as the related
indications in the Answer-to-Reset and the related controls in each transmission protocol.
⎯ ISO/IEC 7816-10 specifies electrical interface and answer to reset for synchronous cards.
⎯ ISO/IEC 7816-12 specifies electrical interface and operating procedures for USB cards.
All the other parts are independent of the physical interface technology. They apply to cards accessed by one
or more of the following methods: contacts, close coupling and radio frequency.
⎯ ISO/IEC 7816-4 specifies organization, security and commands for interchange.
⎯ ISO/IEC 7816-5 specifies registration of application providers.
⎯ ISO/IEC 7816-6 specifies interindustry data elements for interchange.
⎯ ISO/IEC 7816-7 specifies commands for structured card query language.
⎯ ISO/IEC 7816-8 specifies commands for security operations.
⎯ ISO/IEC 7816-9 specifies commands for card management.
⎯ ISO/IEC 7816-11 specifies personal verification through biometric methods.
⎯ ISO/IEC 7816-13 specifies commands for application management in multi-application environment.
⎯ ISO/IEC 7816-15 specifies cryptographic information application.
[3] [5] [6]
ISO/IEC 10536 specifies access by close coupling. ISO/IEC 14443 and ISO/IEC 15693 specify access by
radio frequency. Such cards are also known as contactless cards.

© ISO/IEC 2006 – All rights reserved v

ISO and IEC draw attention to the fact that it is claimed that compliance with this document may involve the
use of patents.
ISO and IEC take no position concerning the evidence, validity and scope of these patent rights.
The holders of these patent rights have assured ISO and IEC that they are willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect,
the statements of the holders of these patent rights are registered with ISO and IEC. Information may be
obtained from the following companies.
Patent holder Patent number Details Foreign equivalents
FRA 8708646,
Integrated circuit card,
FRA 8717770,
JPN 2537199 (priority date: 1986-06-20;
USA 4833595,
publication date: 1996-07-08)
USA 4901276
Toshiba Corporation
Intellectual Property Division
Processing system which
1-1, Shibaura 1-Chome
transmits a predetermined
Minato-ku, Tokyo
error code upon detection of
FRA 8713306,
105-8001, Japan
USA 5161231 an incorrect transmission
FRA 9209880
code,
(priority date: 1991-03-12;
publication date: 1992-11-03)
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those identified above. ISO and IEC shall not be held responsible for identifying any or all
such patent rights.
vi © ISO/IEC 2006 – All rights reserved

INTERNATIONAL STANDARD ISO/IEC 7816-3:2006(E)

Identification cards — Integrated circuit cards —
Part 3:
Cards with contacts — Electrical interface and transmission
protocols
1 Scope
This part of ISO/IEC 7816 specifies the power and signal structures, and information exchange between an
integrated circuit card and an interface device such as a terminal.
It also covers signal rates, voltage levels, current values, parity convention, operating procedure, transmission
mechanisms and communication with the card.
It does not cover information and instruction content, such as identification of issuers and users, services and
limits, security features, journaling and instruction definitions.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/IEC 7816-2, Identification cards — Integrated circuit cards — Part 2: Cards with contacts — Dimensions
and location of the contacts
ISO/IEC 7816-4, Identification cards — Integrated circuit cards — Part 4: Organization, security and
commands for interchange
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
block
byte string comprising two or three fields defined as prologue field, information field and epilogue field
3.2
class of operating conditions
set of values for voltage and current
3.3
cold reset
first reset occurring after activation
3.4
destination node address
portion of the node address byte, identifying the intended receiver of the block
© ISO/IEC 2006 – All rights reserved 1

3.5
elementary time unit
nominal duration of a moment within an asynchronous character
3.6
epilogue field
final field of a block, conveying the error detection code
3.7
identification card
card identifying its holder and issuer, which may carry data required as input for the intended use of the card
and for transactions based thereon
[2]
[ISO/IEC 7810 ]
3.8
information block
block whose primary purpose is to convey application layer information
3.9
information field
field of a block, conveying data, generally application data
3.10
interface device
terminal, communication device or machine to which the card is electrically connected during operation
3.11
length byte
portion of the prologue field, encoding the number of bytes in the information field of the block
3.12
node address byte
portion of the prologue field, indicating both destination and source addresses of the block
3.13
operating card
card that can correctly carry out all its functions
3.14
procedure byte
byte transmitted by the card for indicating the progression of a T=0 command and controlling the exchange of
data bytes
3.15
prologue field
first field of a block, consisting of three bytes defined as node address, protocol control and length
3.16
protocol control byte
portion of the prologue field, encoding transmission control information
3.17
receive ready block
block conveying the send-sequence number of the expected I-block, used as a positive or negative
acknowledgment
3.18
redundancy code
content of the epilogue field, computed from all the bytes in the prologue field and in the information field
2 © ISO/IEC 2006 – All rights reserved

3.19
source node address
portion of the node address byte, identifying the transmitter of the block
3.20
supervisory block
block conveying transmission control information
3.21
transmission control
function used to control the data transmission between the interface device and the card, including block
transmission with sequence control, synchronization and recovery of transmission errors
3.22
warm reset
any reset that is not a cold reset
4 Symbols and abbreviated terms
For the purposes of this document, the following symbols and abbreviated terms apply.
A, B, C classes of operating conditions
APDU application protocol data unit
BGT block guard time
BWI block waiting time integer
BWT block waiting time
CGT character guard time
C input capacitance
IN
CLA class byte
CLK clock contact
C output capacitance
OUT
CRC cyclic redundancy code
CWI character waiting time integer
CWT character waiting time
(C(6) C(7)) value of the concatenation of bytes C(6) and C(7) (the first byte is the most significant byte)
D baud rate adjustment integer
DAD destination node address
Dd, Di, Dn default values, indicated values and negotiated values of D
etu elementary time unit
F clock rate conversion integer
f frequency value of the clock signal provided to the card by the interface device
Fd, Fi, Fn default values, indicated values and negotiated values of F
GND ground contact
GT guard time
© ISO/IEC 2006 – All rights reserved 3

H high state
I-block information block
I current at VCC
CC
IFS maximum information field size
IFSC IFS for the card
IFSD IFS for the interface device
I high level input current
IH
I low level input current
IL
INF information field
INS instruction byte
I high level output current
OH
I low level output current
OL
I/O input/output contact
L low state
L field length field for coding number N
c c
L field length field for coding number N
e e
LEN length byte
LRC longitudinal redundancy code
N extra guard time integer
NAD node address byte
N exact number of available data bytes
a
N number of bytes in the command data field
c
N maximum number of bytes expected in the response data field
e
N number of remaining data bytes
m
N number of bytes in the response data field
r
N number of extra data bytes still available
x
OSI open systems interconnection
PCB protocol control byte
PPS protocol and parameters selection
P1 P2 parameter bytes
R-block receive ready block
RFU reserved for future use
RST reset contact
SAD source node address
S-block supervisory block
SPU standard or proprietary use contact
4 © ISO/IEC 2006 – All rights reserved

state H high electrical level
state L low electrical level
SW1 SW2 status bytes
T type
T=0 half duplex transmission of characters
T=1 half duplex transmission of blocks
TA, TB, … interface bytes
TCK check character
t fall time, from 90 % to 10 % of signal amplitude
F
TPDU transmission protocol data unit
t rise time, from 10 % to 90 % of signal amplitude
R
TS initial character
T0 format byte
T , T , … historical bytes
1 2
U voltage at VCC
CC
U high level input voltage
IH
U low level input voltage
IL
U high level output voltage
OH
U low level output voltage
OL
[1]
NOTE In accordance with ISO 31 , the symbols U , U , U , U and U replace the former symbols V , V , V ,
CC IH IL OH OL CC IH IL
V and V .
OH OL
VCC supply power contact
WI waiting time integer
WT waiting time
WTX waiting time extension
X clock stop indicator
Y class indicator
'XY' notation using the hexadecimal digits '0' to '9' and 'A' to 'F', equal to XY to the base 16
5 Electrical characteristics
5.1 General
5.1.1 Contact assignment
The dimensions and location of the contacts shall be as specified in ISO/IEC 7816-2.
© ISO/IEC 2006 – All rights reserved 5

This part of ISO/IEC 7816 supports at least the following contacts.
⎯ C1: supply power input (VCC, see 5.2.1).
⎯ C2: reset signal input (RST, see 5.2.2).
⎯ C3: clock signal input (CLK, see 5.2.3).
⎯ C5: ground (GND, reference voltage).
⎯ C6: standard or proprietary use (SPU, see 5.2.4).
⎯ C7: input/output for serial data (I/O, see 5.2.5).
NOTE This document deprecates the use of contact C6 to provide the card with programming power because every
card manufactured since 1990 internally generates programming power.
5.1.2 Measurement conventions
By definition, when a card and an interface device are mechanically connected, each contact of the card and
the corresponding contact of the interface device together form an “electrical circuit”.
All measurements on an electrical circuit are defined with respect to GND and in an ambient temperature
range 0° C to 50° C. All currents flowing into the card are considered positive. All timings shall be measured
with respect to the appropriate threshold levels.
By definition, an electrical circuit is “not active” when the voltage with respect to GND remains between 0 V
and 0,4 V for currents less than 1 mA flowing into the interface device.
5.1.3 Classes of operating conditions
This document defines three classes of operating conditions, based on the nominal supply voltage provided to
the card by the interface device through VCC.
⎯ 5 V for class A.
⎯ 3 V for class B.
⎯ 1,8 V for class C.
The card shall support one or more classes. If the interface device applies a class supported by the card, then
the card shall operate as specified.
⎯ If the card supports more than one class, those classes shall be consecutive.
⎯ If the interface device offers more than one class, the order in which those classes are applied is not
within the scope of this document.
No card shall be damaged when the interface device applies a class not supported by the card (by definition,
a damaged card no longer operates as specified or contains corrupt data).
5.2 Contacts
5.2.1 VCC (C1)
This contact is used to supply the card with power.
6 © ISO/IEC 2006 – All rights reserved

Table 1 — Electrical characteristics of VCC under normal operating conditions
Symbol Conditions Minimum Maximum Unit
Class A 4,5 5,5
U Class B 2,7 3,3 V
CC
Class C  1,62  1,98
Class A, at maximum allowed frequency 60
I Class B, at maximum allowed frequency 50 mA
CC
Class C, at maximum allowed frequency 30
When the clock is stopped, see 6.3.2   0,5
The current value is averaged over 1 ms.

The maximum current is defined for the card. The interface device shall be able to deliver this current within
the range specified for the voltage value and may deliver more. The supply power shall maintain the voltage
value within the specified range despite transient power consumption as defined in Table 2.
Table 2 — Spikes on I
CC
a b
Class Maximum charge Maximum duration Maximum variation of I
CC
A 20 nA.s 400 ns 100 mA
B 10 nA.s 400 ns  50 mA
C  6 nA.s 400 ns  30 mA
a
The maximum charge is half the product of the maximum duration and the maximum variation.
b
The maximum variation is the difference in supply current with respect to the average value.

5.2.2 RST (C2)
This contact is used to provide the card with reset signal. See 6.2.2 (cold reset) and 6.2.3 (warm reset).
Table 3 — Electrical characteristics of RST under normal operating conditions
Symbol Conditions Minimum Maximum Unit
U 0,8 U U V
IH CC CC
I U –20 +150 µA
IH IH
U 0 0,12 U V
IL CC
I U –200 +20 µA
IL IL
t t C = 30 pF 1 µs
R F IN
The voltage shall remain between – 0,3 V and U + 0,3 V.
CC
5.2.3 CLK (C3)
This contact is used to provide the card with clock signal. The actual value of the frequency of the clock signal
is denoted f. The minimum value shall be 1 MHz. At least during activation (see 6.2.1) and cold reset (see
6.2.2), the maximum value shall be 5 MHz. For the maximum value supported by the card, see Table 7.
Unless otherwise specified, the duty cycle of the clock signal shall be between 40 % and 60 % of the cycle
during stable operation. When switching the frequency from one value to another, care should be taken to
ensure that no pulse is shorter than 40 % of the shortest cycle allowed by the card (see maximum frequency
in Table 7). No information shall be exchanged when switching the frequency value. Two different times are
recommended for switching the frequency value, either
⎯ after completion of an answer to reset, see 8.1, while the card is waiting for a character, or
⎯ after completion of a successful PPS exchange, see 9.3, while the card is waiting for a character.
© ISO/IEC 2006 – All rights reserved 7

Table 4 — Electrical characteristics of CLK under normal operating conditions
Symbol Conditions Minimum Maximum Unit
U 0,7 U U
IH CC CC V
I U –20 +100 µA
IH IH
U
IL Class A and class B 0 0,5 V
U Class C 0 0,2 U V
IL CC
I U –100 +20 µA
IL IL
t t C = 30 pF 9 % of cycle
R F IN
The voltage shall remain between – 0,3 V and U + 0,3 V.
CC
5.2.4 SPU (C6)
This contact is available for either standard or proprietary use, as input and/or output.
Depending upon whether the card uses SPU or not, the first TB for T=15 shall be present or absent in the
Answer-to-Reset: this global interface byte (see 8.3) indicates whether the use is standard or proprietary.
ISO/IEC JTC 1/SC 17 reserves the standard use for future use.
When the card is powered through VCC, if contact C6 is connected in the interface device, then the voltage
shall remain between – 0,3 V and U + 0,3 V.
CC
No card shall be damaged by an interface device where contact C6 is connected to VCC or GND as such an
interface device complies with the previous edition (ISO/IEC 7816-3:1997).
5.2.5 I/O (C7)
This contact is used as input (reception mode) or output (transmission mode). The information exchange uses
two states of the electrical circuit as follows:
⎯ state H if the card and the interface device are in reception mode or if the transmitter imposes this state;
⎯ state L if the transmitter imposes this state.
When both the card and the interface device are in reception mode, the electrical circuit shall be at state H.
When the card and the interface device are in non-matched transmission mode, the state may be indetermi-
nate. During operation, the interface device and the card shall not be simultaneously in transmission mode.
The interface device shall be able to support the defined range of input currents when the input voltages are
within the allowed range. The impedance presented by the interface device to the card shall allow the card to
keep the output voltages within the defined range.
Table 5 — Electrical characteristics of I/O under normal operating conditions
Symbol Conditions Minimum Maximum Unit
UIH 0,7 UCC UCC V
I U –300 +20 µA
IH IH
U 0 0,15 U V
IL CC
I U –1000 +20 µA
IL IL
U External pull-up resistor: 20 kΩ to U 0,7 U U V
OH CC CC CC
I U and external pull-up resistor: 20 kΩ to U +20 µA
OH OH CC
a a
U 0 0,15 U V
OL I = 1 mA for class A and class B CC
OL
a
I = 500 µA for class C
OL
t t C = 30 pF; C = 30 pF
R F IN OUT 1 µs
The voltage shall remain between – 0,3 V and U + 0,3 V.
CC
a
Interface device implementations should not require the card to sink more than 500 µA.
8 © ISO/IEC 2006 – All rights reserved

6 Card operating procedure
6.1 Principles
The electrical circuits shall remain not active until the contacts of the card are mechanically connected to the
contacts of the interface device. The interaction between the interface device and the card shall be conducted
through the following sequence of operations.
⎯ The interface device shall apply a class of operating conditions to the electrical circuits, i.e., activation,
cold reset and possibly one or more warm resets. If the card supports the class, it shall answer to reset
according to clause 8. The interface device ends up with a complete and valid Answer-to-Reset and a
class of operating conditions. The interface device shall be able to repeat the entire operation.
⎯ For exchanging information, the card and the interface device shall agree on a transmission protocol and
values of transmission parameters. Clause 10 specifies T=0, the half-duplex transmission of characters
with the interface device as the master. Clause 11 specifies T=1, the half-duplex transmission of blocks.
Clause 12 specifies the transmission of command-response pairs by T=0 and by T=1. When no
transmission is expected from the card (e.g., after processing a command-response pair and before
initiating the next one), the interface device may stop the clock signal if the card supports clock stop.
⎯ The interface device shall perform a deactivation.
The deactivation should be completed before the mechanical disconnection between the contacts of the card
and the contacts of the interface device.
6.2 Activation, resets and class selection
6.2.1 Activation
In order to initiate an interaction with a mechanically connected card, the interface device shall activate the
electrical circuits according to a class of operating conditions: A, B or C, see 5.1.3, in the following order.
⎯ RST shall be put to state L, see 5.2.2.
⎯ VCC shall be powered, see 5.2.1.
⎯ I/O in the interface device shall be put in reception mode, see 5.2.5. The interface device shall ignore the
state on I/O during activation.
⎯ CLK shall be provided with a clock signal, see 5.2.3.
NOTE 1 The delays between powering VCC, setting I/O in reception mode and providing the clock signal on CLK are not
defined.
NOTE 2 The interface device may perform a deactivation due to short circuits.
Figure 1 summarizes activation (before time T ) and cold reset (after time T ).
a a
H
VCC
L
H
CLK
L
H
t
RST b
L
t t
a c
H
I / O
Undefined L
L
Answer
T  T
a b
200 400 400 40 000
t ≤ ≤ t ≤ t ≤
a b c
f f f f
Figure 1 — Activation and cold reset
© ISO/IEC 2006 – All rights reserved 9

6.2.2 Cold reset
By the end of activation (RST in state L, VCC powered, I/O in reception mode in the interface device, CLK
provided with a suitable and stable clock signal), the card is ready for a cold reset. The internal state of the
card is not defined before a cold reset.
According to Figure 1, the clock signal is applied to CLK at time T . The card shall set I/O to state H within
a
200 clock cycles (delay t ) after the clock signal is applied to CLK (at time T + t ). The cold reset results from
a a a
maintaining RST at state L for at least 400 clock cycles (delay t ) after the clock signal is applied to CLK (at
b
time T + t ). The interface device shall ignore the state on I/O while RST is at state L.
a b
At time T , RST is put to state H. The answer on I/O shall begin between 400 and 40 000 clock cycles (delay
b
t ) after the rising edge of the signal on RST (at time T + t ). If the answer does not begin within 40 000 clock
c b c
cycles with RST at state H, the interface device shall perform a deactivation.
6.2.3 Warm reset
As the answer to a warm reset may differ from the answer to the previous reset, the interface device may
warm reset the card at any time, even during the answer to reset, but not before reception of the mandatory
characters TS and T0 (see 8.1). The warm reset shall not be initiated less than 4 464 (= 12 × 372) clock cycles
after the leading edge of character T0.
WARNING A warm reset initiated during the answer to reset may damage a card compliant with the previous edition
(ISO/IEC 7816-3:1997).
According to Figure 2, the interface device initiates a warm reset (at time T ) by putting RST to state L for at
c
least 400 clock cycles (delay t ) while VCC remains powered and CLK provided with a suitable and stable
e
clock signal. The card shall set I/O to state H within 200 clock cycles (delay t ) after state L is applied to RST
d
(at time T + t ). The interface device shall ignore the state on I/O while RST is at state L.
c d
At time T , RST is put to state H. The answer on I/O shall begin between 400 and 40 000 clock cycles (delay
d
t ) after the rising edge of the signal on RST (at time T + t ). If the answer does not begin within 40 000 clock
f d f
cycles with RST at state H, the interface device shall perform a deactivation.
H
t
RST e
L
t t
d f
H
I / O
Undefined L
L
Answer
T  T
c d
200 400 40 000
t ≤ ≤ t ≤ t ≤
d e f
f f f f
Figure 2 — Warm reset
6.2.4 Class selection
Figure 3 illustrates the principles of selection of the class of operating conditions. The figure is not exhaustive.
⎯ If the Answer-to-Reset carries a class indicator indicating the class being applied (see the first TA for
T=15 in 8.2), then normal operation may continue. Alternatively, the interface device may perform a
deactivation and after a delay of at least 10 ms, apply another class supported by the card.
⎯ If the Answer-to-Reset carries no class indicator, then the interface device shall maintain the current class.
If, after completion of the answer to reset, the card does not operate, then the interface device shall
perform a deactivation and after a delay of at least 10 ms, may apply another class.
⎯ If the card does not answer to reset, then the interface device shall perform a deactivation and either
• after a delay of at least 10 ms, apply another class, if any, or
• abort the selection process.
After abortion of a selection process, the interface device may initiate another selection process.
10 © ISO/IEC 2006 – All rights reserved

Start
Error handling Apply a class Delay
NO Select another
class
YES NO
Card answer
Answer is valid?
to reset?
YES
YES Take NO
Abort
further action?
Maintain
YES NO
Card indicates
Deactivate
current class?
class ?
NO YES
Continue normal
operation
Figure 3 — Class selection by the interface device
Once selected, the class shall not be changed during normal operation. For changing it, the interface device
shall perform a deactivation and after a delay of at least 10 ms, apply another class.
6.3 Information exchange
6.3.1 Selection of transmission parameters and protocol
After completion of the answer to reset, the card shall wait for characters from the interface device: their
transmission is governed by transmission parameters (see 7.1); their interpretation is governed by a protocol
(see 9, 10 and 11). Figure 4 illustrates the principles of selection of transmission parameters and protocol.
⎯ If TA (see 8.3) is present in the Answer-to-Reset (card in specific mode), then the interface device shall
start the specific transmission protocol using the specific values of the transmission parameters.
⎯ Otherwise (card in negotiable mode), for the transmission parameters, the values used during the answer
to reset (i.e., the default values of the transmission parameters, see 8.1) shall continue to apply as follows.
• If the value of the first character received by the card is 'FF', then the interface device shall have
started a PPS exchange (see 9); the default values of the transmission parameters shall continue to
apply until completion of a successful PPS exchange (see 9.3), after what the interface device shall
start the negotiated transmission protocol using the negotiated values of the transmission parameters.
• Otherwise, the interface device shall have started the “first offered transmission protocol” (see TD in
8.2.3). The interface device shall do so when the card offers only one transmission protocol and only
the default values of the transmission parameters. Such a card need not support PPS exchange.

Warm reset
Specific transmission protocol
Card in
(specific values)
specific mode
TA present
Negotiated transmission protocol
Answer to reset PPS exchange
(negotiated values)
(default values) (default values)
TA absent
Card in
First offered transmission protocol
negotiable mode
(default values)
Warm reset
Figure 4 — Selection of transmission parameters and protocol
© ISO/IEC 2006 – All rights reserved 11

NOTE 1 The value of PPSS ('FF', see 9.2) is invalid for CLA (T=0, see 10.3.2) and for NAD (T=1, see 11.3.2.1).
NOTE 2 In a multi-protocol card offering T=0 in negotiable mode, only T=0 can be “implicitly” selected.
NOTE 3 An interface device facing a card in negotiable mode and supporting neither PPS exchange nor the “first
offered transmission protocol” can perform either a warm reset or a deactivation.
NOTE 4 A card transmitting character TA to an interface device not aware of the existence of specific mode cannot rely
on a warm reset to switch the mode.
NOTE 5 An interface device having detected character TA should not initiate a warm reset before it detects either an
unsupported value in the received characters, or an overrun of WT (see 7.2).
6.3.2 Clock stop
For cards supporting clock stop, when the interface device expects no transmission from the card and when
I/O has remained at state H for at least 1 860 clock cycles (delay t ), then according to Figure 5, the interface
g
device may stop the clock on CLK (at time T ) while VCC remains powered and RST at state H.
e
H
CLK
Clock stop
L
t t
g h
H
I / O
L
L
Previous  Next
T  T
character e f character
1 860 700
≤ t ≤ t
g h
f f
Figure 5 — Clock stop
When the clock is stopped (from time T to time T), CLK shall be maintained either at state H or at state L
e f
according to the clock stop indicator X defined in 8.3.
At time T, the interface device restarts the clock and the information exchange on I/O may continue after at
f
least 700 clock cycles (at time T + t ).
f h
6.4 Deactivation
When information exchange is completed or aborted (e.g., unresponsive card, detection of card removal), the
interface device shall deactivate the electrical circuits in the following order (see Figure 6).
⎯ RST shall be put to state L.
⎯ CLK shall be put to state L (unless the clock is already stopped at state L).
⎯ I/O shall be put to state L.
⎯ VCC shall be deactivated.
H
VCC
L
H
CLK
L
H
RST
L
H
I / O
Undefined
L
Figure 6 — Deactivation
12 © ISO/IEC 2006 – All rights reserved

7 Asynchronous character
7.1 Elementary time unit
The nominal duration of one moment on the electrical circuit I/O is named “elementary time unit” and denoted
etu. The etu shall be equal to F / D clock cycles on the electrical circuit CLK where F and D are the
transmission parameters: F is the clock rate conversion integer and D the baud rate adjustment integer.
F 1
1 etu= ×
D f
The values of the transmission parameters shall be as specified in 6.3.1.
7.2 Character frame
According to Figure 7, a character consists of ten consecutive moments numbered 1 to 10. Each moment is
either at state H or at state L.
⎯ Before moment 1, the electrical circuit I/O shall be at state H.
⎯ Moment 1 shall be at state L. It is the character start.
⎯ Moments 2 to 9 shall encode a byte according to a coding convention (see TS in 8.1).
⎯ Moment 10 shall encode the character parity (see TS in 8.1).
⎯ After moment 10, both the card and the interface device shall remain in reception mode (in error-free
operation) for a certain time of “pause”, so that the electrical circuit I/O remains at state H.
Start Byte
Parity Start
H
1 2 3 4 5 6 7 8 9 10
Pause
L
Delay between consecutive characters

Figure 7 — Character frame
Figure 8 illustrates character timings: even with a maximum shift between the receiver time origin and the
transmitter time origin, the reception windows shall be all distinct from the transition windows.
0 1 2 3 4 5 6 7 8 9 10
Transmitter
etu
Distorted
(H) (H)
L
H H L H L L H L H
character
Parity
Start
Receiver
etu
0 0,5 1,5 2,5 3,5 4,5 5,5 6,5 7,5 8,5 9,5
first observation of state L Window for a transition on I/O
Window for a reception on I/O
last observation of state H
Figure 8 — Character timings
Within every character, if the state changes at the end of moment n for any n from 1 to 10, then the delay from
the character leading edge to the trailing edge of moment n shall be (n±0,2) etu.
When searching for a character, the receiver periodically samples the electrical circuit I/O. While the
transmitter time origin is the character leading edge, the receiver time origin is the mean between the last
observation of state H and the first observation of state L: the shift between time origins is at most half the
sampling time. The sampling time shall be less than 0,2 etu.
© ISO/IEC 2006 – All rights reserved 13

The receiver shall confirm the start moment before 0,7 etu (in receiver time). The receiver shall read the
second moment at (1,5±0,2) etu, the third moment at (2,5±0,2) etu, . the ninth moment at (8,5±0,2) etu and
the parity moment at (9,5±0,2) etu. Character parity is checked on the fly.
The minimum delay between the leading edges of two consecutive characters is named “guard time” and
denoted GT.
The maximum delay between the leading edge of a character transmitted by the card and th
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