EN 60958-3:2000

SLOVENSKI STANDARD
01-december-2000
Digitalni zvokovni vmesnik – 3. del: Uporaba pri potrošniku (IEC 60958-3:1999)
Digital audio interface -- Part 3: Consumer applications
Digitalton-Schnittstelle -- Teil 3: Allgemeingebrauch
Interface audionumérique -- Partie 3: Applications grand public
Ta slovenski standard je istoveten z: EN 60958-3:2000
ICS:
33.160.30 Avdio sistemi Audio systems
35.200 Vmesniška in povezovalna Interface and interconnection
oprema equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME CEI
INTERNATIONALE IEC
60958-3
INTERNATIONAL
Première édition
STANDARD
First edition
1999-12
Interface audionumérique –
Partie 3:
Applications grand public
Digital audio interface –
Part 3:
Consumer applications
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60958-3 © IEC:1999 – 3 –
CONTENTS
Page
FOREWORD . 7

Clause
1 Scope . 11

2 Normative references . 11

3 Interface format. 13

4 Channel status . 13
4.1 General. 13
4.2 Application . 13
4.2.1 Channel status general format. 13
4.2.2 Mode 0 channel status format for digital audio equipment for
consumer use . 19
4.3 Copyright management guidelines for consumer application of the digital
audio interface . 23
4.3.1 General. 23
4.3.2 Category code groups . 25
5 User data . 31
5.1 General. 31
5.2 Application . 31
5.2.1 User data message structure. 31
5.2.2 Equipment classification . 33
5.2.3 User data message length and contents . 35
6 Electrical and optical requirements . 39
6.1 General. 39
6.2 Timing accuracy. 39
6.2.1 Accuracy of sampling frequency (clock accuracy) . 39
6.2.2 Receiver locking range . 39
6.3 Unbalanced line . 39
6.3.1 General characteristics. 39
6.3.2 Line driver characteristics. 41
6.3.3 Line receiver characteristics . 43

6.3.4 Connectors . 45
6.4 Optical connection . 45
Annex A (normative) Application of the digital audio interface in the compact disc digital
audio system . 47
Annex B (normative) Application of the digital interface in the 2-channel pcm
encoder/decoder. 51
Annex C (normative) Application of the digital interface in the 2-channel digital audio
tape recorder in the consumer mode. 53
Annex D (normative) Application of the digital interface in laser optical digital audio
systems for which no other category code is defined . 61
Annex E (normative) Application of the digital interface in digital audio mixers in
the consumer mode . 63
Annex F (normative) Application of the digital interface in a sampling rate converter in
the consumer mode . 65

60958-3 © IEC:1999 – 5 –
Page
Annex G (normative) Application of the digital interface in digital sound samplers in

the consumer mode . 67

Annex H (normative) Application of the digital interface in 2-channel digital broadcast
receivers (Japan) in the consumer mode. 69

Annex J (normative) Application of the digital interface in 2-channel digital broadcast

receivers (Europe) in the consumer mode. 71

Annex K (normative) Application of the digital interface in 2-channel digital broadcast

receivers (USA) in the consumer mode . 73

Annex L (normative) Application of the digital interface in 2-channel electronic software
delivery in the consumer mode . 75
Annex M (normative) Application of the digital interface in the digital compact cassette
system in the consumer mode . 77
Annex N (normative) Application of the digital interface in the mini disc system in
the consumer mode . 87
Annex O (normative) Application of the digital interface in the digital sound processor in
the consumer mode . 89
Figure 1 – Example of message structure using information units. 33
Figure 2 – Simplified example of the configuration of the circuit (unbalanced). 41
Figure 3 – Rise and fall times . 41
Figure 4 – Intrinsic jitter measurement filter . 43
Figure 5 – Eye diagram. 45
Figure 6 – Receiver jitter tolerance template . 45
Figure C.1 – Example of different combinations of start-ID and shortening-ID. 59
Table 1 – Channel status general format for consumer use . 15
Table 2 – Mode 0 channel status format for consumer use . 19
Table 3 – Category code groups . 25
Table 4 – Category code groups for laser optical products . 27
Table 5 – Category code groups for digital/digital converter and signal processing products . 27
Table 6 – Category code groups for magnetic tape or magnetic disc based products . 27
Table 7 – Category code groups for broadcast reception of digitally encoded audio
with/without video signals . 29
Table 8 – Category code groups for musical instruments, microphones and other

sources that create original sound . 29
Table 9 – Category code groups for A/D converters for analogue signals without
copyright information . 29
Table 10 – Category code groups for A/D converters for analogue signals with
copyright information . 31
Table 11 – Category code groups for solid state memory based products . 31
Table A.1 – Example of 2-channel compact disc format . 49
Table C.1 – Use of Cp-bit, L-bit and category code for DAT. 55
Table C.2 – User data application in the DAT system . 57
Table M.1 – Deck status codes . 81

60958-3 © IEC:1999 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
DIGITAL AUDIO INTERFACE –
Part 3: Consumer applications
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard 60958-3 has been prepared by subcommittee 100C: Audio, video and
multimedia subsystems and equipment, of IEC technical committee 100: Audio, video and
multimedia systems and equipment.
The text of this standard is based on the following documents:
FDIS Report on voting
100C/248/FDIS 100C/254/RVD
Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
IEC 60958 consists of the following parts under the general title: Digital audio interface:
Part 1: General
Part 2 (TR): Software information delivery mode
Part 3: Consumer applications
Part 4: Professional applications
Annexes A to O form an integral part of this standard.

60958-3 © IEC:1999 – 9 –
The committee has decided that this publication remains valid until 2003.

At this date, in accordance with the committee’s decision, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or

• amended.
60958-3 © IEC:1999 – 11 –
DIGITAL AUDIO INTERFACE –
Part 3: Consumer applications
1 Scope
This International Standard describes an application of a serial, uni-directional, self-clocking

interface as defined in IEC 60958-1, for the interconnection of digital audio equipment for

consumer applications.
When used in a consumer digital processing environment, the interface is primarily intended to
carry stereophonic programmes, with a resolution of up to 20 bits per sample, an extension to
24 bits per sample being possible.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. For dated references, subsequent
amendments to, or revisions of, any of these publications do not apply. However, parties to
agreements based on this International Standard are encouraged to investigate the possibility
of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of IEC
and ISO maintain registers of currently valid International Standards.
IEC 60268-11:1987, Sound system equipment – Part 11: Application of connectors for the
interconnection of sound system components
IEC 60841:1988, Audio recording – PCM encoder/decoder system
IEC 60908:1999, Audio recording – Compact disc digital audio system
IEC 60958-1:1999, Digital audio interface – Part 1: General
IEC 60958-4:1999, Digital audio interface – Part 4: Professional applications
IEC 61119-1:1992, Digital audio tape cassette system (DAT) – Part 1: Dimensions and
characteristics
IEC 61119-6:1992, Digital audio tape cassette system (DAT) – Part 6: Serial copy management
system
60958-3 © IEC:1999 – 13 –
3 Interface format
The interface format as defined in IEC 60958-1 shall be used.

4 Channel status
4.1 General
For every sub-frame, the channel status provides information related to the audio channel that

is carried in that same sub-frame.
Channel status information is organized in a 192-bit block, subdivided into 24 bytes, numbered
0 to 23 (see table 1). The first bit of each block is carried in the frame with preamble “B”.
The individual bits of a block are numbered 0 to 191.
The primary application is indicated by channel status bit 0.
As stated in IEC 60958-1, for professional application this first channel status bit equals “1”.
For the consumer digital audio applications described in this standard, this first channel status
bit equals “0”.
Secondary applications may be defined within the framework of these primary applications.
4.2 Application
4.2.1 Channel status general format
For each channel, channel status is used for the following information.

60958-3 © IEC:1999 – 15 –
Table 1 – Channel status general format for consumer use

Byte
0 a = “0” b c d Mode
bit 0 12 34 5 6 7
bit 8 9 1011 121314 15
bit 1617 1819 202122 23
bit 2425 2627 282930 31
bit 3233 3435 363738 39
bit 4041 4243 444546 47
bit 4849 5051 525354 55
bit 5657 5859 606162 63
bit 6465 6667 686970 71
bit 7273 7475 767778 79
bit 8081 8283 848586 87
bit 8889 9091 929394 95
bit 96 97 98 99 100 101 102 103
bit 104 105 106 107 108 109 110 111
bit 112 113 114 115 116 117 118 119
bit 120 121 122 123 124 125 126 127
bit 128 129 130 131 132 133 134 135
bit 136 137 138 139 140 141 142 143
bit 144 145 146 147 148 149 150 151
bit 152 153 154 155 156 157 158 159
bit 160 161 162 163 164 165 166 167
bit 168 169 170 171 172 173 174 175
bit 176 177 178 179 180 181 182 183
bit 184 185 186 187 188 189 190 191
a: use of channel status block. c: copyright information.
b: linear PCM identification. d: additional format information.

60958-3 © IEC:1999 – 17 –
Byte 0: General control and mode information

Control:
Bit 0 “0” Consumer use of channel status block.

NOTE The significance of byte 0, bit 0 is such that transmission from an interface conforming to IEC 60958-4 can
be identified.
Bit 1 “0” Audio sample word represents linear PCM samples.

“1” Audio sample word used for other purposes.
Bit 2 “0” Software for which copyright is asserted.
“1” Software for which no copyright is asserted.
NOTE Bit 2 is referred to as the “Cp-bit”. It should be indicated whether copyright protection has been asserted.
The copyright status may be unknown for certain applications. The above interpretation is
therefore not valid in combination with some category codes (see annexes). The Cp-bit can
alternate between 0 and 1 at a rate between 4 Hz and 10 Hz (see annex A).
Bits Additional format information, meaning depends on bit 1.
3-5
When bit 1 = “0”, linear PCM audio mode:
bit 3 4 5
state “0 0 0” 2 audio channels without pre-emphasis.
“1 0 0” 2 audio channels with 50/15 μs pre-emphasis.
“0 1 0” Reserved (for 2 audio channels with pre-emphasis).
“1 1 0” Reserved (for 2 audio channels with pre-emphasis).
All other states of bits 3-5 are reserved and shall not be used until further
defined.
When bit 1 = “1”, other than linear PCM applications:
bit 3 4 5
state “0 0 0” Default state for applications other than linear PCM.

All other states of bits 3-5 are reserved and shall not be used until further
defined.
Bits Channel status mode, indicates one of four possible channel status formats
6-7 (bytes 1 to 23). There are four possible modes for each of the states of bit 1.
bit 6 7
state “0 0” Mode 0, refer to 4.2.2.
All other states of bits 6-7 are reserved and shall not be used until further
defined.
The contents of bits 8 to 191 depend on the mode as indicated by bits 6 and 7. If not defined
otherwise, the default value is “0”.

60958-3 © IEC:1999 – 19 –
4.2.2 Mode 0 channel status format for digital audio equipment for consumer use

When the audio sample word represents linear PCM and the channel status mode is mode 0,

the following channel status format should be applied:

Table 2 – Mode 0 channel status format for consumer use

Byte
0 a = “0” b = “0” c d Mode = “0 0”

bit 0 1 2 34567
1 Category code
bit 8 9 10 1112 1314 15
2 Source number Channel number
bit 1617 1819 20 21 22 23
3 Sampling frequency Clock accuracy
bit 2425 2627 28 29 30 31
4 Word length
bit 3233 3435 36 37 38 39
bit 4041 4243 44 45 46 47
bit 4849 5051 52 53 54 55
bit 5657 5859 60 61 62 63
bit 6465 6667 68 69 70 71
bit 7273 7475 76 77 78 79
bit 8081 8283 84 85 86 87
bit 8889 9091 92 93 94 95
bit 96 97 98 99 100 101 102 103
bit 104 105 106 107 108 109 110 111
bit 112 113 114 115 116 117 118 119
bit 120 121 122 123 124 125 126 127
bit 128 129 130 131 132 133 134 135
bit 136 137 138 139 140 141 142 143
bit 144 145 146 147 148 149 150 151
bit 152 153 154 155 156 157 158 159
bit 160 161 162 163 164 165 166 167
bit 168 169 170 171 172 173 174 175
bit 176 177 178 179 180 181 182 183
bit 184 185 186 187 188 189 190 191
a: use of channel status block. c: copyright information.
b: linear PCM identification. d: additional format information.

60958-3 © IEC:1999 – 21 –
Byte 0 as defined in 4.2.1, with:

Bit 1 “0” Audio sample word represents linear PCM samples.

Bits 6-7 “0 0” Mode 0.
Byte 1: Category code
The category code indicates the kind of equipment that generates the digital audio interface

signal. See the relevant annexes for the assignments. Bit 8 = LSB, bit 15 = MSB.

Byte 2: Source and channel number
Bits 16-19 Source number, bit 16 = LSB, bit 19 = MSB.
bit 16 17 18 19
state “0 0 0 0” Do not take into account.
“1 0 0 0” 1
“0 1 0 0” 2
“1 1 0 0” 3
............
“1 1 1 1” 15
Bits 20-23 Channel number (audio channel), bit 20 = LSB, bit 23 = MSB.
bit 20 21 22 23
state “0 0 0 0” Do not take into account.
“1 0 0 0” A (left channel for stereo channel format).
“0 1 0 0” B (right channel for stereo channel format).
“1 1 0 0” C
................
“1 1 1 1” O
Byte 3: Sampling frequency and clock accuracy
Bits 24-27 Sampling frequency
bit 24 25 26 27
state “0 0 0 0” 44,1 kHz
“0 1 0 0” 48 kHz
“1 1 0 0” 32 kHz
All other combinations are reserved and shall not be used until further
defined.
Bits 28-29 Clock accuracy.
bit 28 29
state “0 0” Level II.
“1 0” Level I.
“0 1” Level III.
“1 1” Reserved.
60958-3 © IEC:1999 – 23 –
Byte 4: Word length
Bit 32 “0” Maximum audio sample word length is 20 bits.

“1” Maximum audio sample word length is 24 bits.

Bits 33- Sample word length
bit 33 34 35 Audio sample word Audio sample word length

length if maximum length if maximum length is 20

is 24 bits as indicated by bits as indicated by bit 32.
bit 32.
state “0 0 0” Word length not indicated Word length not indicated
(default) (default)
“1 0 0” 20 bits 16 bits
“0 1 0” 22 bits 18 bits
“0 0 1” 23 bits 19 bits
“1 0 1” 24 bits 20 bits
“0 1 1” 21 bits 17 bits
All other combinations are reserved and shall not be used until further
defined.
NOTE The first edition of IEC 60958 had bits 32 to 35 reserved and set to zero. Therefore, the all zero state for
these bits on a received signal may be an indicator that the word length indication has not been implemented.
Unless otherwise specified in the annexes, the following specification is applicable:
• Audio sample word has a length of 20 bits/sample. The auxiliary sample bits are an optional
expansion of the audio sample, if not used = “0”.
• User data is not used, all bits = “0”.
• Channel status is identical for all channels, with the exception of the channel number, if not
equal to zero.
4.3 Copyright management guidelines for consumer application of the digital
audio interface
4.3.1 General
Category codes are defined for all consumer products that are capable of supplying a digital

signal to consumer digital audio recorders, except for products that are fully transparent from
input to output.
Category codes for products have been grouped by general function of the product. This
makes it possible to take into account future digital recording products not yet defined in detail.
Such a product then deals with the group code under a general rule. These rules define
whether a digital recorder is enabled to record a copyright protected digital signal.
Unless otherwise specified, any consumer equipment capable of transferring digital audio
information from an input terminal to an output terminal, if not fully transparent and regardless
of the delay or kind of transformation of the audio content of the signal, shall copy channel
status bits 0, 1, 3, 4, 5, 6 and 7 from the source. Bit 2 shall be copied from the source, unless
otherwise specified in the annexes.
Bit 15 is referred to as the “L-bit”. It shall indicate the “generation status” of the digital audio
signal.
60958-3 © IEC:1999 – 25 –
“Generation status” means:
• whether the signal emanates from a source that has been produced or published or

authorized by the rights owner of the material, such as commercially released pre-recorded
compact discs or DAT tapes or a digital broadcast (referred to herein as “original”) and for
which copyright has been asserted;

• or whether the signal emanates from a recording made from such “original” material

(referred to herein as “a home-copy of generation 1 or higher”).

Generally the L-bit is specified as:

Bit 15 “0” No indication.
“1” Commercially released pre-recorded software.
For historical reasons, the reverse situation is valid for the signals originating from:
laser optical products (category code “100 XXXXL”);
broadcast reception (category codes “001 XXXXL” and “011 1XXXL”).
For these category codes the L-bit shall indicate:
Bit 15 “0” Commercially released pre-recorded software.
“1” No indication.
The generation status may be unknown for certain applications. The above interpretation is
therefore not valid in combination with some category codes such as:
• general (category code “000 00000”);
• analogue/digital converters for analogue signals without copyright information (category
code “011 00XXL”).
4.3.2 Category code groups
4.3.2.1 The category code groups are defined in table 3.
Table 3 – Category code groups
Bit 8. 15 Category
“000 00000” General. Used temporarily
“100 XXXXL” Laser optical products
“010 XXXXL” Digital/digital converters and signal processing products

“110 XXXXL” Magnetic tape or disc based products
“001 XXXXL” Broadcast reception of digitally encoded audio signals with or without video signals
and
“011 1XXXL”
“101 XXXXL” Musical instruments, microphones and other sources without copyright information
“011 00XXL” Analogue/digital converters for analogue signals without copyright information
“011 01XXL” Analogue/digital converters for analogue signals which include copyright information
in the form of “Cp-bit and L-bit status”
“000 1XXXL” Solid state memory based products
“000 0001L” Experimental products not for commercial sale
“111 XXXXL” Not defined. Reserved
“000 0XXXL” Not defined. Reserved, except “000 00000” and “000 0001L”

60958-3 © IEC:1999 – 27 –
4.3.2.2 Within a group a further indication of the kind of source is given.

4.3.2.2.1 For the general category code (“000 00000”) the following applies:

– used temporarily;
– applied specifically for digital audio broadcast reception with or without a video signal, for

example digital satellite reception in Japan in the case where no copyright information is

transmitted. (See also annex H.)

4.3.2.2.2 For the group of laser optical products (category code = “100 XXXXL”) the category

codes are defined in table 4.
Table 4 – Category code groups for laser optical products
Bit 8. 15 Category
“100 00000” Compact disc digital audio signal compatible with IEC 60908 (see annex A)
“100 1000L” Laser optical digital audio systems for which no other category code is defined (see
annex D)
“100 1001L” Mini disc system (see annex N)
“100 1100L” Digital versatile disc (DVD)
“100 others” Reserved
4.3.2.2.3  For the group of digital/digital converters and signal processing products (category
code = “010 XXXXL”), the category codes are defined in table 5.
Table 5 – Category code groups for digital/digital converter and signal processing products
Bit 8. 15 Category
“010 0000L” PCM encoder/decoder (see annex B)
“010 0100L” Digital signal mixer (see annex E)
“010 1100L” Sampling rate converter (see annex F)
“010 0010L” Digital sound sampler (see annex G)
“010 1010L” Digital sound processor (see annex O)
“010 others” Reserved
4.3.2.2.4 For the group of magnetic tape or magnetic disc based products (category code =

“110 XXXXL”), the category codes are defined in table 6.
Table 6 – Category code groups for magnetic tape or magnetic disc based products
Bit 8. 15 Category
“110 0000L” DAT (see annex C)
“110 1000L” Video tape recorder with digital sound
“110 0001L” Digital compact cassette (see annex M)
“110 others” Reserved
60958-3 © IEC:1999 – 29 –
4.3.2.2.5 For the group of broadcast reception of digitally encoded audio with/without video

signals (category code = “001 XXXXL” or “011 1XXXL”), the category codes are defined in

table 7.
Table 7 – Category code groups for broadcast reception of digitally encoded audio

with/without video signals
Bit 8. 15 Category
“001 0000L” Digital audio broadcast signal with or without a video signal (Japan) (see annex H)

“001 1000L” Digital audio broadcast signal with or without a video signal (Europe) (see annex J)

“001 0011L” Digital audio broadcast signal with or without a video signal (USA) (see annex K)
“001 0001L” Electronic software delivery (see annex L)
“001 others” Reserved
“011 1XXXL” Reserved
4.3.2.2.6 For the group of musical instruments, microphones and other sources that create
original sound (category code = “101 XXXXL”), the category codes are defined in table 8.
Table 8 – Category code groups for musical instruments, microphones and
other sources that create original sound
Bit 8. 15 Category
“101 0000L” Synthesizer
“101 1000L” Microphone
“101 others” Reserved
4.3.2.2.7 For the group of analogue/digital converters for analogue signals without copyright
information (category code = “011 00XXL”), the category codes are defined in table 9.
Table 9 – Category code groups for A/D converters for analogue signals
without copyright information
Bit 8. 15 Category
“011 0000L” A/D converter
“011 00 others” Reserved
4.3.2.2.8 For the group of analogue/digital converters for analogue signals which include
copyright information in the form of “Cp-bit and L-bit status” (category code = “011 01XXL”), the
category codes are defined in table 10.

60958-3 © IEC:1999 – 31 –
Table 10 – Category code groups for A/D converters for analogue signals

with copyright information
Bit 8. 15 Category
“011 0100L” A/D converter
“011 01 others Reserved
4.3.2.2.9 For the group of solid state memory based products (category code = “000 1XXXL”),
the category codes are defined in table 11.

Table 11 – Category code groups for solid state memory based products
Bit 8. 15 Category
“000 1XXXL” Reserved
4.3.2.2.10 For experimental products not for commercial sale (category code = “000 0001L”),
the following definition applies.
New products for which a category code is not yet defined, or for which circuitry to signal the
appropriate category code is not yet available.
5 User data
5.1 General
The default value of the user bits is logical “0”.
For interchangeability of equipment it is strongly recommended to use the format described
below for consumer applications of the user data.
5.2 Application
All the user data bits from all sub-frames are considered to form a single bit stream.
5.2.1 User data message structure
A message consists of information units (IUs). An IU consists of one start bit (logical value “1”)

followed by 7 information bits.
The 8 bits of an IU are also referred to as the P, Q, R, S, T, U, V and W bits. IUs in a message
are separated by up to and including 8 bits with a logical value “0”. The nominal number of bits
with logical value “0” between IUs is 4. Messages are separated by more than 8 bits with a
logical value “0”.
60958-3 © IEC:1999 – 33 –
Bit 012 345678 910 11
0 001 Q R S T U V W 00A)
+12 001 Q R S T U V W 0 0
+24 1 Q R S T U V W 0 000B)
+36 000 01Q R S T U V W C)
+48 1 Q R S T U V W 0 000
+60 1 Q R S T U V W 0 000D)
+72 000 00001Q R S T
+84 U V W 00001Q R S T E)
+96 U V W 000001 Q R S
Key
0 Bit between IUs with logical value “0”
1 Start bit P, first bit of IU with logical value “1”
Q, R, S, T, U, V, W Information bits
A) Example of an IU: start bit plus 7 information bits
B) Maximum distance between 2 IUs of the same message is 8 bits
C) Minimum distance between 2 IUs of the same message is 0 bits
D) Distance of more than 8 bits between IUs indicates start of a new message
IEC  1743/99
E) Nominal distance between 2 IUs of the same message is 4 bits
Figure 1 – Example of message structure using information units
5.2.2 Equipment classification
Equipment is divided into three classes, according to the category code of the channel status.
See also the relevant annexes.
Future equipment, for which there is no relevant annex, shall be classified as belonging to one
of the three classes defined below.
5.2.2.1 Class I: original user data generating equipment
Original user data generating equipment will generate user data bits according to a format that
is defined in the standard for that equipment. See the relevant annex.

Any new equipment in this class will carry the general user data format as defined hereinafter.
5.2.2.2 Class II: user data transparent equipment
The user data transparent equipment shall either provide all “0” user data bits, or transfer the
user data bits it receives from its input unchanged to its output. If the processing of the audio
information causes considerable delay, it is recommended that the user data bits should be
equally delayed.
5.2.2.3 Class III: mixed mode user data equipment
As with the user data transparent equipment, this class of products will mainly transfer the user
data bits from its input to its output. However, in some specific cases deviation from this rule is
allowed.
60958-3 © IEC:1999 – 35 –
The possible user data formats for this class are:

• all “0” bits;
• the complete user data information of the input, or one of the inputs in the case of multiple

inputs;
• the general user data format. The information carried in this case may originate from within

the equipment itself, or be transcoded from the input source(s).

5.2.3 User data message length and contents

The possible length and contents of the user data messages depends on the category code of
the equipment. See the relevant annexes.
For new equipment that is capable of generating original user data contents, the general user
data format shall be used.
5.2.3.1 General user data format
According to the general user data format a message consists of a minimum of 3 and a
maximum of 129 information units, except for a length of 96 information units. A total message
length of 96 information units is reserved for some specific laser optical products (see 5.2.3.2).
The contents of the first IU are shown below:
1 (Start) 1 (Q) Mode R Mode S Mode T Item U Item V Item W
The bits R, S, T, U, V, W have the following meaning:
Mode RST
000 Not used, reserved for digital compact cassette (DCC).

1XX


X1X May be used for new messages.

XX1

The mode bits indicate a class of messages, for example text, preset information, etc., and the
item bits give a further definition of the type of message.
It is recommended that any new application should conform as much as possible to messages

coded according to the general user data format that have been defined for other applications.
The second IU contains a number indicating the following number of IUs:
1 (Start) IU IU IU IU IU IU IU
Count 6 Count 5 Count 4 Count 3 Count 2 Count 1 Count 0
IU count 6 is the most significant bit, IU count 0 is the least significant bit. The number is coded
as a binary number in the range 1 to 127 (000 0001b to 111 1111b), except 94.

60958-3 © IEC:1999 – 37 –
The third IU contains the originating category code, without the L-bit, of the equipment that

generates the general user data format messages:

1 C-Ch C-Ch C-Ch C-Ch C-Ch C-Ch C-Ch
(Start) bit 8 bit 9 bit 10 bit 11 bit 12 bit 13 bit 14

The L-bit (C-channel bit 15) is not carried in this message, as it is not relevant for the decoding

of the user data messages. Therefore, any decisions on the copyright status of the audio

information shall be based on the category code and Cp bit as carried in the channel status.

The IUs that follow contain user information.
User information that originally was organized as bytes is carried as follows: four successive
IUs carry a maximum of three successive bytes (X, Y and Z, 7 = MSB, 0 = LSB) in bits R, S, T,
U, V, W of the IUs:
1 (Start) Q X7 X6 X5 X4 X3 X2
1 (Start) Q X1 X0 Y7 Y6 Y5 Y4
1 (Start) Q Y3 Y2 Y1 Y0 Z7 Z6
1 (Start) Q Z5 Z4 Z3 Z2 Z1 Z0
The Q bits can optionally indicate that the remaining six bits of the IU contain an error:
“0” no error detected.
“1” error in bits R, S, T, U, V, W.
If not used, the error flag should be set to a logical “0” value.
If the number of bytes to transfer does not fill a complete quadruplet (i.e. just 1 or 2 bytes,
not 3 bytes), the remaining byte(s) shall be coded “0 0 0 0 0 0 0 0”.
5.2.3.2 General user data format for some specific laser optical products
For historical reasons the laser optical products with category codes “100 0000” (compact disc
digital audio, see IEC 60908) and “100 1001L” (mini disc) employ a user data format that
differs from the one defined above. In this format no message length specifier is applied.
Instead the length is fixed to 96 IUs. The information in the Q bits of the IUs is considered to be
in a separate channel (the Q channel).

Each group of six bits R, S, T, U, V, W of an information unit is called a SYMBOL.
The SYMBOL numbering follows the numbering of the bits in table A.1.
A group of 24 SYMBOLS is called a PACK:
PACK 1 is formed by symbols 1 to 24;
PACK 2 is formed by symbols 25 to 48;
PACK 3 is formed by symbols 49 to 72;
PACK 4 is formed by symbols 73 to 96.
Information will be carried in the PACKS according to specific formats.

60958-3 © IEC:1999 – 39 –
6 Electrical and optical requirements

6.1 General
Two types of transmission lines are defined: unbalanced and optical fibre.

6.2 Timing accuracy
6.2.1 Accuracy of sampling frequency (clock accuracy)

Three levels of sampling frequency accuracy are defined to meet various requirements of the
frequency accuracy. These levels shall be indicated in the channel status data.
6.2.1.1 Level I: high accuracy mode
–6
Tolerance of transmitting sampling frequency shall be within ±50 × 10 .
6.2.1.2 Level II: normal accuracy mode
–6
Tolerance of transmitting sampling frequency shall be within ±1 000 × 10 .
6.2.1.3 Level III: variable pitch shifted clock mode
The signal in this mode can be received by specially designed receivers.
NOTE The frequency range is under consideration. A value of ±12,5 % is envisaged.
6.2.2 Receiver locking range
By default, receivers should be able to lock to signals of level II accuracy with respect to the
three standard sampling frequencies.
If a receiver is only capable of normal operation with a narrower locking range, then this range
should exceed the sample frequency tolerance of level I and it shall be specified as a level I
receiver.
If a receiver is capable of normal operation at sample rate variations corresponding to level III,
then this shall be specified as a level III receiver.
6.3 Unbalanced line
6.3.1 General characteristics
The interconnecting cable shall be unbalanced and screened (shielded) with a nominal
characteristic impedance of 75 Ω ± 35 % at frequencies from 0,1 MHz to 6,0 MHz.

60958-3 © IEC:1999 – 41 –
The transmission circuit configuration shown in figure 2 may be used.

Transmitter Interconnecting cable Receiver

IEC  1744/99
Figure 2 – Simplified example of the configuration of the circuit (unbalanced)
NOTE For implementation additional components may be needed. A transformer in the transmitter with a floating
(non-earthed) secondary can be used to avoid any potential earth loops and provide a useful bandwidth limitation to
reduce high-frequency radiation.
6.3.2 Line driver characteristics
6.3.2.1 Output impedance
The line driver shall have an unbalanced output with an internal impedance of (75 ± 20 %) Ω,
when measured at the terminals to which the line is connected, at frequencies from 0,1 MHz
to 6 MHz.
6.3.2.2 Signal amplitude
The signal amplitude shall be 0,5 V ± 20 % peak-to-peak, when measured across a (75 ± 1 %) Ω
resistor connected to the output terminals, without any interconnecting cable present.
6.3.2.3 DC output voltage
The d.c. voltage shall be less than 0,05 V, when measured across a (75 ± 1 %) Ω resistor
connected to the output terminals, without any interconnecting cable present.
6.3.2.4 Rise and fall times
The time difference between the 10 % and 90 % points of any transition shall be less than

0,4 UI (see figure 3).
1,0 UI 1,0 UI
90 %
50 %
10 %
< 0,4 UI < 0,4 UI
IEC  1745/99
Figure 3 – Rise and fall times

60958-3 © IEC:1999 – 43 –
6.3.2.5 Intrinsic jitter
The peak intrinsic output jitter measured at all the data transition zero crossings shall be less

than 0,05 UI when measured with the intrinsic jitter measurement filter.

NOTE This applies both when the equipment is locked to an effectively jitter-free timing reference (which may be a

modulated digital audio signal) and when the equipment is free-running.

The jitter weighting filter is shown in figure
...