ISO 21806-1:2020

INTERNATIONAL ISO
STANDARD 21806-1
First edition
2020-09
Road vehicles — Media Oriented
Systems Transport (MOST) —
Part 1:
General information and definitions
Véhicules routiers — Système de transport axé sur les médias —
Partie 1: Information générale et définitions
Reference number
ISO 21806-1:2020(E)
©
ISO 2020

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ISO 21806-1:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
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ISO 21806-1:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 9
4.1 Symbols . 9
4.2 Abbreviated terms . 9
5 Access to MOST specification versions .10
5.1 General .10
5.2 ISO standards maintenance portal .11
5.3 MOST versions directory structure .11
Annex A (normative) List of implementation relevant documents .13
Annex B (informative) List of supplemental documents .21
Bibliography .23
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ISO 21806-1:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 31,
Data communication.
A list of all parts in the ISO 21806 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 21806-1:2020(E)

Introduction
The Media Oriented Systems Transport (MOST) communication technology was initially developed at
the end of the 1990s in order to support complex audio applications in cars. The MOST Cooperation was
founded in 1998 with the goal to develop and enable the technology for the automotive industry. Today,
1)
MOST enables the transport of high quality of service (QoS) audio and video together with packet data
and real-time control to support modern automotive multimedia and similar applications. MOST is a
function-oriented communication technology to network a variety of multimedia devices comprising
one or more MOST nodes.
Figure 1 shows a MOST network example.
Figure 1 — MOST network example
The MOST communication technology provides:
— synchronous and isochronous streaming,
— small overhead for administrative communication control,
— a functional and hierarchical system model,
— API standardization through a function block (FBlock) framework,
— free partitioning of functionality to real devices,
— service discovery and notification, and
[2]
— flexibly scalable automotive-ready Ethernet communication according to ISO/IEC/IEEE 8802-3 .
MOST is a synchronous time-division-multiplexing (TDM) network that transports different data types
on separate channels at low latency. MOST supports different bit rates and physical layers. The network
clock is provided with a continuous data signal.
®
1) MOST is the registered trademark of Microchip Technology Inc. This information is given for the convenience
of users of this document and does not constitute an endorsement by ISO.
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ISO 21806-1:2020(E)

Within the synchronous base data signal, the content of multiple streaming connections and control
data is transported. For streaming data connections, bandwidth is reserved to avoid interruptions,
collisions, or delays in the transport of the data stream.
MOST specifies mechanisms for sending anisochronous, packet-based data in addition to control data
and streaming data. The transmission of packet-based data is separated from the transmission of
control data and streaming data. None of them interfere with each other.
A MOST network consists of devices that are connected to one common control channel and packet
channel.
In summary, MOST is a network that has mechanisms to transport the various signals and data streams
that occur in multimedia and infotainment systems.
The ISO standards maintenance portal (https:// standards .iso .org/ iso/ ) provides references to MOST
specifications implemented in today's road vehicles because easy access via hyperlinks to these
specifications is necessary. It references documents that are normative or informative for the MOST
versions 4V0, 3V1, 3V0, and 2V5.
The ISO 21806 series has been established in order to specify requirements and recommendations
for implementing the MOST communication technology into multimedia devices and to provide
conformance test plans for implementing related test tools and test procedures.
To achieve this, the ISO 21806 series is based on the open systems interconnection (OSI) basic reference
[1] [3]
model in accordance with ISO/IEC 7498-1 and ISO/IEC 10731 , which structures communication
systems into seven layers as shown in Figure 2. Stream transmission applications use a direct stream
data interface (transparent) to the data link layer.
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ISO 21806-1:2020(E)

Figure 2 — The ISO 21806 series reference according to the OSI model
The International Organization for Standardization (ISO) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent.
ISO takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In
this respect, the statement of the holder of this patent right is registered with ISO. Information may be
obtained from the patent database available at www .iso .org/ patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those in the patent database. ISO shall not be held responsible for identifying
any or all such patent rights.
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INTERNATIONAL STANDARD ISO 21806-1:2020(E)
Road vehicles — Media Oriented Systems Transport
(MOST) —
Part 1:
General information and definitions
1 Scope
This document provides general information and definitions for Media Oriented Systems Transport
(MOST), a synchronous time-division-multiplexing network.
This document describes the access to MOST specifications, which are referenced by the ISO 21806 series.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
2)
MOST Specification Rev. 2.5.0, 10/2006
3)
MOST Specification Rev. 3.0.0E2, 07/2010
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
accumulated jitter
portion of jitter (3.31) at any point in a MOST network (3.43) that is made up entirely of the transferred
jitter (3.84) from all previous nodes (3.57)
3.2
accumulated phase variation
portion of phase variation (3.61) at any point in a MOST network (3.43) that is made up entirely of the
transferred jitter (3.84) and transferred wander (3.85) from all previous nodes (3.57)
3.3
alignment jitter
AJ
jitter (3.31) that affects the reception of data by degrading the receiver eye with horizontal closure
2) See Annex A.
3) See Annex A.
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3.4
anisochronous
DEPRECATED: asynchronous
qualifying a time-varying phenomenon, a timescale or a signal the consecutive significant instants of
which are separated by time intervals which are not all constrained to have the same rated duration or
to have rated durations equal to integral multiples of a unit duration
[SOURCE: IEC Electropedia, 702-04-15, modified — Note 1 to entry was deleted.]
3.5
average pulse width distortion
APWD
average deviation of the signal pulses from their ideal width
3.6
bit rate
BR
number of binary digits transferred per second
[SOURCE: IEC Electropedia, 704-16-07, modified — The term "binary digit rate" was deleted.]
3.7
bits per frame
BPF
number of bits in a network frame (3.54)
3.8
boundary descriptor
value that determines the amount of bandwidth allocated for streaming data (3.75) and packet data (3.60)
3.9
bypass
mechanism that forwards data from Rx to Tx, performing data recovery and clock recovery
3.10
channel
means of transmission of signals in one direction between two points
[SOURCE: IEC Electropedia, 701-02-01, modified — The term was originally "transmission channel"
and Notes 1 and 2 to entry were deleted.]
3.11
channel frame
frame (3.26) that is transported on a channel (3.10)
3.12
connection label
CL
identifier for a streaming connection (3.74)
3.13
control channel
channel (3.10) that is used to transport control data (3.14)
3.14
control data
small data packets with low latency
3.15
control frame
frame (3.26) that transports control data (3.14)
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3.16
critical unlock
CU
unlock (3.88) or series of unlocks that exceed a certain time
3.17
data-dependent jitter
DDJ
jitter (3.31) generated by changes in the transmitted data pattern
3.18
duplex
pertaining to a mode of operation in which information can be transmitted in both directions
simultaneously between two points
[SOURCE: IEC Electropedia, 701-03-171, modified — The deprecated term "full duplex" was deleted.]
3.19
electrical wake-up line
external line that initiates a network wake-up event
3.20
electromagnetic compatibility
EMC
ability of equipment or a system to function satisfactorily in its electromagnetic environment without
introducing intolerable electromagnetic disturbances to anything in that environment
[SOURCE: IEC Electropedia, 161-01-07]
3.21
electromagnetic interference
EMI
degradation of the performance of an equipment, transmission channel (3.10) or system caused by an
electromagnetic disturbance
[SOURCE: IEC Electropedia, 161-01-06, modified — Notes 1 and 2 to entry were deleted.]
3.22
electronic control unit
ECU
unit adjustable by other than mechanical means (e.g. sensing unit), containing electronic components
and controlling the output via electronic components
[SOURCE: IEC Electropedia, 442-04-22]
3.23
established MOST specification
documents that comply with MOST version 3V0, or 2V5
3.24
eye diagram
“eye-shaped” oscilloscope pattern obtained from the superposition of the signal waveforms from
successive time intervals each allocated to one digit
Note 1 to entry: The eye diagram is used to indicate the amplitude and time margins available to decode the
digital signal.
[SOURCE: IEC Electropedia, 723-10-75, modified — The term "eye pattern" was deleted and "the" was
removed from the beginning of the definition.]
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3.25
fall time
time interval between the instants at which the instantaneous value of a pulse again reaches a specified
upper value and then a specified lower value
Note 1 to entry: Unless otherwise specified, the upper and lower values are fixed at 90 % and 10 % of the pulse
magnitude.
[SOURCE: IEC Electropedia, 702-03-06, modified — The term "decay time" was deleted.]
3.26
frame
repetitive set of consecutive time-slots constituting a complete cycle of a signal or of another process in
which the relative position of each time-slot in the cycle can be identified
[SOURCE: Electropedia, 704-14-01, modified — Notes 1 and 2 to entry were deleted.]
3.27
frequency reference
device, usually crystal controlled, that provides an accurate and low drift frequency standard for the
MOST network controller (3.44) and MOST network (3.43) timing
3.28
Golden PLL
hardware or software entity that is used to recover the clock required to form an eye diagram (3.24)
3.29
isochronous
qualifying a time-varying phenomenon, a timescale, or a signal the consecutive significant instants of
which are separated by time intervals that all have the same rated duration or have rated durations
equal to integral multiples of a unit duration
[SOURCE: IEC Electropedia, 702-04-13, modified — The deprecated term "synchronous" was deleted
and the Note 1 to entry was deleted.]
3.30
isochronous channel
channel (3.10) that is used to transport isochronous (3.29) data on the network frame (3.54)
3.31
jitter
set of short-term non-cumulative variations in the significant instants of a digital signal from their ideal
positions in time
[SOURCE: IEC Electropedia, 704-16-13, modified — Notes 1 and 2 to entry were deleted.]
3.32
link
signal path between a sending MOST network controller (3.44) and a receiving MOST network controller
3.33
listen-only node
node (3.57) that does not change the content of network frames (3.54)
3.34
lock
reception of three consecutive PREAMBLEs that are aligned to the bit stream and occur at the correct
bit location in the network frame (3.54)
3.35
lock flag
flag that the TimingMaster (3.81) sets when it reaches stable lock (3.34)
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3.36
logical node address
address value for point-to-point transfers between nodes (3.57) that may be assigned independent of
the node position
3.37
low-level retry
retransmission of the channel frame (3.11) after a certain waiting period
3.38
MOST50
MOST network (3.43) with a bit rate (3.6) of 50 Mbit/s
3.39
MOST150
MOST network (3.43) with a bit rate (3.6) of 150 Mbit/s
3.40
MOST component
hardware part of a MOST device (3.41)
Note 1 to entry: MOST components are, for example, EOC, OEC, MNC, and pigtail. A MOST component can consist
of other MOST components.
3.41
MOST device
electronic control unit (3.22) that contains optical or electrical MOST components (3.40)
3.42
MOST module
MOST components (3.40) that consists of multiple MOST components
3.43
MOST network
communication network connecting MOST devices (3.41)
3.44
MOST network controller
MNC
MOST components (3.40) that performs routing and manages MOST network (3.43) resources
3.45
MOST network service
intermediate layer providing routines to simplify the handling of the MOST network controller (3.44)
3.46
MOST node
entity in the MOST network (3.43) with an assignable logical node address (3.36) and an implemented
MOST network service (3.45) library
3.47
MOST output
output of the MOST network controller (3.44)
3.48
MOST port
MOST network controller's (3.44) connection point to the MOST transceiver (3.49)
3.49
MOST transceiver
transceiver for the MOST network (3.43)
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3.50
multi-node device
MOST device (3.41) that contains more than one node (3.57)
3.51
NetInterface
communication section of the TimingMaster (3.81) or a TimingSlave (3.83)
3.52
network activity
presence of valid MOST data (3.89) at the input
3.53
network change event
NCE
event that indicates a change of the visible nodes (3.57) value
3.54
network frame
underlying frame (3.26) for all other frame types in the MOST network (3.43)
3.55
network frame rate
Fs
periodic repetition frequency of the network frame (3.54)
Note 1 to entry: The default sampling frequency and the network frame rate in a MOST network (3.43) are
identical. Therefore, the abbreviation Fs is used.
3.56
network owner
entity that is responsible for the initial integrity of the network at design time
3.57
node
TimingMaster (3.81), TimingSlave (3.83), or listen-only node (3.33)
3.58
node position address
addresses that is based on the node (3.57) counter value
3.59
packet channel
channel (3.10) that is used to transport packet data (3.60)
3.60
packet data
anisochronous (3.4) data packets
3.61
phase variation
time deviation between the edges of a real signal and the edges of a reference signal (3.63)
3.62
probability density function
PDF
for the distribution function f of the argument x, derivative df(x)/dx
[SOURCE: IEC Electropedia, 103-08-09, modified — The term "probability density" was deleted.]
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3.63
reference signal
ideal signal formed according to the reference time base (3.64)
3.64
reference time base
network frame rate (3.55) as defined by the crystal oscillator of the TimingMaster (3.81)
3.65
remote-controlled node
TimingSlave (3.83) that is not required to implement the MOST network service (3.45)
3.66
rise time
interval of time between the instants at which the instantaneous value of a pulse first reaches a
specified lower value and then a specified upper value
[SOURCE: IEC Electropedia, 702-03-05, modified — Note 1 to entry was deleted.]
3.67
segment
control frame (3.15) in a segmented transfer
3.68
serial data analyser
SDA
instrument used to perform industry standard jitter (3.31) and amplitude measurements and
operations on a serial data stream
3.69
shutdown flag
flag that indicates an imminent shutdown
3.70
simplex
pertaining to a method of operation in which information can be transmitted in either direction, but
not simultaneously, between two points
[SOURCE: IEC Electropedia, 701-03-161, modified — The deprecated term "half-duplex" was deleted.]
3.71
source address
logical node address (3.36) of the sender
3.72
source data
streaming data (3.75) and packet data (3.60)
3.73
specification point
SP[n]
interface that is a boundary between a transmitting and a receiving MOST component (3.40)
3.74
streaming connection
reserved bandwidth on the network identified by a connection label (3.12)
3.75
streaming data
content, such as audio or video data, which is transmitted synchronously (3.77) or isochronously (3.29)
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3.76
sudden signal off
SSO
unexpected disappearance of network activity (3.52)
3.77
synchronous
qualifying two time-varying phenomena, time-scales, or signals characterized by corresponding
significant instants which are separated by time intervals of a constant desired duration
Note 1 to entry: In practice, any variations of the time intervals are constrained within specified limits.
Note 2 to entry: Two phenomena, time-scales, or signals may be synchronous without being isochronous (3.29).
Note 3 to entry: For periodic phenomena, time-scales or signals, the corresponding significant instants occur at
the same average rate.
[SOURCE: IEC Electropedia, 704-13-15]
3.78
synchronous channel
channel (3.10) that is used to transport synchronous (3.77) data on the network frame (3.54)
3.79
target address
node position address (3.58), logical address, or group address
3.80
telegram
single control frame (3.15)
3.81
TimingMaster
provider of the network clock
3.82
TimingMaster delay tolerance
T
MDT
maximum amount of propagation delay through the MOST network (3.43) that the TimingMaster (3.81)
accepts without failure
3.83
TimingSlave
node (3.57) that obtains the network clock from the MOST network (3.43)
3.84
transferred jitter
TJ
jitter (3.31) that is propagated through the network
3.85
transferred wander
wander (3.90) that is propagated through the network
3.86
uncorrelated jitter
jitter (3.31) that is not correlated to any other jitter (3.31) source in the MOST network (3.43)
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3.87
unit interval
UI
longest time interval such that the rated durations of the significant intervals of a signal are all whole
multiple of the duration of this interval
[SOURCE: IEC Electropedia, 721-02-32, modified — The term "signal element" was deleted.]
3.88
unlock
failure to receive an aligned PREAMBLE at the correct bit location for two consecutive frames (3.26),
once locked
3.89
valid MOST data
direct-current-adaptive-encoded data that meets defined link (3.32) quality parameters and bit rate
(3.6) requirements
3.90
wander
long-term non-cumulative variations in the significant instants of a digital signal from their ideal
positions in time
[SOURCE: IEC Electropedia, 704-16-14]
4 Symbols and abbreviated terms
4.1 Symbols
--- empty cell/undefined
4.2 Abbreviated terms
AJ alignment jitter
AL application layer
API application programming interface
BR bit rate
CL connection label
CT conformance test
CTC conformance test case
CTP conformance test plan
DLL data link layer
DTCP Digital Transmission Content Protection
ECU electronic control unit
ePHY electrical physical layer
FBlock function block
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Fs network frame rate
HDCP High-bandwidth Digital Content Protection
IUT implementation under test
LSb least significant bit
LT lower tester
MNC MOST network controller
MOST Media Oriented Systems Transport
MSb most significant bit
NCE network change event
NL network layer
oPHY optical physical layer
PHY physical layer
PL presentation layer
PLL phase locked loop
POF plastic optical fibre
QoS quality of service
REQ requirement
SL session layer
SSO sudden signal off
STP shielded twisted pair
TDM time-division-multiplexing
TJ transferred jitter
TL transport layer
UT upper tester
UTP unshielded twisted pair
5 Access to MOST specification versions
5.1 General
The ISO standards maintenance portal provides references to the normative and supplemental MOST
specifications. The documents listed in Annex A shall be applied for the selected MOST version. The
documents listed in Annex B contain additional information for the selected MOST version. These
documents comprise different MOST versions:
— MOST version 4V0 specifications are referenced by the ISO 21806 series. Under ISO conformance,
deviations are managed between the manufacturers. The ISO 21806 series is technically equivalent.
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— MOST version 3V1 specifications are referenced by the ISO 21806 series. Under ISO conformance,
deviations are managed between the manufacturers. The ISO 21806 series is technically equivalent.
— MOST version 3V0 specifications are only referenced by this document. MOST version 3V0
implementations shall be in accordance with MOST Specification Rev. 3.0.0E2, 07/2010. The
compliance test specifications in the MOST version 3V0 are used for conformance testing according to
this document (“conformity according to ISO 21806-1, MOST version 3V0”). Under ISO conformance,
deviations are managed between the manufacturers.
— MOST version 2V5 specifications are only referenced by this document. MOST version 2V5
implementations shall be in accordance with MOST Specification Rev. 2.5.0, 10/2006. The compliance
test specifications in the MOST version 2V5 are used for conformance testing according to this
document (“conformity according to ISO 21806-1, MOST version 2V5”). Under ISO conformance,
deviations are managed between the manufacturers.
5.2 ISO standards maintenance portal
The ISO standards maintenance portal is accessible using this URL: https:// standards .iso .org/ iso/
21806/ -1/ ed -1/ en.
Figure 3 shows where the document, for example "Access_To_MOST_Versions_2019-07.pdf", is located.
The "Access_To_MOST_Versions_2019-07.pdf" document contains hyperlinks to the content that is listed
in Annex A and Annex B.
Figure 3 — Overview of directory structure
The "Access_To_MOST_Versions_2019-07.pdf" document filename is modified each time a newer version
is available. The release date (year: 2019, month: July) is encoded in the filename.
EXAMPLE "Access_To_MOST_Versions_2020-01.pdf" is an example of a document released in January 2020.
5.3 MOST versions directory structure
Figure 4 illustrates the MOST versions directory structure as listed in Annex A and Annex B.
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Figure 4 — MOST versions directory structure
st nd
The general directory structure consi
...