IEC 62106-10:2021

IEC 62106-10 ®
Edition 1.0 2021-11
INTERNATIONAL
STANDARD
Radio data system (RDS) – VHF/FM sound broadcasting in the frequency range
from 64,0 MHz to 108,0 MHz –
Part 10: UECP – Universal Encoder Communication Protocol
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IEC 62106-10 ®
Edition 1.0 2021-11
INTERNATIONAL
STANDARD
Radio data system (RDS) – VHF/FM sound broadcasting in the frequency range

from 64,0 MHz to 108,0 MHz –
Part 10: UECP – Universal Encoder Communication Protocol

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.060.01; 33.160.20; 33.170 ISBN 978-2-8322-1042-4

– 2 – IEC 62106-10:2021 © IEC 2021
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions and abbreviated terms . 9
3.1 Terms and definitions. 9
3.2 Abbreviated terms . 10
4 RDS encoder hardware model . 10
5 RDS encoder software model . 12
6 Destination addressing method . 13
6.1 General . 13
6.2 Site address. 14
6.3 Encoder address . 15
7 Transmission modes . 15
7.1 General . 15
7.2 Uni-directional mode . 15
7.3 Bi-directional mode, requested response . 15
7.4 Bi-directional mode, spontaneous response . 15
8 Protocol description . 15
8.1 Data format . 15
8.2 Data link layer . 15
8.2.1 General . 15
8.2.2 Data-frame . 16
8.2.3 Byte-stuffing method . 19
8.2.4 Message field format . 19
8.3 Message codes . 21
8.3.1 General . 21
8.3.2 Remote and configuration commands . 21
8.3.3 RDS messages . 21
8.3.4 Handling of RDS message bits declared "rfu" . 21
8.3.5 Status messages . 21
8.3.6 Specific messages . 21
8.4 Description of data handling . 21
8.5 Group sequence configuration . 22
8.5.1 Basic principles used . 22
8.5.2 Group sequence determination . 22
8.5.3 Extended group sequence command . 22
8.5.4 Relative priority group sequence command . 22
8.5.5 Special transmission conditions . 22
8.6 Handling of ODA data . 23
8.6.1 Using ODAs on data-stream 0 . 23
8.6.2 Using ODAs on the upper data-streams 1 to 3 . 23
Annex A (normative) UECP message command repertoire . 26
A.1 Message command format . 26
A.2 Commands for A or B-type groups on data-stream 0 . 26
A.2.1 PI / MEC 0x01 . 26

A.2.2 PS / MEC 0x02 . 27
A.2.3 Long PS / MEC 0x21 . 28
A.2.4 Data group for PTYI / MEC 0x04 . 28
A.2.5 TP – TA / MEC 0x03 . 29
A.2.6 PTY / MEC 0x07 . 29
A.2.7 PTYN / MEC 0x3E . 30
A.2.8 RT / MEC 0x0A . 30
A.2.9 AF / MEC 0x13 . 33
A.2.10 EON-AF / MEC 0x14 . 34
A.2.11 ECC and other slow label settings / MEC 0x1A . 35
A.2.12 Linkage information / MEC 0x2E . 36
A.2.13 Free-format data in type A or B group / MEC 0x24 . 36
A.3 Commands for ODAs on data-stream 0 . 37
A.3.1 Group type 3A ODA configuration and short message command / MEC
0x40 . 37
A.3.2 ODA assignment group usage sequence signalling / MEC 0x41 . 39
A.3.3 ODA relative priority group sequence / MEC 0x43 . 40
A.3.4 ODA data group repetitions and burst mode / MEC 0x44 . 40
A.3.5 ODA "spinning wheel" timing control / MEC 0x45 . 41
A.3.6 ODA data / MEC 0x46 . 42
A.3.7 ODA data command access right / MEC 0x47 . 44
A.4 Commands for clock setting and control for data-stream 0 . 45
A.4.1 Real time clock for CT / MEC 0x0D . 45
A.4.2 Real time clock correction for CT / MEC 0x09 . 46
A.4.3 CT on-off command / MEC 0x19 . 46
A.5 Commands for RDS signal alignment and control on data-stream 0 . 47
A.5.1 RDS on-off command data-stream 0 / MEC 0x1E . 47
A.5.2 RDS phase for subcarrier 0 / MEC 0x22 . 47
A.5.3 RDS level for subcarrier 0 / MEC 0x0E . 48
A.6 Message name commands control and set-up commands on data-stream 0 . 49
A.6.1 Site address / MEC 0x23 . 49
A.6.2 Encoder address / MEC 0x27 . 49
A.6.3 Make PSN list / MEC 0x28 . 50
A.6.4 PSN enable-disable / MEC 0x0B . 50
A.6.5 EON elements enable-disable / MEC 0x3F . 51
A.6.6 Communication mode / MEC 0x2C. 52
A.6.7 TA control / MEC 0x2A . 53
A.6.8 EON-TA control / MEC 0x15 . 53
A.6.9 Reference input select / MEC 0x1D . 54
A.6.10 Data set select / MEC 0x1C . 54
A.6.11 Group sequence determination for data-stream 0 / MEC 0x16 . 54
A.6.12 Extended group sequence for data-stream 0 / MEC 0x38 . 55
A.6.13 Group variant code sequence for data-stream 0 / MEC 0x29 . 57
A.6.14 Encoder access right / MEC: 0x3A . 58
A.6.15 Communications port configuration – Mode / MEC 0x3B . 59
A.6.16 Communications port configuration – Speed / MEC 0x3C . 60
A.6.17 Communications port configuration – Timeout /MEC 0x3D . 62
A.6.18 Message acknowledgment / MEC 0x18 . 63
A.6.19 Request message / MEC 0x17 . 64

– 4 – IEC 62106-10:2021 © IEC 2021
A.7 Manufacturers' and transmission operators' specific command / MEC 0x2D . 65
A.8 Commands for the C-type groups used on data-streams 1 to 3 . 66
A.8.1 ODA-AID channel assignment for AS group type C (Alternative 1)/MEC
0x50 . 66
A.8.2 ODA-AID channel assignment for AS group type C (Alternative 2) / MEC

0x51 . 68
A.8.3 Relative priority group sequence / MEC 0x53 . 71
A.8.4 Burst mode control for ODA group type C / MEC 0x54 . 71
A.8.5 RFT file data transfer (Alternative 2)/MEC 0x55 . 72
A.8.6 ODA data group command / MEC 0x56 . 73
A.8.7 RFT file data transfer and associated data for the assignment group(s)

variants 0 and 1 (Alternative 1) / MEC 0x57 . 75
A.8.8 File associated data for AS group variants 2 to 7 (Alternative 1)/MEC
0x58 . 76
A.8.9 Define in the RFT a file sequence for the AID/MEC 0x59 . 78
A.8.10 Define the group sequence / MEC 0x61 . 79
A.8.11 Extended group sequence for group type C/MEC 0x83 . 80
A.8.12 Upper data-stream level / MEC 0xE0 . 82
A.8.13 Upper data-streams on – off/MEC 0xE1 . 82
Annex B (normative) UECP transmission over IP networks . 84
Annex C (informative) Transport of UECP data within DVB-S radio . 85
Annex D (informative) Manufacturer and transmission operator command code
registration . 86
Annex E (informative) Listing of Message Element Codes . 87
Annex F (informative) Special optional ODA transmission mode on RDS data-stream 0
with group type A or B . 89
F.1 "Burst mode" transmission . 89
F.2 "Spinning wheel" mode transmission . 89
Annex G (normative) Message Element Codes kept for backwards compatibility on
data-stream 0 . 90
G.1 General . 90
G.2 ODA data group/MEC 0x42 . 90
G.3 EWS / MEC 0x2B . 91
G.4 TDC/MEC 0x26 . 92
G.5 TMC / MEC 0x30 . 93
G.6 DAB Dynamic label message – DL/MEC 0xAA . 93
G.7 DAB Dynamic label command/MEC 0x48 . 94
Annex H (informative) Example for defining the group sequence for data-stream 0
including ODA groups . 96
Annex I (informative) Example of how to send a logo with two different resolutions
using RFT . 97
I.1 Send files to the encoder . 97
I.1.1 General . 97
I.1.2 Alternative 1: using MECs 0x50 and 0x57 . 97
I.1.3 Alternative 2: using MECs 0x51 and 0x55 . 98
I.2 Data-stream number setting . 100
I.3 File sequence setting . 100
Bibliography . 101

Figure 1 – RDS encoder hardware model . 11
Figure 2 – RDS encoder software model . 13
Figure 3 – Fictitious example of site addressing . 14
Figure 4 – UECP data-frame format . 16
Figure 5 – UECP data frame with the CRC-16 for example 1 being 0x25F4 . 18
Figure 6 – UECP data frame with the CRC-16 for example 2 being 0x800C . 19
Figure A.1 – Message transmission cycle diagram . 32
Figure F.1 – "Spinning wheel" mode – one minute transmission cycle that starts with a
4A group . 89

Table 1 – UECP data-frame description . 16
Table 2 – Byte-stuffing method . 19
Table 3 – Message structure . 20
Table 4 – Data set number . 20
Table 5 – Programme Service Number . 21
Table A.1 – Message command format . 26

– 6 – IEC 62106-10:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RADIO DATA SYSTEM (RDS) –
VHF/FM SOUND BROADCASTING IN THE FREQUENCY
RANGE FROM 64,0 MHz TO 108,0 MHz –

Part 10: UECP – Universal Encoder Communication Protocol

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62106-10 has been prepared by technical area 1: Terminals for
audio, video and data services and content, of IEC technical committee 100: Audio, video and
multimedia systems and equipment.
This first edition, together with IEC 62106-1, IEC 62106-2, IEC 62106-3, IEC 62106-4,
IEC 62106-5, IEC 62106-6 and IEC 62106-9, cancels and replaces IEC 62106:2015, and
constitutes a technical revision.
This edition includes the following significant technical changes with respect to IEC 62106:2015:
• The Universal Encoder Communication protocol UECP adapted to support optional RDS2 is
new.
• The section dealing with legacy RDS using data-stream 0 only is a transcription of an RDS
Forum technical specification which was initially developed by the EBU and which was
th
already in its 7 version [1]. Full backwards compatibility with previous versions was
maintained, but RDS features no longer specified in IEC 62106-2 were deleted.

The text of this International Standard is based on the following documents:
Draft Report on voting
100/3643/FDIS 100/3688/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 62106 series, published under the general title Radio data system
(RDS) – VHF/FM sound broadcasting in the frequency range from 64,0 MHz to 108,0 MHz), can
be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 8 – IEC 62106-10:2021 © IEC 2021
INTRODUCTION
Since the mid-1980s a fascinating development has taken place. Most of the multimedia
applications and standards have been created or redefined significantly. Hardware has become
extremely powerful with dedicated software and middleware. In the mid-1980s, Internet as well
as its protocols did not exist. Navigation systems became affordable in the late 1990s, and a
full range of attractive smartphones now exist. The computing power of all these new products
is comparable with that of the mainframe installations in that era.
Listener expectations have grown faster than the technology. Visual experience is now very
important, like the Internet look and feel. Scrolling text or delivering just audio is nowadays
perceived as insufficient for FM radio, specifically for smartphone users. New types of radio
receivers with added value features are therefore required. RDS has so far proven to be very
successful.
FM radio with RDS is an analogue-digital hybrid system, which is still a valid data transmission
technology and only the applications need adaptation. Now the time has come to solve the only
disadvantage, the lack of sufficient data capacity. With RDS2, the need to increase the data
capacity can be fulfilled.
RDS was introduced in the early 1980s. During the introductory phase in Europe, the car
industry became very involved and that was the start of an extremely successful roll-out. Shortly
afterwards, RDS (RBDS) was launched in the USA [2, 3, 4, 5, 6].
The RDS Forum has investigated a solution to the issue of limited data capacity. For RDS2,
both sidebands around the RDS 57 kHz subcarrier can be repeated a few times, up to three,
centred on additional subcarriers higher up in the FM multiplex still remaining compatible with
the ITU Recommendations.
The core elements of RDS2 are the additional subcarriers, which will enable a significant
increase of RDS data capacity to be achieved, and then only new additional data applications
will have to be created, using the RDS-ODA feature, which has been part of the RDS standard
IEC 62106 for many years.
In order to update IEC 62106:2015 to the specifications of RDS2, IEC 62106 has been
restructured as follows:
Part 1: Modulation characteristics and baseband coding
Part 2: RDS message format, coding and definition of RDS features
Part 3: Usage and registration of Open Data Applications ODAs
Part 4: Registered code tables
Part 5: Marking of RDS and RDS2 devices
Part 6: Compilation of technical specifications for Open Data Applications in the public domain
Part 9: RBDS – RDS variant used in North America
Part 10: Universal Encoder Communication Protocol UECP
NOTE 1 The Part numbers 7 and 8 will not be used.
The original specifications of the RDS system have been maintained and the extra
functionalities of RDS2 have been added.
Obsolete or unused functions from the original RDS standard have been deleted.
_______________
Numbers in square brackets refer to the Bibliography.

RADIO DATA SYSTEM (RDS) –
VHF/FM SOUND BROADCASTING IN THE FREQUENCY
RANGE FROM 64,0 MHz TO 108,0 MHz –

Part 10: UECP – Universal Encoder Communication Protocol

1 Scope
This part of IEC 62106 describes the Universal Encoder Communication Protocol – UECP. The
UECP has as its primary objectives to satisfy the need for harmonized RDS encoder
communication protocols and to facilitate the interworking of various RDS systems components,
such as RDS servers, data bridges and encoders, regardless of the supplier. Furthermore, a
harmonised network environment and encoder model is being maintained to facilitate the
interchange of component parts of RDS network systems. These harmonized models and a
universal layered protocol are specified, based on the ISO/OSI recommendation. The UECP
encompasses all current RDS features including any new developments using the ODA protocol.
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.
IEC 62106-1, Radio data system (RDS) – VHF/FM sound broadcasting in the frequency range
from 64,0 MHz to 108,0 MHz – Part 1: Modulation characteristics and baseband coding
IEC 62106-2:2021, Radio data system (RDS) – VHF/FM sound broadcasting in the frequency
range from 64,0 MHz to 108,0 MHz – Part 2: Message format: Coding and definition of RDS
features
IEC 62106-4, Radio data system (RDS) – VHF/FM sound broadcasting in the frequency range
from 64,0 MHz to 108,0 MHz – Part 4: Registered code tables
ETSI EN 300 401, Radio Broadcasting Systems; Digital Audio Broadcasting (DAB) to mobile,
portable and fixed receivers
ETSI TS 101 756, Digital Audio Broadcasting (DAB); Registered Tables
ETSI TS 102 980, Digital Audio Broadcasting (DAB); Dynamic Label Plus (DL Plus); Application
specification
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms, definitions and abbreviated terms of IEC 62106-1,
of IEC 62106-2 and the following apply.

– 10 – IEC 62106-10:2021 © IEC 2021
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Abbreviated terms
ADD Destination address bytes (2 bytes)
AS Assignment signalling (assign channel/pipe to AID) for RDS2
CRC-16 Cyclic Redundancy Check (2 bytes)
DAB Digital Audio Broadcasting
DL Dynamic Label (DAB)
DSN Data Set Number
DVB-S Digital Video Broadcasting via Satellite
ID Identification
IP Internet Protocol
GS Group sequence
MEC Message Element Code
MED Message Element Data
MEL Message Element data Length
MFL Message Field Length
MSG Message bytes
PSN Programme Service Number
RFT RDS2 File Transfer protocol
SQC Sequence counter byte
STA Start byte
STP Stop byte
TCP Transmission Control Protocol used on the Internet
UDP User Datagram Protocol used on the Internet
UECP Universal Encoder Communication Protocol
4 RDS encoder hardware model
A simplified model of an RDS encoder with data-stream 0 and three optional upper data-streams
1 – 3 is shown in Figure 1. The model does not include such obvious or necessary components
as a power supply or control panel, but includes the blocks necessary to understand and
develop the protocol itself.
These blocks are:
• Processor – the central processing unit of the encoder, usually a micro-processor, with
access to input and output devices, the real-time clock, and memory.
• Memory – comprises ROM and RAM necessary for the operating software of the encoder,
and appropriate RAM, NVRAM, and ROM for stored data.
• Real time clock – maintains the current time of day and calendar date. Used to generate
type 4A groups (CT).
• Communication interface – UECP data using this specification is received from an RDS data
server of the broadcaster or a transmission operator and transmitted using the serial
communications interface. Alternatively, an IP interface may be used. The appropriate IP
transmission methods are described in Annex B.
• RDS modulator – produces the RDS bi-phase signal, in accordance with IEC 62106-1.
• 57 kHz subcarrier – frequency and phase locked to the third harmonic of the selected 19 kHz
pilot-tone reference source.
• 66,5 kHz subcarrier – frequency and phase locked to the third harmonic of the selected
19 kHz pilot-tone reference source and used to generate data-stream 1.
• 71,25 kHz subcarrier – frequency and phase locked to the third harmonic of the selected
19 kHz pilot-tone reference source and used to generate data-stream 2.
• 76 kHz subcarrier – frequency and phase locked to the third harmonic of the selected 19 kHz
pilot-tone reference source and used to generate data-stream 3.
• Reference selector (optional): selects one source of the 19 kHz pilot-tone reference signal,
out of a maximum of six, to lock to the internal 57 kHz oscillator. Each 19 kHz reference
source corresponds to a specific level and phase adjustment of the produced output signal.
When a specific reference source is selected via the Reference selector, the corresponding
level and phase values are taken from a "reference entry table". This table comprises the
following parameters:RDS output level for each of the data-streams (see IEC 62106-1).
• RDS subcarrier 0 phase relative to the pilot (see IEC 62106-1 for conditions to be met).
• Level and phase control: the level of each subcarrier and phase of subcarrier 0 shall be
adjusted by the processor under the appropriate commands (see Annex A). The phase of
subcarriers 1, 2, and 3 shall be phase locked to subcarrier 0 (see IEC 62106-1). The output
level shall be set in the range 0 mV to 8 191 mV, and the phase in the range between 0°
and 360° to lock to the internal 57 kHz oscillator. Level and phase of the RDS signal may
depend of the 19 kHz pilot-tone reference signal. As up to six reference inputs may be used,
level and phase are set on the "reference table entry", as mentioned under the item
"Reference selector" above.
Figure 1 – RDS encoder hardware model

– 12 – IEC 62106-10:2021 © IEC 2021
5 RDS encoder software model
The encoder in accordance with the addressing method described in Clause 6 accepts
messages, which are detailed in Clause 8. Applicability is further determined by optional fields
within the message itself. This permits addressing of the structures shown in Figure 2:
• Data sets: an encoder will have one or more data sets identified by a unique DSN, each of
which results in a particular RDS output. Each data set may refer to many programme
services using the RDS-EON feature. Only one data set is responsible at any one time for
the encoder's output and is known as the current data set. Data sets are addressed by the
protocol as described in Clause 8.
• Programme services: all programme services are identified by a unique Programme Service
Number PSN which is used to label data within RDS networks. In a network providing the
EON feature, data for several programme services will be sent to an encoder, which can
then identify that the data refers to one or more of the data sets and elements within the
data sets used by that encoder. Programme services are addressed using the PSN by the
protocol as described in Clause 8. There is a specific memory area in each data set for each
programme service.
• Buffers: some information is buffered, for example ODAs, EWS and other free format
groups. This means that the received information is placed in a queue awaiting transmission.
It is possible to configure a buffer for cyclic transmission.
On the upper data-streams for RDS2, only C-type groups are used. For A and B type groups
on the upper data-streams, C-type tunneling shall be used (see IEC 62106-2).

Figure 2 – RDS encoder software model
6 Destination addressing method
6.1 General
Communication to RDS encoders needs to be capable of many levels of addressing: to all
encoders, to specific sets of encoders, or to a particular device. This may be accomplished by
unique physical connections or by a suitable logical addressing method.

– 14 – IEC 62106-10:2021 © IEC 2021
It is expected that many messages will be sent to all encoders. Thus, the global number of "0"
is defined for both the site and encoder addresses. Messages bearing the global site address
are deemed to be acceptable at all sites in the system. Messages bearing the global encoder
address are deemed to be acceptable at all encoders at sites specified by the accompanying
site address.
An encoder will have two destination address lists, one of acceptable site addresses and the
other of acceptable encoder addresses; see Figure 2. The site address list includes "0" (the
global site address), the unique site address and any additional site group addresses. The
encoder address list includes "0" (the global encoder address), the unique encoder address
and any additional encoder group addresses.
A message is acceptable to a particular encoder only if the site address is contained within its
site address list and the encoder address is contained within its encoder address list.
The site and encoder addresses should be thought of as being entirely physical and are used
only to address a certain "box" at a certain location; the functionality of the "box" is irrelevant
in this context.
6.2 Site address
In defining an environmental model for the UECP the following assumptions are made:
• The data-stream will feed one or more transmitter sites. Each site will have a unique
address, known as the site address (a number in the range 1 to 1 023). All encoders at a
particular transmitter site share the same site address.
• An encoder will possess one or more site addresses. One of these shall be unique to the
particular physical site location. Additional site addresses are permitted for a particular area,
region, or country.
To clarify this concept, an example is given in Figure 3.

Figure 3 – Fictitious example of site addressing
All encoders at the NEWTOWN site have the unique site address "123". Other encoders in the
system are not permitted to use this address. Encoders at the NEWTOWN site also have the
site address "267", which is allocated to all encoders in the LAKE VALLEY area. Messages
arriving at the NEWTOWN site with either of these two site addresses will be accepted.
Messages arriving at the LITTLE VILLAGE site (address "452"), also in the LAKE VALLEY area,
will not be accepted if they carry the NEWTOWN site address, but will be accepted if they carry
either the LITTLE VILLAGE or the LAKE VALLEY site addresses.

6.3 Encoder address
Several RDS encoders are installed at each transmitter site, serving a number of programme
services. Backup equipment is sometimes provided, sometimes not. A single backup encoder
can even be provided for several programme services. Whatever the situation may be, each
encoder at the site needs to be individually addressable. A second level of addressing is
therefore introduced, the encoder address (a number in a range 1 to 63).
An encoder will possess one or more encoder addresses. One shall be unique to the encoder
at that site. Additional encoder addresses may be assigned in accordance with the encoder's
usage or manufacture. However, the site and encoder addresses are not intended to specify a
particular radio service.
7 Transmission modes
7.1 General
The UECP protocol is designed to operate using serial communication.
The communication is always the same, regardless of which mode will be used. Whether the
transmission mode is then taken as I2C, RS232, USB, UDP/TCP (see Annex B), or DVB-S
(see Annex C), the transmitting device itself does not change the UECP protocol (see
Clause 8).
7.2 Uni-directional mode
This mode is used on one-way communication links. Data is transmitted to one, a group, or all
encoders. Response from the encoder is not possible.
7.3 Bi-directional mode, requested response
This mode uses a two-way communication link to transmit data to one, a group or all encoders.
It allows the RDS server to request data, status, and error report from encoders.
7.4 Bi-directional mode, spontaneous response
A two-way communication link allows UECP software to transmit data to encoders and request
data from encoders. Encoders are also able to spontaneously generate status and error
messages. Such messages, their content and application are described in Annex A (MEC 0x18).
8 Protocol description
8.1 Data format
The data is transmitted byte by byte in asynchronous mode. In short it is: Start byte STA; then
stuffed data bytes (as described in 8.2.3); then terminated by the end Stop byte STP.
8.2 Data link layer
8.2.1 General
Update data comprises a stream of data-frames. A frame comprises a series of bytes, delimited
by the two reserved bytes, STA (Start) and STP (Stop), which mark the beginning and end of
the frame. Each frame contains a destination address (ADD), defining the set of encoders to
which the message is being sent. A sequence counter (SQC) labels each separate record. The
message itself is preceded by the MFL byte defining the message field length and it is followed
by the two CRC-16 checkword bytes.

– 16 – IEC 62106-10:2021 © IEC 2021
The Start and Stop bytes are uniquely defined and may not occur in any other field of a frame.
In order to prevent this, a frame is byte-stuffed prior to transmission. Byte-stuffing transforms
an occurrence of a reserved byte into two bytes (see 8.2.3). The reverse process is applied at
reception, where byte-stuffed frames are converted prior to frame processing. Thus, although
the Start and Sto
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