IEC 60728-7-3:2003

Cable networks for television signals, sound signals and interactive services - Part 7-3: Hybrid fibre coax outside plant status monitoring - Power supply to transponder interface bus (PSTIB) specification

specifies requirements for the Hybrid Fibre Coax (HFC) Outside Plant (OSP) Power Supplies (PS). This standard is part of a series developed to support the design and implementation of interoperable management systems for evolving HFC cable networks. The purpose of the standards is to support the design and implementation of interoperable management systems for evolving HFC cable networks. The Power Supply to Transponder Interface Bus (PSTIB) specification describes the physical (PHY) interface and related messaging and protocols implemented at the Data Link Layer (DLL), layers 1 and 2 respectively in the 7-layer ISO-OSI reference model, that support communications between compliant transponders and the managed OSP power supplies and other related power equipment to which they interface.

General Information

• Status: Published
• Publication Date: 07-Oct-2003
• ICS: 33.040.40 - Data communication networks
• ICS: 33.160.01 - Audio, video and audiovisual systems in general
• Technical Committee: TC 100 - Audio, video and multimedia systems and equipment
• Current Stage: DELPUB - Deleted Publication
• Start Date: 13-Oct-2009
• Completion Date: 14-Feb-2026

Relations

• Revised: IEC 60728-7-3:2009 - Cable networks for television signals, sound signals and interactive services - Part 7-3: Hybrid fibre coax outside plant status monitoring - Power supply to transponder interface bus (PSTIB)
• Effective Date: 05-Sep-2023

Overview

IEC 60728-7-3:2003 - "Cable networks for television signals, sound signals and interactive services - Part 7-3: Hybrid fibre coax outside plant status monitoring - Power supply to Transponder Interface Bus (PSTIB) specification" - defines the interface and messaging required to manage power equipment in Hybrid Fibre Coax (HFC) outside plant (OSP). The standard specifies the Physical (PHY) layer and Data Link Layer (DLL, ISO‑OSI layers 1 and 2) that enable communications between managed OSP power supplies (PS), related power equipment (batteries/generators) and compliant transponders.

Key topics and technical requirements

• Scope and purpose: Requirements for HFC OSP power supplies to support interoperable management systems for evolving cable networks.
• PHY and DLL definitions: Physical interface signals and link-layer protocols needed for reliable PSTIB communication between transponders and power equipment.
• Transponder classifications: Defines type classifications (Type 0–3) and focuses on interoperability with Type 2 and Type 3 compliant transponders.
• Messaging and datagrams: Standardizes DLL packet structures and a set of datagrams/commands used for status reporting and control. Example command/response datagrams included (e.g., Get_Configuration, Get_Power_Supply_Data, Power_Supply_Control, Get_Generator_Data, Generator_Control).
• Interface examples and connectors: Includes PHY examples (e.g., RS‑485 electrical characteristics referenced via EIA RS‑485) and connector/pin assignments (illustrative tables such as RJ‑45 pinout).
• Timing and protocol rules: Defines interface timing, packet framing, addressing ranges and error/response datagrams for robust OSP communications.
• Compliance and revision control: Requirements for interface and implementation compliance and how revisions are managed.

Practical applications and who uses it

• Cable network operators / MSOs: For remote monitoring and management of OSP power systems (rectifiers, batteries, generators) in CATV/HFC networks.
• Equipment manufacturers: To design compliant OSP power supplies, transponders and power-management modules that interoperate across vendors.
• System integrators and installers: To implement PSTIB wiring, PHY connections (e.g., RS‑485 interfaces) and management interfaces in outside plant deployments.
• NOC and maintenance teams: For alarm, status polling and remote control of power equipment to improve reliability and reduce truck rolls.
• Test, certification and compliance labs: To verify device conformance to PHY/DLL behaviors and interoperability.

Keywords: IEC 60728-7-3:2003, PSTIB, HFC outside plant, power supply to transponder interface, Data Link Layer, physical layer, RS‑485, OSP power monitoring, transponder communications, interoperable management systems.

Related standards

• IEC 60728 series (other parts covering HFC network components and management)
• EIA RS‑485 (normative reference for balanced multipoint electrical characteristics)

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD
60728-7-3
First edition
2003-10
Cable networks for television signals,
sound signals and interactive services –
Part 7-3:
Hybrid Fibre Coax Outside Plant
Status Monitoring –
Power supply to Transponder Interface
Bus (PSTIB) Specification
Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the

60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.

Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,

edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the

base publication incorporating amendment 1 and the base publication incorporating

amendments 1 and 2.
Further information on IEC publications
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology. Information relating to
this publication, including its validity, is available in the IEC Catalogue of
publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is also available from the following:
• IEC Web Site (www.iec.ch)
• Catalogue of IEC publications
The on-line catalogue on the IEC web site (www.iec.ch/searchpub) enables you to
search by a variety of criteria including text searches, technical committees
and date of publication. On-line information is also available on recently issued
publications, withdrawn and replaced publications, as well as corrigenda.
• IEC Just Published
This summary of recently issued publications (www.iec.ch/online_news/ justpub)
is also available by email. Please contact the Customer Service Centre (see
below) for further information.
• Customer Service Centre
If you have any questions regarding this publication or need further assistance,
please contact the Customer Service Centre:

Email: [e-mail]
Tel: [phone]
Fax: [phone]
INTERNATIONAL IEC
STANDARD
60728-7-3
First edition
2003-10
Cable networks for television signals,
sound signals and interactive services –
Part 7-3:
Hybrid Fibre Coax Outside Plant
Status Monitoring –
Power supply to Transponder Interface
Bus (PSTIB) Specification
 IEC 2003  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
U
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – 60728-7-3  IEC:2003(E)
CONTENTS
FOREWORD . 4

INTRODUCTION .6

1 Scope . 7

2 Normative references. 8

3 Terms, definitions and abbreviations. 8

3.1 Terms and definitions . 8

3.7 Abbreviations. 8
4 Reference architecture forward and return channel specifications. 9
5 Power supply to transponder interface bus specification overview . 9
5.1 Interface compliance.10
5.2 Implementation compliance .10
5.3 Revision control.10
6 Power supply to transponder interface bus – Physical layer specification.10
6.1 Interface requirements.10
6.2 Interface diagram.12
7 Power supply to transponder interface bus – Data link layer specification .13
7.1 DLL packet structure.13
7.2 DLE sequence .15
7.3 Interface timing.15
7.4 DLL datagrams .17
Figure 1 – Reference architecture diagram. 9
Figure 2 – Sample PSTIB RS-485 interface.13
Figure 3 – DLL packet structure .14
Figure 4 – PSTIB Data and timing diagram.16
Figure 5 – DLL datagram structure.17
Figure 6 – Battery string naming conventions.27
Table 1 – Transponder type classifications. 7
Table 2 – RJ-45 Connector pin assignment .11

Table 3 – Sample PSTIB RS-485 interface – Reference signals .13
Table 4 – Generic DLL packet structure .14
Table 5 – Reserved destination address ranges .14
Table 6 – PSTIB Timing specifications .16
Table 7 – Generic DLL datagram structure .18
Table 8 – DLL datagrams .19
Table 9 – Command: Get_Configuration datagram .20
Table 10 – Response: Get_Configuration datagram .20
Table 11 – Response: Get_Configuration datagram variable binding (General) .20
1,2
Table 12 – Response: Get_Configuration datagram variable binding (Power supply) .21
Table 13 – Response: Get_Configuration Datagram Variable Binding (Generator) .24
Table 14 – Command: Get_Power_Supply_Data datagram .25

60728-7-3  IEC:2003(E) – 3 –
Table 15 – Response: Get_Power_Supply_Data datagram.25

Table 16 – Response: Get_Power_Supply_Data Datagram variable binding.25

Table 17 – Command: Power_Supply_Control datagram .27

Table 18 – Command: Get_Generator_Data datagram .28

Table 19 – Response: Get_Generator_Data datagram .28

Table 20 – Response: Get_Generator_Data Datagram variable binding .28

Table 21 – Command: Generator_Control datagram.29

Table 22 – Response: Invalid_Request datagram.29

Table 23 – Response: Request_Processed datagram.29

– 4 – 60728-7-3  IEC:2003(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
CABLE NETWORKS FOR TELEVISION SIGNALS,

SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 7-3: Hybrid Fibre Coax Outside Plant Status Monitoring –

Power Supply to Transponder Interface Bus (PSTIB) specification

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 co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). 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. 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 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 IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 60728-7-3 has been prepared by technical area 5: Cable networks
for television signals, sound signals and interactive services, of IEC technical committee 100:
Audio, video and multimedia systems and equipment.
This standard was submitted to the national committees for voting under the Fast Track
Procedure as the following documents:
CDV Report on voting
100/578/CDV 100/685/RVC
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 2.

60728-7-3  IEC:2003(E) – 5 –
The committee has decided that the contents of this publication will remain unchanged until

2006. At this date, the publication will be

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

• amended.
The following differences exist in some countries:

The Japanese de facto standard (NCTEA S-006) concerning requirements for the HFC
outside plant management, which was published in 1995, has already been available in
Japan. The purpose of this standard is to support the design and implementation of
interoperable management systems for HFC cable networks used in Japan.

– 6 – 60728-7-3  IEC:2003(E)
INTRODUCTION
Standards of the IEC 60728 series deal with cable networks for television signals, sound

signals and interactive services including equipment, systems and installations for

• head-end reception, processing and distribution of television and sound signals and their

associated data signals, and
• processing, interfacing and transmitting all kinds of signals for interactive services

using all applicable transmission media.

All kinds of networks like
• CATV-networks,
• MATV-networks and SMATV-networks,
• individual receiving networks
and all kinds of equipment, systems and installations installed in such networks, are within
this scope.
The extent of this standardization work is from the antennas, special signal source inputs to
the head-end or other interface points to the network up to the system outlet or the terminal
input, where no system outlet exists.
The standardization of any user terminals (i.e. tuners, receivers, decoders, multimedia
terminals, etc.) as well as of any coaxial and optical cables and accessories therefore is
excluded.
60728-7-3  IEC:2003(E) – 7 –
CABLE NETWORKS FOR TELEVISION SIGNALS,

SOUND SIGNALS AND INTERACTIVE SERVICES –

Part 7-3: Hybrid Fibre Coax Outside Plant Status Monitoring –

Power Supply to Transponder Interface Bus (PSTIB) specification

1 Scope
This part of IEC 60728 specifies requirements for the Hybrid Fibre Coax (HFC) Outside Plant
(OSP) Power Supplies (PS). This standard is part of a series developed to support the design
and implementation of interoperable management systems for evolving HFC cable networks.
The purpose of the standards is to support the design and implementation of interoperable
management systems for evolving HFC cable networks. The Power Supply to Transponder
Interface Bus (PSTIB) specification describes the physical (PHY) interface and related
messaging and protocols implemented at the Data Link Layer (DLL), layers 1 and 2
respectively in the 7-layer ISO-OSI reference model, that support communications between
compliant transponders and the managed OSP power supplies and other related power
equipment to which they interface.
This standard describes the PSTIB PHY and DLL layer requirements and protocols that must
be implemented to support reliable communications between all type 2 and type 3 compliant
OSP transponders on the HFC plant and managed OSP power supplies and related hardware.
Any exceptions to compliance with this staneard will be specifically noted as necessary. Refer
to Table 1 for a full definition of the type classifications.
Transponder type classifications referenced within the HMS series of standards are defined in
Table 1.
Table 1 – Transponder type classifications
Type Description Application
• This transponder interfaces with legacy network
equipment through proprietary means.
Refers to legacy transponder
Type 0 equipment which is incapable of
• This transponder could be managed through the same
supporting the specifications
management applications as the other types through
proxies or other means at the head-end
• This transponder interfaces with legacy network
equipment through proprietary means.
Refers to stand-alone transponder
equipment (legacy or new), which can
• Type 1 is a standards-compliant transponder (either
Type 1
be upgraded to support the
manufactured to the standard or upgraded) that
specifications
connects to legacy network equipment via a

proprietary interface
• This transponder interfaces with network equipment
designed to support the electrical and physical
Refers to a stand-alone, compliant
specifications defined in the standards.
Type 2
transponder
• It can be factory or field-installed.
• Its RF connection is independent of the monitored NE
• This transponder interfaces with network equipment
designed to support the electrical specifications
defined in the standards.
• It may or may not support the physical specifications
Refers to a stand-alone or embedded,
Type 3
defined in the standards.
compliant transponder
• It can be factory-installed. It may or may not be field-
installed.
• Its RF connection is through the monitored NE

– 8 – 60728-7-3  IEC:2003(E)
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.

EIA RS-485, Electrical Characteristics of Generators and Receivers for Use in Balanced

Digital Multipoint Systems
3 Terms, definitions and abbreviations

3.1 Terms and definitions
For the purposes of this document, the following definitions apply.
3.2
data link layer (DLL)
layer 2 in the Open System Interconnection (OSI) architecture; the layer that provides
services to transfer data over the physical transmission link between open systems
3.3
network element (NE)
an active element in the outside plant (OSP) that is capable of receiving commands from a
head-end element (HE) in the head-end and, as necessary, providing status information and
alarms back to the HE
3.4
open system interconnection (OSI)
framework of International Organization for Standardization (ISO) standards for
communication between multi-vendor systems that organizes the communication process into
seven different categories that are placed in a layered sequence based on the relationship to
the user. Each layer uses the layer immediately below it and provides services to the layer
above. Layers 7 through 4 deal with end-to-end communication between the message source
and destination, and layers 3 through 1 deal with network functions
3.5
physical (PHY) layer
layer 1 in the Open System Interconnection (OSI) architecture; the layer that provides
services to transmit bits or groups of bits over a transmission link between open systems and
which entails electrical, mechanical and handshaking procedures

3.6
transponder
device that interfaces to outside plant (OSP) NEs and relays status and alarm information to
the HE. It can interface with an active NE via an arrangement of parallel analogue, parallel
digital and serial ports
3.7 Abbreviations
DLL Data Link Layer
EMS Element Management System
Gnd Grund
HE Head-end Element
HFC Hybrid Fibre Coax
ISO International Organization for Standardization

60728-7-3  IEC:2003(E) – 9 –
ISO International Organization for Standardization

LED Light Emitting Diode
MAC Media Access Control
NE Network Element
OSI Open System Interconnection

OSP Outside Plant
PHY Physical
PSTIB Power Supply to Transponder Interface Bus

RF Radio Frequency
Rx Receive
SNMP Simple Network Management Protocol
Tx Transmit
Tx En Transmit Enable
xpndr Transponder
4 Reference architecture forward and return channel specifications
The reference architecture for the series of specifications is illustrated in Figure 1.
Fiber Node
RF Optical RF
RF
Laser
RECEIVER
TRANSMITER Receiver
Splitter
RF Amplifier Chain
Headend
Status
Status
Monitoring
*
Monitoring
Diplexer
Device
Equipment
Optical RF
RF
RF
Laser
Receiver Combiner
RECEIVER
TRANSMITER
B C A
* The diplexer filter may be included as part of the network element to which the
transponder interfaces, or it may be added separately by the network operator.
IEC  2293/03
Figure 1 – Reference architecture diagram
All quantities relating to forward channel transmission or reverse channel reception are
measured at point A in Figure 1. All quantities relating to forward channel reception or reverse
channel transmission are measured at point B for two-port devices and point C for single-port
devices as shown in Figure 1.
5 Power supply to transponder interface bus specification overview
PSTIB specification defines a status monitoring topology intended to replace existing analog,
discrete status monitoring interfaces used today for monitoring power supplies and other
power-related equipment deployed in HFC networks. In this topology, the transponder is
simplified by moving all measurements and sensors to the monitored equipment, i.e. power
supply or other power equipment. The transponder interfaces to the monitored equipment

– 10 – 60728-7-3  IEC:2003(E)

through a single multi-conductor cable. Transponder power is also provided through this

interface. The power supply or other monitored power equipment assumes responsibility for

measuring battery parameters, voltages, and other data associated with the equipment

installation. Status and commands are passed between transponder and monitored equipment

via a serial data interface bus.

The data protocol and command set are simple enough to be implemented in a simple micro-

controller. The communication protocol is open and expandable so that as new requirements

are defined they can be easily added to new revisions of this specification.

5.1 Interface compliance
Transponder and power supply vendors meeting the mechanical and electrical interface
requirements at the PHY layer and the packet and protocol message formats at the DLL layer
that are defined within this specification are said to be interface compliant. A
Get_Configuration command (see 7.4.3) enables the transponder to determine compliance
with a particular revision of this standard for power supplies or other power equipment.
Support for this capability is critical as the PSTIB specification is updated over time and
power supply equipment supporting different revisions of this specification co-exists within the
same network.
5.2 Implementation compliance
Not all vendors will support the complete data set defined throughout this standard. The
Get_Configuration response (see 7.4.3) provides the transponder or EMS with the specific
status data that is and is not supported for each installation.
5.3 Revision control
The command and response data in this standard are synchronized that are used to represent
this data in management systems. To maintain synchronization, a revision control mechanism
must exist. Therefore, any time this standard is revised so that new data items are added to
any command or response, those data items shall be appended to the END of an existing
command or response definition. New command and response sequences may also be
created as needed. No revision shall change the location, definition or function of a previously
defined datum.
6 Power supply to transponder interface bus – Physical layer specification
6.1 Interface requirements
6.1.1 Connector type
The physical connector to support serial communications over the PSTIB between compliant
transponders and managed OSP power supply hardware shall implement the following:
a) RJ-45, eight-wire conductor;
b) appropriate metallic plating for outdoor usage;
c) operating temperature: –40 °C to +70 °C;
d) dual connectors wired in parallel shall be included on the monitored equipment to support
daisy-chaining multiple monitored devices from a single compliant transponder.
6.1.2 Communications interface
The communications interface shall support the EIA RS-485, Electrical Characteristics of
Generators and Receivers for Use in Balanced Digital Multipoint Systems.

60728-7-3  IEC:2003(E) – 11 –

6.1.3 Connector signals
Connector pins shall support signalling as described in Table 2.

Table 2 – RJ-45 Connector pin assignment

Connector Signal
pin number
1, 8 Ground
2, 7 +24 VDC ± 3,6 VDC at 200 mA

(relative tolerance of ±15 %)
3, 6 RS-485 (+)
4, 5 RS-485 (–)
6.1.4 Transponder power
Powering of transponders from PSTIB interface compliant power supplies shall support the
following attributes:
a) the transponder is powered only from the power supply. The transponder shall not connect
directly to the system batteries;
b) the power supply shall implement appropriate isolation and system grounding so that the
communication interface and transponder power remains functional under the operating
conditions defined herein;
c) the transponder shall be bonded to chassis ground directly and/or through the system
coaxial cable sheath;
d) optionally, transponder power may be bonded to chassis ground at the power supply
interface. The power supply vendor shall determine this;
e) the power supply shall implement appropriate over-current and short-circuit protection of
transponder power so that the communication interface and transponder power remain
functional under the operating conditions defined herein;
f) up to eight (8) power supplies may be connected in parallel using the RS-485 interface.
6.1.5 Line balance
6.1.5.1 Monitored equipment
Line balance for monitored equipment shall be implemented as follows:
a) RS-485 (+) to a DC voltage of +5 V through a resistor (jumper/switch removable);

b) RS-485 (–) to ground through a resistor (jumper/switch removable);
c) RS-485 (+) tied to RS-485 (–) through a resistor (jumper/switch removable);
d) monitored equipment shall include jumpers to select or bypass resistors to an open state.
Jumper or switch-selectable terminating resistors enable on-site configuration of individual
installations. Transponders shall include line balance resistors only. Refer to Figure 2.
6.1.5.2 Transponder
Line balance for transponders shall be implemented as follows:
– RS-485 (+) tied to RS-485 (–) through a required resistor.
NOTE Values for each resistor and the decision to include or exclude specific bias resistors as a default should
be determined by individual vendors.

– 12 – 60728-7-3  IEC:2003(E)

6.1.6 Cable length
A maximum cable length of 1 219,2 m (4 000 ft) (@100 kbit/s) properly terminated wire

segment.
6.1.7 Data encoding
Non-return to zero (NRZ), asynchronous, 1 start bit, 8 data bits (ordering: bit 1,2 … 8), 1 stop
bit. All integers are transmitted most significant byte first. Any exceptions to this rule will be

specifically noted in this standard as necessary.

6.1.8 Bit rate
The bit rate supported shall be 9 600 Bd.
6.1.9 Duplex
This interface shall support half duplex operation. Multi-drop characteristics of RS-485 enable
up to 32 drops per segment without signal repeaters.
6.1.10 Method of communications
All communication is transponder-initiated. One monitored device response per query.
6.1.11 Indicators
An LED or other visual device installed at the monitored equipment shall indicate
communication has been established with a transponder over the PSTIB interface.
6.2 Interface diagram
The diagram in Figure 2 illustrates a sample RS-485 interface implementation to support
PSTIB communications. This diagram should not be interpreted as a design requirement. It is
only included to help clarify line bias and termination resistor placement. Table 3 describes
the various signals that have been referenced in this diagram.

60728-7-3  IEC:2003(E) – 13 –

MONITORED
TRANSPONDER
EQUIPMENT
+Vxpndr +Vxpndr +5xpndr
+5
+5
* Option V c c
J1 J2
V c c
Rx
1 1 R
Rx
R 2 2
3 3
120 2
4 4
Tx En
2 3
Required
5 5
Tx En 3
* Option
6 6
7 7
Tx
7 4
8 8
D
Tx
D
G n d
G n d 750
5 * Option
IEC  2304/03
Figure 2 – Sample PSTIB RS-485 interface
Table 3 – Sample PSTIB RS-485 interface – Reference signals
Signal notation Description
(Figure 2)
+5 Monitored equipment voltage
+Vxpndr Voltage supplied from the monitored equipment to the transponder as defined per this
specification
+5xpndr Transponder operating voltage derived at the transponder from +Vxpndr
*Option Indicates resistors that can be included or removed from circuit via user configurable
jumper or switch
Required Indicates resistor is required per this specification
J1, J2 The RJ-45 connectors used to interface transponders to monitored equipment. Pin
numbers show currently defined interface signals per this specification
Rx, Tx, Tx En Transmit, Receive and Transmit Enable. Illustrates possible connections to an RS-485
interface IC.
GROUND The transponder should be chassis grounded. The monitored equipment may be tied to
chassis ground directly, i.e. at the monitored equipment status interface, or through the
interface ground (J1 pins 1,8). This should be at the discretion of the monitored
equipment vendor. The monitored equipment and status interface should function
correctly with whatever grounding method is selected.
7 Power supply to transponder interface bus – Data link layer specification
7.1 DLL packet structure
DLL packets consist of the following: start field, destination address field, source address
field, identification field, a variable-length datagram field, end field and two-byte checksum
field. DLL packet structure is illustrated in Figure 3.

– 14 – 60728-7-3  IEC:2003(E)

Start End
Start Destination Source Identification Datagram End Checksum
Address Address
Figure 3 – DLL packet structure

All DLL packets shall have the general format as described in Table 4.

Table 4 – Generic DLL packet structure

Field name Length (bits) Subclause

Start 16 7.1.1
Destination Address 8 7.1.2
Source Address 8 7.1.3
Identification 8 7.1.4
Datagram 32 to N 7.1.5
End 16 7.1.6
Checksum 16 7.1.7
7.1.1 Start
The Start field consists of two octets (bytes). This is the start sequence of all communication
packets. This field shall consist of DLE (0x10) followed by STX (0x02).
7.1.2 Destination Address
The Destination Address field consists of a single octet and it uniquely identifies the device
receiving the packet. Its value is between 0x00 and 0xFF (0-255 decimal). Table 5 includes
the ranges of addresses that are currently defined as part of this standard.
Table 5 – Reserved destination address ranges
Range Range Reserved for
(decimal) (hexadecimal)
0 0x00 Transponders
1 - 8 0x01 - 0x08 Power supplies
9 - 31 0x09 - 0x1F Reserved for vendor specific equipment *
32 - 255 0x20 - 0xFF Specified use

* NOTE It is recommended that 0x10 is not used as a device address to avoid
additional DLE sequences (defined later in 7.2).
7.1.3 Source Address
The Source Address field consists of a single octet and it uniquely identifies the device
sending the packet. Its format is the same as that of the Destination Address field.
7.1.4 Identification
The Identification field consists of a single octet. It is used to help identify the packet and
match send-receive packet sequences. The contents of this field are defined by the device
initiating communications,i.e. as currently defined, this will always be the transponder. The
receiving device will repeat the Identification in the corresponding field of its response packet.

60728-7-3  IEC:2003(E) – 15 –

7.1.5 Datagram
The Datagram field consists of a minimum of four octets. It contains the commands, command

responses and data delivered to/from the higher layer protocols. Various datagram types and

their structure are defined later in 7.4.

7.1.6 End
The End field consists of two octets. This is the end sequence of all communication packets.

This field shall consist of DLE (0x10) followed by ETX (0x03).

7.1.7 Checksum
The Checksum field consists of two octets. This is the 16-bit (modulo 0x10000) sum of all
bytes in the packet excluding the Start, End, and Checksum fields and any stuffed DLEs.
7.2 DLE sequence
Data Link Escape (DLE) sequence stuffing assures that both START (DLE, STX) and END
(DLE, ETX) sequences will never be duplicated within the body of a packet. This technique is
used to facilitate identifying the start and end of variable-length packets. Within the packet, if
an octet is encountered having the value DLE, i.e. hexadecimal 0x10 or decimal 16, a second
DLE is inserted into the data stream when the packet is transmitted. The following example
illustrates this technique (data represented in hexadecimal format):
Original packet: 10 02 30 20 63 10 03 00 10 03 00 C6
DLE stuffed: 10 02 30 20 63 10 10 03 00 10 03 00 C6
NOTE The above example illustrates only the DLE stuffing technique. Specific Command and Response
information is not intended to represent actual data.
Notice the 6th and 7th octets in the original packet in the above example. These could
mistakenly be interpreted as the end-of-packet sequence. The DLE-stuffed packet includes an
additional DLE inserted in the sequence. The receiving device will detect the DLE
combination, discard the inserted DLE and ignore the DLE ETX code embedded within the
packet.
The following rules shall apply to DLE stuffing:
a) DLE stuffing is applied to the entire packet including the checksum. Therefore, an
additional DLE character will be added for each checksum byte sent as 0x10 (DLE);
b) the start packet sequence (DLE, STX) and end packet sequence (DLE, ETX) are not DLE
stuffed;
c) the value in any DLL datagram “Size of Data” field (see 7.4.1.2) does not include any
stuffed DLE characters;
d) stuffed DLE characters are not included in packet checksum calculations.
7.3 Interface timing
7.3.1 Message synchronization and interaction
Transponders and monitored equipment must conform to the following:
a) transponders initiate all communications. Monitored equipment, for example power
supplies, shall only respond to packets addressed to them;
b) transponders powered directly via the RJ-45 physical connector from a PSTIB interface
compliant power supply shall wait at least 15 s after power up and initialization before
attempting to discover what power supplies they are connected to over the same PSTIB
interface. A power supply shall be fully initialized and capable of responding to any data

– 16 – 60728-7-3  IEC:2003(E)

message as defined in this standard within 15 s after it has enabled power over the PSTIB

interface to the transponder. The power supply shall not respond, nor respond with

incorrect data, if it is interrogated before this time elapses;

c) transponders shall assign each data message a unique identification (refer to 7.1.4). The

responding device shall repeat this identifier in the identification field of the response

packet. The transponder shall verify the message identifier ensuring command/response

synchronization;
d) transponders should include a mechanism to re-request or retry communications when

either a corrupt response or no response is received from the monitored equipment. Since

communication errors will occur in any system, transponders shall retry communications a

minimum of three (3) times before reporting loss of communications with the monitored

equipment to the EMS. If loss of communications occurs, the transponder shall attempt to
re-establish communications with the monitored equipment at regular intervals. All
communications shall conform to the timing requirements defined in this standard. See
7.3.2.
7.3.2 Transmission timing requirements
Figure 4 illustrates the data and timing diagram for transmissions over the PSTIB. Table 6
describes all relevant timing parameters and allowed minimum and maximum values.
t5
PRIMARY
TRANSPONDER
DATA Tx
t1 t2
t3
POWER SUPPLY
RESPONSE
t3
t4
t1 t2
SECONDARY DEVICE
DATA Tx
(e.g., Laptop)
IEC  2305/03
Figure 4 – PSTIB data and timing diagram
Table 6 – PSTIB timing specifications
Identifier Characteristic Minimum value Maximum value
t1 PRIMARY or SECONDARY device packet duration - 30 ms
t2 Delay – PRIMARY or SECONDARY device 1 ms 30 ms
message complete to power supply start response
t3 Power supply packet duration (chatter detection) - 300 ms
t4 PRIMARY device packet start to SECONDARY 390 ms 510 ms
device packet start
t5 PRIMARY device poll cycle period 900 ms 3 s
The diagram in Figure 4 and Table 6 make provision for more than one device initiating
communications over the PSTIB. If a device initiating communications is a transponder, i.e. a
device with address 0x00, it is referred to as a PRIMARY device. If the device initiating
communications is one with a non-zero address, i.e. a laptop PC or another transponder with
non-zero address, it is referred to as a SECONDARY device.
7.3.2.1 Requirements for PRIMARY and SECONDARY devices
It may be desirable for on-site technicians to access power supply and generator system
status using a laptop PC. This subclause defines the timing requirements for a laptop-based
PC application program to send and receive status to and from the monitored equipment via
the RS-485 interface without disrupting communications to or from the transponder. The
following rules govern this mode of operation:

60728-7-3  IEC:2003(E) – 17 –

a) transponders and monitored equipment shall anticipate that there may be a SECONDARY

device, for example a laptop PC, connected to the RS-485 bus;

b) the PRIMARY device, also called the transponder, shall be set to address zero. The

SECONDARY device shall be set to any unused address;

c) in order to establish timing synchronization with the SECONDARY device, the transponder
(with address 0x00) shall regularly transmit packets at a period herein defined by the

timing requirements for the PRIMARY transponder;

d) the SECONDARY device shall determine if there is a zero-addressed PRIMARY device on

the bus. It will do this by listening on the bus for a zero-addressed transponder;

e) if the SECONDARY device listens on the bus for a time equal to the maximum value of a

PRIMARY device poll cycle period, i.e. 3 s, and does not hear a zero-addressed
transponder, it shall proceed to operate as if it is the PRIMARY transponder;
f) if a SECONDARY device is acting as PRIMARY, and if 60 s or more have passed since
the SECONDARY device has listened for a zero-addressed transponder, the
SECONDARY device shall not transmit until it has again determined if there is a zero-
addressed transponder on the bus;
g) a PRIMARY transponder shall be able to tolerate continuous bus collisions for up to 60 s
without crashing and without deviating from any other requirements assigned to a
PRIMARY transponder, i.e. it needs to continue transmitting at the defined period even
though it may not be receiving any responses;
h) if a SECONDARY device; i.e. a device with non-zero address, is acting as PRIMARY and
determines that a zero-addressed transponder has been placed on the bus, the non-zero
addressed device shall cease acting like a PRIMARY transponder and immediately start
acting like a SECONDARY device;
i) when a PRIMARY transponder is on the bus, a SECONDARY device shall start any
transmission no less than “t4 minimum” after it has seen the PRIMARY transponder start a
transmission;
j) when a PRIMARY transponder is on the bus, a SECONDARY device shall start its
transmission no more than “t4 maximum” after it has seen the PRIMARY transponder start
a transmission;
k) transponders which are permanently installed in a system shall be configured with
address 0x00 and operate as a PRIMARY transponder;
l) for all responses, PRIMARY and SECONDARY devices shall confirm that the destination
address is their own address, and process only those packets addressed to them; i.e.
devices must not assume that all traffic on the bus is either from or to them;
m) monitored equipment shall be able to service requests from multiple devices. The
monitored equipment can be assured by these rules that messages will never be
interleaved; i.e. while responding to one device, they will never receive a request from a
second device.
7.4 DLL datagrams
7.4.1 Structure
The Datagram field is defined as part of the DLL packet structure (see Figure 3). Datagrams
contain commands, command responses and associated data. DLL datagram structure is
illustrated in Figure 5.
COMMAND/ Size of data Variable binding
RESPONSE
IEC  2306/03
Figure 5 – DLL datagram structure
All DLL datagrams must have the general format as described in Table 7.

– 18 – 60728-7-3  IEC:2003(E)

Table 7 – Generic DLL datagram structure

Field name Length (bits) Subclause

COMMAND/RESPONSE 16 7.4.1.1
Size of data 16 7.4.1.2
Variable binding 0 to N 7.4.1.3

7.4.1.1 Command/Response
The Command/Response field consists of two octets (bytes). This field defines what action is

to be performed. The Command/Response field is always present. Valid commands and
responses are defined later in 7.4.3. This two-octet field is transmitted most significant byte
first.
7.4.1.2 Size of Data
The Size of Data field consists of two octets. This value defines the size (in bytes) of the
Variable Binding field. This Size of Data field is always present. If no data is associated with
the command, the size will be 0x0000. This two-octet field is transmitted most significant byte
first.
7.4.1.3 Variable Binding
This variable field contains data. The data length and content are specific to a particular
command/response. This field is not always present. If no data are present, the Size of Data
field is set to 0x0000.
7.4.2 Resolution versus accuracy
The Variable Binding field in a DLL datagram contains digital representations of analogue
values. The resolution of each analogue value is listed in the tables describing associated
variable bindings for each DLL datagram type in 7.4.3. Resolution does not imply accuracy.
Vendors should disclose accuracy of status data for equipment in compliance with this
specification. Any scaled analogue representation from a Get_Power_Supply_Data response
(see 7.4.3.4) that reaches the minimum or maximum range defined for that value, i.e. 0 or
255, shall report the maximum (or minimum) value and not wrap around.
7.4.3 DLL datagram types
Valid datagram types defined in this standard are listed in Table 8.

60728-7-3  IEC:2003(E) – 19 –

Table 8 – DLL datagrams
Datagram name Encoding Size of data (bytes) Subclause

Get_Configuration (Command) 0x3030 0 7.4.3.1

Get_Configuration (Response) 0x3130 Device type dependent 7.4.3.2

Get_Power_Supply_Data (Command) 0x3031 0 7.4.3.3

Get_Power_Supply_Data (Response) 0x3131 33 7.4.3.4

Power_Supply_Control (Command) 0x3232 1 7.4.3.5

Get_Generator_Data (Command) 0x3033 0 7.4.3.6

Get_Generator_Data (Response) 0x3133 10 7.4.3.7
Generator_Control (Command) 0x3234 1 7.4.3.8
Invalid_Request (Response) 0x34nn 1 7.4.3.9
Request_Processed (Response) 0x35nn 0 7.4.3.10
nn is the second byt
...