Symphony BRC-100 User manual

Instruction
Harmony Series
Bridge Controller and Processor Bus Adapter
BRC-100 and PBA-100

WBPEEUI230017B1
Preface
The BRC-100 Harmony Bridge Controller is a high-perfor-
mance, high-capacity process controller. It is a rack controller
designed to interface with both Harmony I/O blocks and Har-
mony rack I/O in the Symphony Enterprise Management and
Control System. The Harmony bridge controller is fully com-
patible with the INFI 90®OPEN system in functionality, com-
munication and packaging. The Harmony bridge controller
collects process I/O, performs control algorithms and outputs
control signals to process level devices. It also imports and
exports process data of other controllers and system nodes,
and accepts control commands from operators and computers
connected to the network.
This instruction provides information about how the Harmony
bridge controller works, and how to install, configure, operate
and troubleshoot the module.
The Harmony bridge controller is designed for redundancy.
This can be achieved while remaining connected to the Hnet, or
without, using an optional BRC redundancy kit.

WBPEEUI230017B1
List of Effective Pages
NOTE: Changed text or tables are indicated by a vertical bar adjacent to the changed area. Changed fig-
ures are indicated by a vertical bar next to the figure caption. The date appears beside the page number.
Total number of pages in this instruction is 99, consisting of the following:
Page No. Change Date
Preface 04 December 2000
List of Effective Pages 04 December 2000
iii through x 04 December 2000
1-1 through 1-8 04 December 2000
2-1 through 2-8 04 December 2000
3-1 through 3-19 04 December 2000
4-1 through 4-5 04 December 2000
5-1 through 5-23 04 December 2000
6-1 through 6-4 04 December 2000
7-1 through 7-3 Original
8-1 04 December 2000
A-1 through A-8 Original
B-1 through B-7 04 December 2000
Index-1 through Index-3 04 December 2000
When an update is received, insert the latest changed pages and dispose of the superseded
pages.

WBPEEUI230017B1 iii
Table of Contents
Section 1 Introduction ..................................................................................................1-1
Overview .................................................................................................................. 1-1
Intended User .......................................................................................................... 1-2
Hardware Description .............................................................................................. 1-2
Faceplate ............................................................................................................. 1-3
Circuit Board ....................................................................................................... 1-3
Hardware Application............................................................................................... 1-3
Features .................................................................................................................. 1-3
Instruction Content.................................................................................................. 1-4
How to Use this Instruction ...................................................................................... 1-4
Glossary of Terms and Abbreviations........................................................................ 1-5
Reference Documents............................................................................................... 1-6
Related Nomenclatures ............................................................................................ 1-6
Specifications........................................................................................................... 1-6
Section 2 Description and Operation .........................................................................2-1
Introduction............................................................................................................. 2-1
Operation................................................................................................................. 2-1
Circuitry .................................................................................................................. 2-2
Microprocessor..................................................................................................... 2-2
Clock and Real-Time Clock ................................................................................... 2-2
Memory................................................................................................................ 2-2
Direct Memory Access .......................................................................................... 2-3
Controlway........................................................................................................... 2-4
Redundancy Link ................................................................................................. 2-4
Hnet Communication ........................................................................................... 2-5
I/O Expander Bus ................................................................................................ 2-5
I/O Section .......................................................................................................... 2-6
Serial Channels.................................................................................................... 2-6
Station Link ......................................................................................................... 2-6
Power................................................................................................................... 2-7
Section 3 Installation ....................................................................................................3-1
Introduction............................................................................................................. 3-1
Special Handling ...................................................................................................... 3-2
Unpacking and Inspection........................................................................................ 3-2
Dipswitches and Jumpers ........................................................................................ 3-3
Dipswitch SW5 - Module Address ......................................................................... 3-4
Dipswitch SW2 - Normal Operating Options.......................................................... 3-5
Dipswitch SW2 - Special Operations ..................................................................... 3-5
Dipswitch SW3 - Module Options ......................................................................... 3-8

iv WBPEEUI230017B1
Table of Contents (continued)
Section 3 Installation (continued) ..........................................................................................
Dipswitch SW4 - Module Options ..........................................................................3-8
Jumpers ...............................................................................................................3-8
Module Mounting Unit Preparation ...........................................................................3-9
Module Slot Assignments ......................................................................................3-9
Dipshunts ..........................................................................................................3-10
Controlway Cable................................................................................................3-10
PBA Board Installation........................................................................................3-11
Mounting Bracket ...........................................................................................3-11
Cable and Terminator .....................................................................................3-12
Mounting ........................................................................................................3-13
BRC Redundancy Kit Installation ........................................................................3-16
Module Installation.................................................................................................3-18
Pre-Installation Check ........................................................................................3-18
Installation .........................................................................................................3-19
Section 4 Operating Procedures .................................................................................4-1
Introduction .............................................................................................................4-1
Startup.....................................................................................................................4-1
Module LEDs............................................................................................................4-2
Front Panel LEDs..................................................................................................4-2
Red/Green Status LED .........................................................................................4-3
Stop/Reset Switch ....................................................................................................4-3
Modes of Operation...................................................................................................4-4
Section 5 Troubleshooting ..........................................................................................5-1
Introduction .............................................................................................................5-1
Error Codes ..............................................................................................................5-1
Flowcharts ...............................................................................................................5-5
Diagnostics ..............................................................................................................5-5
Overview...............................................................................................................5-5
Diagnostic Test Selection ......................................................................................5-8
LED Display .......................................................................................................5-11
Module Status Summary ........................................................................................5-12
Card Edge Connectors ............................................................................................5-17
Section 6 Maintenance .................................................................................................6-1
Introduction .............................................................................................................6-1
Preventive Maintenance Schedule .............................................................................6-1
Equipment and Tools Required .................................................................................6-1
Preventive Maintenance Procedures ..........................................................................6-2

WBPEEUI230017B1 v
Table of Contents (continued)
Section 6 Maintenance (continued) .......................................................................................
Printed Circuit Board Cleaning ............................................................................. 6-2
General Cleaning and Washing ......................................................................... 6-3
Edge Connector Cleaning.................................................................................. 6-3
Checking Connections.......................................................................................... 6-4
Section 7 Repair and Replacement .............................................................................7-1
Introduction............................................................................................................. 7-1
Module Replacement ................................................................................................ 7-1
PBA Board Replacement........................................................................................... 7-2
Section 8 Replacement and Spare Parts ....................................................................8-1
Parts........................................................................................................................ 8-1
Appendix A Online Configuration .............................................................................. A-1
Introduction............................................................................................................. A-1
Setup....................................................................................................................... A-1
Operation................................................................................................................. A-2
Backup Cycle ....................................................................................................... A-3
Primary Cycle....................................................................................................... A-6
Appendix B NTMP01 Termination Unit ...................................................................... B-1
Description ..............................................................................................................B-1
List of Figures
No. Title Page
1-1. Harmony Bridge Controller Architecture.................................................... 1-2
2-1. Functional Block Diagram......................................................................... 2-3
3-1. BRC Module Layout ................................................................................. 3-3
3-2. Controlway Cable Installation ................................................................. 3-11
3-3. PBA Installation ...................................................................................... 3-14
3-4. PBA Connector Identification................................................................... 3-15
3-5. BRC Redundancy Kit Installation ............................................................ 3-17
3-6. Hood Connector Assembly Connector Identification ................................. 3-18
4-1. Front Panel ............................................................................................... 4-2

vi WBPEEUI230017B1
List of Figures (continued)
No. Title Page
5-1. Troubleshooting Flowchart (Serial Port) .....................................................5-6
5-2. Troubleshooting Flowchart (Status LED)....................................................5-7
5-3. LEDs - Pass/Fail .....................................................................................5-12
A-1. Backup Cycle ........................................................................................... A-6
A-2. Primary Cycle ........................................................................................... A-8
B-1. DTE Jumper Configuration (NTMP01) ....................................................... B-2
B-2. DCE Jumper Configuration (NTMP01)....................................................... B-2
B-3. Nonhandshake Jumper Configuration (NTMP01)....................................... B-3
B-4. Loopback Jumper Configuration (NTMP01) ............................................... B-3
B-5. Jumpers J3 through J10 Configuration (NTMP01) .................................... B-4
B-6. NTMP01 Board Layout.............................................................................. B-5
B-7. NTMP01 Cable Connections (Redundant BRC Modules/PBA Boards) ........ B-6
B-8. Cable Connections (Redundant BRC Modules Using BRC Redundancy Kit) B-7
List of Tables
No. Title Page
1-1. Glossary of Terms and Abbreviations .........................................................1-5
1-2. Reference Documents ................................................................................1-6
1-3. Related Nomenclatures ..............................................................................1-6
1-4. Specifications ............................................................................................1-7
3-1. Dipswitch SW5 Settings (Operation)...........................................................3-4
3-2. Dipswitch SW5 Settings (Address)..............................................................3-5
3-3. Dipswitch SW2 Settings (Operating Options)..............................................3-6
3-4. Dipswitch SW2 Settings (Special Operations) .............................................3-7
3-5. Dipswitch SW4 Settings (Module Options)..................................................3-8
3-6. Jumpers Settings (J1 through J4) ..............................................................3-9
5-1. Error Codes ...............................................................................................5-1
5-2. Status LED and Other Conditions..............................................................5-4
5-3. DSO and BRC Setup for I/O Expander Bus Test ........................................5-8
5-4. Diagnostic Dipswitch Settings....................................................................5-8
5-5. Diagnostic Tests ........................................................................................5-9
5-6. Status Report ..........................................................................................5-13
5-7. Status Report Field Descriptions..............................................................5-13
5-8. P1 Pin Assignments (BRC) .......................................................................5-17
5-9. P2 Pin Assignments (BRC) .......................................................................5-18
5-10. P3 Pin Assignments (BRC)1,2 ..................................................................5-18
5-11. P4 Pin Assignments (BRC) .......................................................................5-19
5-12. P1 Pin Assignments (PBA) ........................................................................5-19

WBPEEUI230017B1 vii
List of Tables (continued)
No. Title Page
5-13. P3 Pin Assignments (PBA) ....................................................................... 5-20
5-14. P4 Pin Assignments (PBA) ....................................................................... 5-20
5-15. P5 Pin Assignments (PBA) ....................................................................... 5-21
5-16. P5 Pin Assignments (Hood Connection Assembly) .................................... 5-22
6-1. Preventive Maintenance Schedule.............................................................. 6-2
8-1. Miscellaneous Nomenclatures ................................................................... 8-1
8-2. Cable Nomenclatures ................................................................................ 8-1
8-3. Miscellaneous Parts .................................................................................. 8-1
A-1. Legend of Symbols .................................................................................... A-3
A-2. Backup Cycle ............................................................................................ A-3
A-3. Primary Cycle............................................................................................ A-7

viii WBPEEUI230017B1
Safety Summary
GENERAL
WARNINGS
Equipment Environment
All components, whether in transportation, operation or storage,
must be in a noncorrosive environment.
Electrical Shock Hazard During Maintenance
Disconnect power or take precautions to insure that contact with
energized parts is avoided when servicing.
Special Handling
This module uses electrostatic sensitive devices.
SPECIFIC
WARNINGS
Disconnect power before installing dipshunts on the module mount-
ing unit backplane. Failure to do so will result in contact with cabinet
areas that could cause severe or fatal shock. (p. 3-9)
Disconnect power before installing the processor bus adapter
mounting bracket on the module mounting unit backplane. Failure to
do so will result in contact with cabinet areas that could cause
severe or fatal shock. (p. 3-11)
Wear eye protection whenever working with cleaning solvents.
When removing solvents from printed circuit boards using com-
pressed air, injury to the eyes could result from splashing solvent as
it is removed from the printed circuit board. (p. 6-1)
SPECIFIC
CAUTIONS
Never operate the BRC module with the machine fault timer circuit
disabled (jumper pins connected). Unpredictable module outputs
and configuration corruption may result. The unpredictable module
outputs may damage control equipment connected to the BRC
module.
To avoid potential module damage, evaluate your system for com-
patibility prior to module installation. This module uses connections
to the module mounting unit backplane that served other functions
in early Network 90 systems. (p. 3-16)

WBPEEUI230017B1 ix
Support Services
ABB will provide assistance in the operation and repair of its
products. Requests for sales or application services should be
made to your nearest sales or service office. ABB can also pro-
vide installation, repair and maintenance contract services.
When ordering parts, use nomenclature or part numbers and
part descriptions from equipment manuals. Parts without a
description must be ordered from the nearest sales or service
office. Recommended spare parts lists, including prices are
available though the nearest sales or service office.
ABB has modern training facilities available for training your
personnel. On-site training is also available. Contact your
nearest ABB sales office for specific information and schedul-
ing.
Additional copies of this instruction, or other instructions, can
be obtained from the nearest ABB sales office at a reasonable
charge.

xWBPEEUI230017B1
Trademarks and Registrations
Registrations and trademarks used in this document include:
® INFI 90 Registered trademark of ABB Process Automation.
® INFI-NET Registered trademark of ABB Process Automation.
® Network 90 Registered trademark of ABB Process Automation.

WBPEEUI230017B1 1 - 1
Section 1
Introduction
Overview
The BRC-100 Harmony Bridge Controller is a high-perfor-
mance, high-capacity process controller. It is a rack controller
designed to interface with both Harmony I/O blocks and Har-
mony rack I/O in the Symphony Enterprise Management and
Control System. The Harmony bridge controller (BRC) is fully
compatible with the INFI 90 OPEN system in functionality,
communication, and packaging.
The Harmony bridge controller is a stand-alone controller that
can handle specific control and information processing appli-
cations in addition to multiple-loop analog, sequential, and
batch control. It has the power to execute demanding process
control applications that are data intensive, program intensive
or both. The Harmony bridge controller supports multiple con-
trol languages which include function codes, C, Basic,
Batch 90, and Ladder.
The Symphony system uses a variety of analog, control, and
digital I/O devices to interface with the process. Control input/
output is available from I/O blocks using the Harmony com-
munication network (Hnet) or from Harmony rack I/O modules
using the I/O expander bus.
For added reliability, the BRC module has circuitry that sup-
ports redundancy. A backup BRC module waits in a standby
mode while the primary module executes. If the primary goes
offline for any reason, there is a bumpless transfer of control to
the backup module. A processor bus adapter (PBA) board is
required to support redundant BRC modules and redundant
Hnet buses. When no Hnet and termination unit connection is
needed, a BRC redundancy kit may be used to support redun-
dant BRC modules.
IISAC01 Analog Control Stations can connect directly to the
BRC module via a PBA board and termination unit. The BRC
module also supports IISAC01 stations that are connected to a
Harmony control I/O block (CIO-100/110) on the Hnet bus or
a Harmony control I/O module (IMCIS12, IMQRS12) on the I/
O expander bus. The BRC module supports up to 128 SAC sta-

1 - 2 WBPEEUI230017B1
Intended User
tions communication at a 40-kbaud rate. Figure 1-1 shows the
Harmony bridge controller architecture.
Intended User
Personnel installing, operating or maintaining the BRC module
should read this instruction before performing any installa-
tion, operation, or maintenance procedures. Installation
requires an engineer or technician with experience handling
electronic circuitry. Formal training in Symphony system con-
figuration (especially function codes) is helpful when configur-
ing the BRC module.
Figure 1-1. Harmony Bridge Controller Architecture
HARMONY RACK
COMMUNICATION
MODULES
HARMONY
BRIDGE
CONTROLLER
HARMONY RACK
I/O M O D U LE S
REPEATER
MOUNTING
UN IT (R MU)
RMU
HARMONY
I/O BLOCKS
HARMONY
I/O BLOCKS
CNET
HNET
HNET
HNET
T02467A
CONTROLWAY
I/O EXPANDER BU S
PROCESS I/OPROCESS I/O PROCESS I/O
REMOTE LOCATION

Hardware Description
WBPEEUI230017B1 1 - 3
Hardware Description
The Harmony bridge controller consists of a circuit board and
a faceplate.
Faceplate
The BRC faceplate measures 35.56-millimeters wide by
177.80-millimeters high (1.4-inches wide by 7.0-inches high).
Two latching screws, one at the top, the other at the bottom,
lock the module assembly in a module mounting unit (MMU). A
transparent window on the faceplate enables viewing the 16
CPU LEDs and the status LED. These LEDs display operating
information. A small hole directly below the window provides
access to the combination stop/reset pushbutton. Besides
locking the module in place, the faceplate also protects the cir-
cuit components and promotes proper air flow within the
enclosure.
Circuit Board
The circuit board features state-of-the-art surface mount tech-
nology. On the board are nonvolatile random access memory
(NVRAM), static random access memory (SRAM), flash memory
(ROM), a microprocessor running at 32 megahertz, direct
memory access (DMA) circuits, ABB Process Automation cus-
tom bus circuits, and various support circuitry. The board
attaches to the faceplate with two screws. The module assem-
bly occupies one slot in a module mounting unit.
A processor bus adapter board is required for connection to the
Harmony I/O subsystem via Hnet. It also connects to a termi-
nation unit for two auxiliary serial I/O ports and IISAC01 sta-
tions. Redundant BRC modules and Hnet buses connect
through redundant PBA boards.
Hardware Application
Because of the superior performance of the BRC module, appli-
cations that formerly required an external mainframe or mini-
computer can now be handled in the Harmony control unit.
The large memory space and on-board communication ports of
the BRC module enable it to meet the sophisticated control

1 - 4 WBPEEUI230017B1
Features
application requirements of supervisory control, optimization
routines, performance assessment, and process modeling.
Features
The Harmony bridge controller retains all of the features of the
INFI 90 OPEN multifunction processor modules. Additional
features of the Harmony bridge controller include:
•Simultaneous Hnet bus and I/O expander bus communi-
cation supports both Harmony I/O blocks and Harmony
rack I/O modules.
•Redundant Hnet bus.
•Online Hnet communication bus diagnostics and fault
isolation.
•Automatic downloading of Harmony I/O block
configurations.
•NVRAM battery power monitoring.
•Status output alarm monitoring.
•Two megabytes of on-board SRAM memory.
•Compatible with existing INFI 90 OPEN systems.
Instruction Content
This instruction consists of the following sections:
Introduction Provides an overview of the module, a description of the hard-
ware, a glossary of unique terms, and a table of physical, elec-
trical and environmental specifications.
Description and
Operation
Uses block diagrams to explain the function of the key circuits.
Installation Explains the handling, inspection, hardware configuration,
and installation aspects of the module.
Operating Procedures Discusses the front panel indicators and controls, and every-
day operation.
Troubleshooting Features detailed flowcharts and tables that enable quick diag-
nosis of error conditions and provides corrective actions.

How to Use this Instruction
WBPEEUI230017B1 1 - 5
Maintenance Covers scheduled module maintenance.
Repair and
Replacement
Describes how to repair and replace the module.
Replacement and Spare
Parts
Provides a list of part numbers and nomenclatures.
Appendices Provide quick reference information for NTMP01 hardware
configuration and step-by-step instructions for performing
online configuration.
How to Use this Instruction
Read this instruction in sequence. To get the best use out of
this instruction, read it from cover to cover, then go back to
specific sections as required. ABB strongly advises against
putting the module into operation until the installation section
has been read and performed.
1. Read and perform all steps in the installation section.
2. Thoroughly read the operating procedures section before
applying power to the module.
3. Refer to the troubleshooting section if a problem occurs.
This section will help to diagnose and correct a problem.
4. Go to the repair and replacement section for replacement
part numbers and nomenclatures, and for instructions on how
to replace the module.
Glossary of Terms and Abbreviations
Table 1-1 contains those terms and abbreviations that are
unique to ABB or have a definition that is different from stan-
dard industry usage.
Table 1-1. Glossary of Terms and Abbreviations
Term Definition
Controlway High speed, redundant, peer-to-peer communication link. Used to transfer infor-
mation between intelligent modules within a Harmony control unit.
Hnet Communications path between Harmony controller and I/O blocks.
Executive block Fixed function block that determines overall module operating characteristics.

1 - 6 WBPEEUI230017B1
Reference Documents
Reference Documents
Table 1-2 contains a list of documents referenced in this
instruction that provide information on BRC firmware and
related hardware.
Function block The occurrence of a function code at a block address of a module.
Function code An algorithm which manipulates specific functions. These functions are linked
together to form the control strategy.
I/O block Generic name for a processor based Harmony input/output device: AIN-120,
AOT-150, CIO-100, DIO-400, etc.; comprised of an I/O module and a base.
I/O module Houses the I/O block circuitry; part of I/O block.
I/O expander
bus
Parallel communication bus between the Harmony rack controller and Harmony
rack I/O modules.
MFT Machine fault timer. Reset by the processor during normal operation. If not reset
regularly, the MFT times out and the module stops.
MMU Module mounting unit. A card cage that provides electrical and communication
support for Harmony rack modules.
PBA Processor bus adapter.
Termination unit Provides input/output connection between plant equipment and the Harmony
rack modules.
Table 1-1. Glossary of Terms and Abbreviations (continued)
Term Definition
Table 1-2. Reference Documents
Number Title
WBPEEUI200502?? Module Mounting Unit (IEMMU11, IEMMU12,
IEMMU21, IEMMU22)
WBPEEUI210504?? Function Code Application Manual, Symphony
WBPEEUI230022?? Analog Control Station (IISAC01)
WBPEEUI240751?? Harmony Input/Output System
WBPEEUI240762?? IMDSO14 Digital Output Module
WBPEEUI260039?? NTMP01 Multifunction Processor Termination Unit
WBPEEUI270002?? Primary Interface, Composer
WBPEEUI270003?? Automation Architect, Composer

Related Nomenclatures
WBPEEUI230017B1 1 - 7
Related Nomenclatures
Table 1-3 lists nomenclatures related to the BRC module.
Specifications
Table 1-4 lists the specifications for the BRC module, process
bus adapter board and BRC redundancy kit.
Table 1-3. Related Nomenclatures
Nomenclature Description
IEMMU11, IEMMU12,
IEMMU21, IEMMU22
Module mounting unit
IISAC01 Analog control station
NTMP01 Field termination panel
Table 1-4. Specifications
Property Characteristic/Value
Microprocessor 32-bit processor running at 32 MHz
Memory All memory has 32-bit data path
Power requirements 5 VDC at 2 A; 10 W typical (BRC)
5 VDC at 100 mA; 0.5 W typical (PBA)
Station support 128 40-kbaud serial stations (IISAC01) or eight 5-kbaud serial stations
Redundant controller
communication link
4 MHz per byte per second (normal operation)
Programmability Function codes, C, Basic, Batch, Ladder, user-defined functions
Dimensions
BRC
PBA
35.56 mm wide, 177.80 mm high, 298.45 mm long
(1.40 in. wide, 7.00 in.high, 11.75 in. long)
31.60 mm wide, 166.12 mm high, 102.62 mm long
(1.24 in. wide, 6.54 in. high, 4.04 in. long)
Weight
BRC
PBA
0.70 kg (24.69 oz)
0.30 kg (10.6 oz)
SRAM NVRAM Flash ROM
Total
Total Available Total Available
2 Mb 1.57 Mb 512 kb 441 kb 1 Mb

1 - 8 WBPEEUI230017B1
Specifications
Communication ports 2 RS-232-C or 1 RS-232-C and 1 RS-485,
1 SAC channel (128 SACs maximum)
Ambient temperature 0° to 70°C (32° to 158°F)
Relative humidity 0% to 95% relative humidity up to 55°C (131°F) noncondensing
0% to 45% relative humidity at 70°C (158°F) noncondensing
Atmospheric pressure Sea level to 3 km (1.86 mi)
Certification CSA certified for use as process control equipment in ordinary
(nonhazardous) locations.
CE mark compliant for EMC directive and LV directive.
SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE.
Table 1-4. Specifications (continued)
Property Characteristic/Value

WBPEEUI230017B1 2 - 1
Section 2
Description and Operation
Introduction
This section explains the functionality of the Harmony bridge
controller (BRC) using block diagrams and text. Block dia-
grams divide the operation of the Harmony bridge controller.
Operation
The BRC module incorporates the power of a second genera-
tion 32-bit microprocessor operating at 32 megahertz. This is
coupled with 32-bit wide memory design with an optimized
interface. The microprocessor supplies superior performance
capable of supplanting the need for external mainframes or
minicomputers.
Control input/output is available from I/O blocks using Hnet
or from Harmony rack I/O modules using the I/O expander
bus. The data within the BRC module may be exported to the
Cnet communication network and to existing INFI-NET®and
Plant Loop communication systems.
In some processes, the effects of a control failure in the system
can create dangerous situations or cause economic loss. To
reduce the possibility of these problems occurring, redundant
modules provide fail-safe control. Redundant BRC modules
link directly to each other via the processor bus adapter (PBA)
board or the BRC redundancy kit to keep the database in the
backup module current. Each module uses a redundant high
speed communication channel to accomplish this function. If
the primary module fails, the backup module is waiting in
standby mode and immediately takes over. The backup module
has the same control strategy loaded in its memory as the pri-
mary BRC module and is ready to assume control. When oper-
ating in Hnet communication mode, the redundant
communication channel insures that single point failures will
not prevent the backup module from being in a state of readi-
ness to take over.
While the BRC module is controlling a process, it also executes
diagnostic routines. It is constantly checking the integrity of its