OPTO 22 SNAP PAC Redundancy Option User manual

SNAP PAC REDUNDANCY OPTION
USER’S GUIDE
Form 1831-180531—May 2018
43044 Business Park Drive • Temecula • CA 92590-3614
Phone: 800-321-OPTO (6786) or 951-695-3000
Fax: 800-832-OPTO (6786) or 951-695-2712
www.opto22.com
Product Support Services
800-TEK-OPTO (835-6786) or 951-695-3080
Fax: [phone]
Email: [email protected]
Web: support.opto22.com

SNAP PAC Redundancy Option User’s Guide
ii
SNAP PAC Redundancy Option User’s Guide
Form 1831-180531—May 2018
Copyright © 2014–2017 Opto 22.All rights reserved.
Printed in the United States of America.
The information in this manual has been checked carefully and is believed to be accurate; however, Opto 22 assumes no
responsibility for possible inaccuracies or omissions. Specifications are subject to change without notice.
Opto 22 warrants all of its products to be free from defects in material or workmanship for 30 months from the
manufacturing date code. This warranty is limited to the original cost of the unit only and does not cover installation, labor,
or any other contingent costs. Opto 22 I/O modules and solid-state relays with date codes of 1/96 or newer are guaranteed
for life. This lifetime warranty excludes reed relay, SNAP serial communication modules, SNAP PID modules, and modules
that contain mechanical contacts or switches. Opto 22 does not warrant any product, components, or parts not
manufactured by Opto 22; for these items, the warranty from the original manufacturer applies. Refer to Opto 22 form
1042 for complete warranty information.
Wired+Wireless controllers and brains are licensed under one or more of the following patents: U.S. Patent No(s). 5282222,
RE37802, 6963617; Canadian Patent No. 2064975; European Patent No. 1142245; French Patent No. 1142245; British Patent
No. 1142245; Japanese Patent No. 2002535925A; German Patent No. 60011224.
Opto 22 FactoryFloor, groov, groov EPIC, Optomux, and Pamux are registered trademarks of Opto 22. Generation 4, groov
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OptoTerminal, OptoUtilities, PAC Control, PAC Display, PAC Manager, PAC Project, PAC Project Basic, PAC Project Professional,
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groov includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit. (http://www.openssl.org)
All other brand or product names are trademarks or registered trademarks of their respective companies or organizations.
Opto 22
Automation Made Simple.

SNAP PAC Redundancy Option User’s Guide iii
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Table of Contents
Chapter 1: Welcome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Ethernet Link Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
System Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Redundancy Option Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SNAP-PAC-SRA Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SNAP-RPSW Redundant Power Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
PAC Control Professional and PAC Redundancy Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
About this Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Related Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Product Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Chapter 2: Connecting the Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
What You Will Need. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Configuration Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Connecting the PAC S-series Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Connecting SNAP-PAC-S2 Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Connecting SNAP-PAC-S1 Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Wiring the 7-pin Serial Connector on SNAP-PAC-S2 Controllers . . . . . . . . . . . . . . . . . . . . . . . .13
Wiring the 10-pin Serial Connector on SNAP-PAC-S1 Controllers . . . . . . . . . . . . . . . . . . . . . . .13
Wiring the 6-pin Serial Connector on the Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Connecting Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Power Connection Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Chapter 3: Configuring a Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
What You Will Need. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Assigning a Primary IP Address to ENET 1 on each Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Assigning an IP Address to the Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Creating a Control Engine for Controller Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Commissioning the Controllers for Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Checking the System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

SNAP PAC Redundancy Option User’s Guide
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Chapter 4: Creating a Strategy with Controller Redundancy . . . . . . . . . . . . . . . . . . . . 31
Glossary of Terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Persistent/Redundant Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Redundant Control Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Sequential Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Sync Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Transactional Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Creating a Redundant Strategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Step 1. Enabling the PAC Control Redundancy Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Step 2. Adding a Redundant Control Engine to a PAC Control Strategy . . . . . . . . . . . . . . . . 36
Adding an Existing Redundant Control Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Configuring an Existing Control Engine for Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Step 3. Configuring Persistent/Redundant Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Persistent/Redundant Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Configuring Redundant Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Step 4. Designing a Transactional Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Transaction Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Design Considerations and Chart Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Using Reads and Timers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
What Causes Synchronization to Occur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Adding a Sync Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Chapter 5: System Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Checking System Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Redundant System Status Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Using the Memory Map to Read Status Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Using the Memory Map to Enter and Exit Maintenance Mode . . . . . . . . . . . . . . . . . . . . . 50
Entering Maintenance Mode on Boot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Redundant System State Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Changing an IP Address on a Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Installing New Firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Installing Firmware to the Controllers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Using the Running System Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Using the Controller Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Installing Firmware to the Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Managing Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Using Advanced Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Using Controller Redundancy – Debug Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Arbiter Status LEDs and Blink Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Communication Status LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
System Status LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Resetting the Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

SNAP PAC Redundancy Option User’s Guide 1
1
1: 1: WelcomeChapter 1
1: Welcome
Welcome to the SNAP PAC Redundancy Option User’s Guide. Inside you’ll find instructions on how to
set up redundant controllers using two perfectly matched SNAP-PAC-S controllers. This guide
assumes that you understand fully how to use PAC Control™and have some familiarity with
Opto
22’s SNAP PAC System™.
In This Chapter
Introduction ..................................................................... 1
System Architecture .....................................................2
Redundancy Option Components.........................3
About this Guide............................................................ 5
Related Documentation .............................................5
Product Support............................................................. 5
Introduction
While Opto 22 Ethernet-based control systems are extremely reliable, no control system is perfect.
However, with properly configured redundant controllers, in the unlikely event that a controller were
to fail for whatever reason, a second identically configured controller takes over with almost no
down time. The SNAP PAC Redundancy Option provides the tools for developing a control system
with an increased level of reliability that can survive single points of failure, and it can improve your
system’s mean time between failures (MTBF).
A SNAP PAC System configured with the SNAP PAC Redundancy Option includes:
•Two identically matched S-series PACs
•A SNAP-PAC-SRA arbiter, a hardware device that controls which controller is active based on
status information returned by each controller in response to the arbiter’s periodic heartbeat
requests. See “SNAP-PAC-SRA Arbiter”on page 3.
•A SNAP-RPSW redundant power switch connected to the arbiter and both controllers. This
switch responds to the supply-voltage output from the arbiter, which allows it to reliably restart
a controller. See “SNAP-RPSW Redundant Power Switch”on page 4.

SYSTEM ARCHITECTURE
SNAP PAC Redundancy Option User’s Guide
2
NOTE: The SNAP-PAC-SRA arbiter and the SNAP-RPSW redundant power switch can be purchased
together in the SNAP PAC Redundancy Option Kit, part number SNAP-PAC-ROK.
•One or more Opto 22 SNAP PAC Ethernet brain-based I/O units on the same Ethernet network
as the controllers
•A PAC Control Professional strategy for use on the system’s two redundant controllers that
includes special features such as sync blocks and persistent/redundant variables. (See Chapter 4
on page 31.) Included with PAC Control Pro is the PAC Redundancy Manager, a software utility
you can use to configure and monitor the redundant PAC S-series controllers and the
SNAP-PAC-SRA arbiter.
Ethernet Link Redundancy
This guide describes only how to set up redundant controllers for your system, not Ethernet link
redundancy, which is also offered by Opto
22. Using PAC Project Professional, Ethernet link
redundancy allows you to configure redundant networks for your control system. This is achieved in
part by assigning a primary IP address to one Ethernet interface on a PAC S or PAC R controller, and a
secondary IP address to the controller’s other Ethernet interface. If communication to the primary
address fails, the secondary address takes over.
There are two basic ways to use Ethernet link redundancy:
•HMI-to-controller link redundancy, which is not supported when using redundant controllers.
For more information, see form 1700, the PAC Control User’s Guide, and form 1702, the PAC
Display User’s Guide.
•Controller-to-I/O link redundancy, which is supported when using redundant controllers. For
more information, see form 1700, the PAC Control User’s Guide.
NOTE: When using controller-to-I/O link redundancy, you must connect ENET 2 on the controllers and
I/O units to a switch. No other devices can be connected to that switch.
System Architecture
In the following simplified illustration of the redundancy architecture, two SNAP-PAC-S2 controllers
are connected via Ethernet to the same I/O. A SNAP-PAC-SRA arbiter is connected to both
controllers with dedicated RS-485 links. An Ethernet crossover cable connected to the ENET 2
Ethernet ports enables communication between the controllers. A SNAP-RSPW redundancy power
switch connected to the arbiter controls power to the controllers. Separate power supplies for the
arbiter and each of the controllers are not shown.

PAC Control Pro with Redundancy Manager
Arbiter
RS-485
RS-485
Ethernet crossover
cable connects the
PAC S2s on ENET 2
2 PAC S-series
controllers
Redundant power switch
Power
Power control
SNAP PAC brain and I/O
N-TRON Switch
CHAPTER 1: WELCOME
SNAP PAC Redundancy Option User’s Guide 3
3
Redundancy Option Components
The Redundancy Option components—S-series PACs, SNAP-PAC-SRA arbiter, and SNAP-RPSW
redundant power switch—are described below.
SNAP-PAC-SRA Arbiter
The SNAP-PAC-SRA arbiter is a stand-alone unit that monitors the
operation of the PAC S-series controllers connected to it via a
dedicated RS-485 link. If the arbiter detects improper operation of
the primary controller, the arbiter switches control to the secondary
controller. The SNAP-PAC-SRA arbiter is responsible for:
•Maintains the active/backup status of each controller in a
redundant Opto 22 system
•Sends heartbeat requests at regular intervals to each controller
in order to receive status information
•Based on the status information, sends messages that make
one controller active and put the other controller in backup
mode
•Signals the backup controller to qualify itself to be ready to take over as the active controller.
The qualification process includes matching the firmware and strategy to those on the active

REDUNDANCY OPTION COMPONENTS
SNAP PAC Redundancy Option User’s Guide
4
controller, and updating redundant variables and I/O values. If neither controller is qualified, the
arbiter favors controller #1 if both are started up within one second of each other.
•When a controller is disqualified, the arbiter tells the controller to reset itself.
•Manages the power supply of each controller using a supply-voltage output to drive
normally-closed relays in the SNAP-RPSW redundant power switch. This allows the arbiter to
reliably restart a controller ensuring that I/O never has more than one master.
SNAP-RPSW Redundant Power Switch
The SNAP-RPSW redundant power switch is a relay device designed
especially for use in a SNAP PAC redundant system. Connected to
the SNAP-PAC-SRA arbiter and both controllers, this switch responds
to the supply-voltage output from the arbiter. This allows a
controller to be restarted in order to bring the controller back up, or
to re-commission the controller after its firmware has been updated.
PAC Control Professional and PAC
Redundancy Manager
The controllers in a redundant system run a control program built
with PAC Control™Professional, one component of PAC Project™
Professional software. Also included with PAC Project Pro, the PAC
Redundancy Manager provides tools to configure the arbiter, monitor the devices in a redundant
system, install firmware on the arbiter and the controllers, and more.

CHAPTER 1: WELCOME
SNAP PAC Redundancy Option User’s Guide 5
5
About this Guide
Chapter 1: Welcome—Introduces the SNAP PAC Redundancy Option, provides information about
this guide, where to find additional information, and how to reach Opto 22 Product Support.
Chapter 2: Connecting the Hardware—Describes how to connect the serial, Ethernet, and power
cables for critical devices used in a redundant system.
Chapter 3: Configuring a Control System—Provides instructions on how to use PAC Control, PAC
Manager, and the SNAP-PAC Arbiter to configure the controllers and arbiter.
Chapter 4: Creating a Strategy with Controller Redundancy—Describes how to use the Redundancy
Option features in PAC Control to create a transactional chart.
Chapter 5: System Maintenance—Describes how to change an IP address on a controller or arbiter,
load new firmware, reset the arbiter, use the PAC Redundancy Manager advanced features, and
various other system maintenance tasks.
Related Documentation
For more information on topics related to the SNAP PAC Redundancy Option, see the following
Opto 22 documents
For this information See this guide Form
How to install and use SNAP PAC S-series
controllers SNAP PAC S-Series Controller User’s Guide 1592
How to install and use PAC Control PAC Control User’s Guide 1700
Detailed information about each command
(instruction) available in PAC Control PAC Control Command Reference 1701
.
All documents are available on our website, www.opto22.com. The easiest way to find a document
is to follow the link above or search on its form number.
Product Support
If you have any questions about using SNAP PAC Redundancy Option, you can call, fax, or email
Opto 22 Product Support. Product support is free.
Phone: NOTE: Email messages and phone
calls to Opto 22 Product Support
are grouped together and
answered in the order received.
800-TEK-OPTO (800-835-6786 toll-free
in the U.S. and Canada)
951-695-3080
Monday through Friday,
7 a.m. to 5 p.m. Pacific Time
Fax: [phone]
Email: [email protected]
Opto 22 website: www.opto22.com

PRODUCT SUPPORT
SNAP PAC Redundancy Option User’s Guide
6
When calling for technical support, be prepared to provide the following information about your
system to the Product Support engineer:
•PC configuration (type of processor, speed, memory, and operating system)
•Software and version being used
•Controller firmware version
•A complete description of your hardware and operating systems, including:
– switch configuration
– type of power supply
– types of I/O units installed
– third-party devices installed (for example, barcode readers)
•Specific error messages seen.

SNAP PAC Redundancy Option User’s Guide 7
7
2: 2: Connecting the HardwareChapter 2
2: Connecting the Hardware
This chapter describes how to connect the serial, Ethernet, and power cables for the components
used in a redundant system, including the SNAP PAC S-series controllers, the SNAP-PAC-SRA arbiter,
and the SNAP-RPSW redundant power switch. It also introduces a few basic configuration scenarios.
In This Chapter
What You Will Need ...................................................... 7
Configuration Scenarios ............................................. 8
Connecting the PAC S-series Controllers.............9
Connecting Power ......................................................14
What You Will Need
•A PC running PAC Control Professional 9.0 or higher
•A crossover cable to connect the two controllers.
•10BASE-T or 100BASE-TX Ethernet network
•The SNAP PAC Redundancy Option Kit, part number SNAP-PAC-ROK, which includes a
SNAP-PAC-SRA arbiter and a SNAP-RPSW redundant power switch
•Three SNAP-PS24 power supplies
•A functioning Ethernet-based SNAP PAC control system that includes:
– Two SNAP PAC S-series controllers that are exactly the same model, such as two
SNAP-PAC-S2s or two SNAP-PAC-S2-Ws, with firmware R9.0a or higher and loader R6.0a or
higher
– One or more Opto 22 SNAP PAC Ethernet brain-based I/O units on the same Ethernet
network as the controllers
– PAC Control strategy developed for use on the system’s two redundant controllers. See
Chapter 4 on page 31 for information on how to develop a strategy for controller
redundancy.

CONFIGURATION SCENARIOS
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8
Configuration Scenarios
As shown below there are three basic configuration scenarios. Depending on the level of protection
you require at your site, you may want to place the controllers in the same cabinet or in different
cabinets. Or you might want to put the arbiter in a different room or cabinet.
Keep the following things in mind when deciding how to configure your system:
•The system will continue to run if any single component fails or in any situation where the
currently active controller does not fail and can still communicate to I/O.
•If both the arbiter and the active controller fail simultaneously, or if the active controller fails
while the arbiter is already down, the backup will not be able to take over.
Scenario 1: Controllers and arbiter are in the same cabinet
Scenario 2: Controller 1 and Controller 2 are in separate cabinets or rooms, and the arbiter
is placed in the same cabinet or room as one of the controllers
Scenario 3: Controller 1, Controller 2, and the arbiter are in separate cabinets or rooms

CHAPTER 2: CONNECTING THE HARDWARE
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9
Connecting the PAC S-series Controllers
As shown here, two SNAP PAC S-series controllers connect to the arbiter using RS-485 serial ports.
They connect to each other on ENET 2 with an Ethernet crossover cable. See directions below for
either PAC S2s or PAC S1s. See also the diagram on page 2.
CTR1
CTR2
Serial 2
SNAP-PAC-S2 #1
SNAP-PAC-S2 #2
Serial 2
To network
Crossover cable
ENET 2
ENET 1
Ethernet connections Serial connections
This section includes the following topics:
•“Connecting SNAP-PAC-S2 Controllers”on page 10
•“Connecting SNAP-PAC-S1 Controllers”on page 11
•“Wiring the 7-pin Serial Connector on SNAP-PAC-S2 Controllers”on page 13
•“Wiring the 10-pin Serial Connector on SNAP-PAC-S1 Controllers”on page 13
•“Wiring the 6-pin Serial Connector on the Arbiter”on page 14
For pinouts of SNAP PAC S-series controllers, see form 1592, the SNAP PAC S-Series User’s Guide.

CONNECTING THE PAC S-SERIES CONTROLLERS
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10
Connecting SNAP-PAC-S2 Controllers
See also “Wiring the 7-pin Serial Connector on SNAP-PAC-S2 Controllers”on page 13 and “Wiring
the 6-pin Serial Connector on the Arbiter”on page 14.
1. Using ENET 2 on both controllers, connect the controllers to each other with a crossover cable.
To network
Crossover cable
ENET 2
ENET 1
NOTE: While not recommended, you can instead use a straight through cable to connect each
controller’s ENET 2 to your control network.
2. Using ENET 1, connect the controllers to the network.
3. Connect Serial 2 on Controller 1 to CTR1 on the arbiter using RS-485, “2-wire”mode.
4. Connect Serial 2 on Controller 2 to CTR2 on the arbiter using RS-485, “2-wire”mode.
Arbiter
CTR2
NOTES on RS-485, “2-wire”mode:
• Correct RS-485“2-wire”mode requires a single
twisted pair for the data wires and an additional
insulated wire for the signal common connection.
• It is usually easiest to use a two-pair (shielded) RS-485
data cable, as follows:
- One pair for data
- One pair for signal common
- Shield for chassis ground.
• Do NOT connect the signal common to chassis
ground.
CTR1
Common
TX/RX –
TX/RX +
Red + Black –
Pin 1
Common
TX/RX –
TX/RX +
Chassis GND
Controller
Serial 2
Arbiter
CTR1 and CTR2
Controller
ENET 2
ENET 1 Serial 2

CHAPTER 2: CONNECTING THE HARDWARE
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Connecting SNAP-PAC-S1 Controllers
See also “Wiring the 10-pin Serial Connector on SNAP-PAC-S1 Controllers”on page 13 and “Wiring
the 6-pin Serial Connector on the Arbiter”on page 14.
1. Using ENET 2 on both controllers, connect the controllers to each other with a crossover cable.
To network
Crossover cable
ENET 2
ENET 1
2. Using ENET 1, connect the controllers to the network.
3. Connect Serial 2 on Controller 1 to CTR1 on the arbiter using RS-485, “2-wire”mode.
4. Connect Serial 2 on Controller 2 to CTR2 on the arbiter using RS-485, “2-wire”mode.

Controller
Serial 2
ENET 2
ENET 1
Arbiter
CTR2
CTR1
Common
TX/RX –
TX/RX +
Red + Black –
Pin 1
Common
TX/RX –
TX/RX +
Chassis GND
Controller
Serial 2
Arbiter
CTR1 and CTR2
NOTES on RS-485, “2-wire”mode:
• Correct RS-485 “2-wire”mode requires a single
twisted pair for the data wires and an additional
insulated wire for the signal common connection.
• It is usually easiest to use a two-pair (shielded) RS-485
data cable, as follows:
- One pair for data
- One pair for signal common
- Shield for chassis ground.
• Do NOT connect the signal common to chassis
ground.
CONNECTING THE PAC S-SERIES CONTROLLERS
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CHAPTER 2: CONNECTING THE HARDWARE
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Wiring the 7-pin Serial Connector on SNAP-PAC-S2
Controllers
Each serial port on the SNAP-PAC-S2 uses a 7-pin pluggable connector supplied with the controller
(EBY part number EB1381M-07-500 or equivalent). Use the screws on the side of the connector to
insert or remove wires.
CAUTION: Do not use communication port connectors from a legacy OptoControl controller*. Legacy
connectors will fit in a SNAP-PAC-S2, but the pin orientation is different. Instead, use the connectors
supplied with the SNAP-PAC-S2 controller.
*Legacy OptoControl Controllers
G4LC32
G4LC32SX
G4LC32ISA
G4LC32ISA-LT
M4
M4IO
M4RTU
SNAP-LCM4
SNAP-LCSX/PLUS
Wiring the 10-pin Serial Connector on SNAP-PAC-S1
Controllers
Serial ports 1 and 2 on SNAP-PAC-S1 controllers share a 10-pin pluggable connector (Phoenix
Contact, part number FK-MC 0.5 - 2.5, supplied with the controller).
When inserting and removing wire leads into this connector:
1. Completely depress the small orange tab for the appropriate opening with a small screwdriver.
2. While holding the tab down with the screwdriver, insert or remove the wire as needed.

CONNECTING POWER
SNAP PAC Redundancy Option User’s Guide
14
3. Release the orange tab.
Hole
Orange tab
Pin 1
Wiring the 6-pin Serial Connector on the Arbiter
The RS-485 serial ports on the SNAP-PAC-SRA arbiter use a 6-pin pluggable connector (Phoenix
Contact, part number FK-MC 0,5/06 - 2.5, supplied with the arbiter). When inserting and removing
wire leads into this connector:
1. Completely depress the small orange tab for the appropriate opening with a small screwdriver.
2. While holding the tab down with the screwdriver, insert or remove the wire as needed.
3. Release the orange tab.
Hole
Orange tab
Connecting Power
Using the Power Connection Diagram on page 15, connect power to the arbiter, controllers, and
switch as follows:
1. Connect one of the three SNAP-PS24 power supplies to the SNAP-PAC-SRA arbiter.
2. Connect a power supply to Side 1 of the SNAP-RPSW switch.
3. Connect a power supply to Side 2 of the switch.
4. Connect power from Side 1 on the switch to Controller 1.
5. Connect power from Side 2 on the switch to Controller 2.
6. Connect control wires from the arbiter to Side 1 and Side 2 on the switch.
Now you are ready to configure the redundant system devices. Go the next chapter,
Chapter 3: Configuring a Control System.

black/white wire
red/white wire (+)
Power Connection Diagram
CHAPTER 2: CONNECTING THE HARDWARE
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CONNECTING POWER
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