ControlNet PLC-5 Hot Backup System Cat. No.
Important User Information Because of the variety of uses for the products described in this publication, those responsible for the application and use of these products must satisfy themselves that all necessary steps have been taken to assure that each application and use meets all performance and safety requirements, including any applicable laws, regulations, codes and standards.
Rockwell Automation Support Before you contact Rockwell Automation for technical assistance, we suggest you please review the troubleshooting information contained in this publication first. If the problem persists, call your local Rockwell Automation representative or contact Rockwell Automation in one of the following ways: Phone Internet United States/Canada 1.440.646.5800 Outside United States/Canada You can access the phone number for your country via the Internet: 1. Go to http://www.ab.com 2.
Notes
Preface Manual Objectives This manual shows you how to set up and apply a ControlNetTM PLC-5® Hot Backup system. A backup system requires a pair of standard PLC-5/40TM or PLC-5/80TM ControlNet programmable controllers (Series F, Revision A or higher), with I/O remotely connected to both PLC-5s via ControlNet. IMPORTANT For the ControlNet PLC-5 programmable controllers to operate in backup mode, each PLC-5 must have a new ControlNet Backup Cartridge (Cat. No.
Preface 2 What This Manual Contains Refer to the following table to guide you through the information contained in this manual.
Preface Related PLC-5 Publications 3 Related documentation for ControlNet and other PLC-5 programmable controllers is available: Publication Publication Number Enhanced PLC-5 Processor System Overview 1785-2.36 Enhanced and Ethernet PLC-5 Programmable Controllers User Manual 1785-6.5.12 ControlNet PLC-5 Programmable Controllers User Manual 1785-UM022 ControlNet PLC-5 Programmable Controllers Quick Start 1785-QS006 1785-PLC-5 Programmable Controllers Quick Reference 1785-7.
Preface 4 For more information on any of the software components of the ControlNet PLC-5 backup system (e.g., RSLogix 5, RSLinx, and RSNetWorx), refer to the software documentation and online help for the individual software packages.
Summary of Changes Summary of Changes The information below summarizes the changes to the ControlNet PLC-5 Hot Backup System User Manual. New Features and Information The following table highlights new features and information for the Hot Backup system and its location in this manual.
Summary of Changes 2 Notes Publication 1785-UM024B-EN-P - January 2003
Table of Contents Preface Manual Objectives. . . . . . . . . . . Who Should Use This Manual . . What This Manual Contains . . . . Terms and Conventions. . . . . . . Related PLC-5 Publications . . . . Related ControlNet Publications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Table of Contents iv Advanced Configuration Options . . . . . . . . . . . . . . . . . . Configuring Optional Parameters in a Backup System Synchronous and Asynchronous Program Scanning . . Equivalence Checks . . . . . . . . . . . . . . . . . . . . . . . . . Crossloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . System Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crossloading Over Data Highway Plus . . . . . . . . . . . Requalification of Dual Primary Processors. . .
Table of Contents v Qualification: From No Control State to Primary State . . B-6 Qualification: From No Control State to Secondary State B-7 Reasons for Qualification Major Fault . . . . . . . . . . . . . B-14 Switchover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-14 Qualified Switchovers . . . . . . . . . . . . . . . . . . . . . . . . B-15 Unqualified Switchovers. . . . . . . . . . . . . . . . . . . . . . . B-16 Switchover Considerations . . . . . . . . . . . . . . . . . . . . .
Table of Contents vi Sequential Process Application Considerations . . . . . . . . . . What Causes a PLC-5 to Get Into an Incorrect State . . . . How to Keep the Controllers in the Same Process State . When the Controllers are in Different States . . . . . . . . . Complete Qualification in the Same Process State . . . . . Comparison to the 1785-BCM System Glossary Publication 1785-UM024B-EN-P - January 2003 E-5 E-6 E-7 E-8 E-9 Appendix F Chapter Objectives . . . . . . . . . . . . . . . . . . . . . .
Chapter 1 Backup Concepts for the ControlNet PLC-5 Hot Backup System Chapter Objectives This chapter describes why and how to use the ControlNet PLC-5 backup system and its basic system architecture. Why Use a Backup System? The objective of any redundant system (i.e., backup system) is to improve the amount of up-time of a machine or process by ensuring consistent availability of that machine. This also reduces costs associated with equipment failure.
1-2 Backup Concepts for the ControlNet PLC-5 Backup System Basic System Architecture The following illustration describes the various components of the basic ControlNet PLC-5 hot backup system: TM TM How the Backup System Works In a ControlNet PLC-5 hot backup system, one PLC-5 programmable controller, referred to as the primary programmable controller, controls the operation of the ControlNet I/O.
Backup Concepts for the ControlNet PLC-5 Backup System 1-3 Qualification When bringing the secondary programmable controller of a backup system online, it is important to ensure that it is in a state that will enable it to take over the control of the system in the event of a primary failure. This process of verifying and conditioning the state of the secondary programmable controller is known as qualification. Switchover will not occur without a qualified secondary programmable controller.
1-4 Backup Concepts for the ControlNet PLC-5 Backup System Equivalence Checking Backup systems are traditionally designed in a way such that both the primary and secondary programmable controllers are programmed with identical applications. This allows for the controlled process to continue with normal production operation in the event of a primary programmable controller failure.
Backup Concepts for the ControlNet PLC-5 Backup System 1-5 Switchover Switchover is what occurs when the secondary programmable controller assumes control of the process, thus becoming the primary programmable controller. Several conditions can cause this to happen: • critical failures in the primary programmable controller (e.g., hardware faults) • internal conditions within the primary programmable controller (e.g.
1-6 Backup Concepts for the ControlNet PLC-5 Backup System Notes Publication 1785-UM024B-EN-P - January 2003
Chapter 2 Understanding the ControlNet PLC-5 Hot Backup System Components Chapter Objectives This chapter describes the components that make up the ControlNet PLC-5 hot backup system. Hardware Components • two PLC-5 ControlNet programmable controllers (either 1785-L40C15 or 1785-L80C15, Series F, Revision A or later) Each programmable controller must be in a separate 1771 chassis, and each chassis must have its own power supply.
2-2 Understanding the ControlNet PLC-5 Hot Backup System Components • ControlNet network cables, taps, and terminators for making connections between the PLC-5 programmable controllers and the I/O adapters • a PC with a 1784-KTCX15 card, or a laptop computer with a 1784-PCC card • other ControlNet devices, including HMI (optional) Software Components The basic ControlNet PLC-5 backup system includes the following software components: • RSLogix 5 programming software (Release 3.
Understanding the ControlNet PLC-5 Hot Backup System Components 2-3 Compatibility Considerations If the firmware series or revision do not match between the two programmable controllers in a backup system, one or both programmable controllers will detect an incompatibility and indicate a Major Fault code 238. If the fault is cleared without correcting the compatibility issue, the fault will continue to occur.
2-4 Understanding the ControlNet PLC-5 Hot Backup System Components Summary of Required Hardware, Firmware and Software The following table summarizes hardware, firmware and software requirements. Additionally, the table describes major enhancements and in what revision of firmware they were made.
Understanding the ControlNet PLC-5 Hot Backup System Components ControlNet Backup Cartridge 2-5 Each ControlNet PLC-5 programmable controller requires a 1785-CHBM/A ControlNet backup cartridge, inserted into the PLC-5 EEPROM memory cartridge slot, to enable backup functionality. The ControlNet backup cartridge contains EEPROM memory cartridge functionality (i.e.
2-6 Understanding the ControlNet PLC-5 Hot Backup System Components Notes Publication 1785-UM024B-EN-P - January 2003
Chapter 3 Installing and Configuring Your ControlNet PLC-5 Backup System Chapter Objectives This chapter outlines the steps you must perform to install the backup system components, and to subsequently configure them to create a functioning backup system. Installing the Hardware Before you begin, be sure that you have all of the required hardware components, as listed in Chapter 2. Follow these steps to install the required hardware for your backup system. 1.
3-2 Installing and Configuring Your ControlNet PLC-5 Backup System 6. Wire the ControlNet network to the PLC-5 processors and to the ControlNet I/O adapters being used for the backup system. IMPORTANT Make certain that both ControlNet Hot Backup PLC-5s and the Hot Backup I/O are on the same ControlNet network. Bridging to another ControlNet network is not allowed. The network cabling may consist of single or redundant channels.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-3 Configuring With a Single Control Application This section assumes that you have already developed your control application and have loaded it onto a single ControlNet PLC-5 processor (i.e., a non-backup system). Throughout this section, we will refer to this processor as the first processor. Furthermore, we assume that you have a second processor installed, powered on, and in its default state.
3-4 Installing and Configuring Your ControlNet PLC-5 Backup System The Scanlist Configuration screen appears. 4. For each entry under the Connection Name column, double click on Exclusive Owner, choose Redundant Owner from the pull-down menu, and press Enter. Configure Handshaking Messages With RSNetWorx Within your backup system, you must use RSNetWorx to set up the send and receive scheduled messages that allow handshaking to occur between the two ControlNet PLC-5s that comprise your backup system.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-5 The Connection Properties dialog box appears. The To Node field is already filled in for you. This number indicates the node number from which you will receive the Consume Buffer ID scheduled message. In your ControlNet backup system, the odd-numbered node will receive the message from the even node, and vice versa. 2. Double click under the Value field to select the message number you wish to assign to identify this message.
3-6 Installing and Configuring Your ControlNet PLC-5 Backup System Note that the message number for the Consume Buffer ID message must match the message number of the corresponding Produce Buffer ID message. The node number and message number are used together to identify the specific message. 3. In the Requested Packet Interval field, enter an RPI value for this message from 1 to 32,767. (For purposes of this example, we will use an RPI value of 5ms.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-7 Configure ControlNet I/O on the Second PLC-5 Configure all ControlNet I/O adapters and modules that will be in your backup system, and ensure that the ControlNet I/O mapping and data file assignments on the second PLC-5 match those on the first PLC-5. IMPORTANT RSNetWorx for ControlNet does not automatically assign the same data file addresses for redundant connections on different PLC-5 programmable controllers.
3-8 Installing and Configuring Your ControlNet PLC-5 Backup System Configure the Hot Backup Parameters 1. Launch RSLogix 5. 2. From the Comms menu, choose System Comms. The Communications dialog appears: 3. Click on the odd-numbered node address of the first PLC-5. 4. Click the Online button to connect to the processor. The Going to Online Programming State dialog appears: 5. Click on Upload Logic, Merge with Existing File’s Comment/Symbol DB button to confirm that you wish to complete the upload.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-9 The ControlNet Hot Backup screen appears, with the Configure tab selected. 8. Set the following: • Backup File - Enter an unused data file number. This creates a 200-word integer file to be used as the ControlNet Backup Configuration and Status file. • Odd Node Address - Enter the ControlNet node address corresponding to the odd node processor.
3-10 Installing and Configuring Your ControlNet PLC-5 Backup System 1. In RSLogix 5, open the project associated with the first PLC-5, offline. 2. From the File menu, choose Save As, and save the project under a new name for the second PLC-5. 3. Go online with the even-numbered ControlNet node. 4. From the Comms menu, choose System Comms. The Communications dialog appears:. 5. Click on the even-numbered node address of the second PLC-5. 6. Choose Download to download the project to the second PLC-5. 7.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-11 Configuring With Differing Applications This section assumes that: • you intend for the secondary PLC-5 in your backup system to run a different application than the primary PLC-5 • you have already developed separate control applications for the primary and secondary PLC-5s • the control applications are loaded onto their respective PLC-5s • both PLC-5s are powered on, are in Program mode, and are physically connected to the ControlNet
3-12 Installing and Configuring Your ControlNet PLC-5 Backup System The Scanlist Configuration screen appears. 4. For each entry under the Connection Name column, double click on Exclusive Owner, choose Redundant Owner from the pull-down menu, and press Enter. Configure Handshaking Messages With RSNetWorx Within your backup system, you must use RSNetWorx to set up the send and receive scheduled messages that allow handshaking to occur between the two ControlNet PLC-5s that comprise your backup system.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-13 The Connection Properties dialog box appears. The To Node field is already filled in for you. This number indicates the node number from which you will receive the Consume Buffer ID scheduled message. In your ControlNet backup system, the odd-numbered node will receive the message from the even node, and vice versa. 2. Double click under the Value field to select the message number you wish to assign to identify this message.
3-14 Installing and Configuring Your ControlNet PLC-5 Backup System 6. Right click on the odd-numbered node (Node 1 in this example) and choose Insert Connection. The Connection dialog box appears. The To Node field is already filled in for you. This number indicates the node number from which you will receive the Consume Buffer ID message. In your ControlNet backup system, the odd-numbered node will receive the message from the even node, and vice versa. 7.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-15 The Scanlist Configuration screen appears. 4. For each I/O adapter entry under the Connection Name column, double click on Exclusive Owner, choose Redundant Owner from the pull-down menu, and press Enter. 5. From the File menu, choose Save to save the completed ControlNet configuration. Configure the Hot Backup Parameters on the First PLC-5 1. Launch RSLogix 5. 2. Go online with the odd-numbered ControlNet node. 3.
3-16 Installing and Configuring Your ControlNet PLC-5 Backup System 5. Click the Online button to connect to the PLC-5. The Going to Online Programming State dialog appears: 6. Click on Upload Logic, Merge with Existing File’s Comment/Symbol DB button to confirm that you wish to complete the upload. This step is required since you have made changes to the ControlNet configuration. 7. From the File menu, choose Save to save the project. 8.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-17 9. Set the following: • Backup File - Enter an unused data file number. This creates a 200-word integer file to be used as the ControlNet Backup Configuration and Status file. • Odd Node Address - Enter the ControlNet node address corresponding to the odd node processor. • Send Message - Enter the message number of the from the Produce Buffer ID from the odd-numbered node address (refer to the number you recorded on page 3-6.
3-18 Installing and Configuring Your ControlNet PLC-5 Backup System Advanced Configuration Options The procedures in the previous sections outlined the steps required to configure a basic ControlNet PLC-5 backup system. In addition, there are other options you can configure for the backup system. In addition to the information provided here, you can find specific details on these features in the appendices of this manual.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-19 • User Program Control for Completion of Qualification you can control when qualification completes by setting and clearing word 39 in the CBI file. For more information on how to use this feature, refer to page 5-11. • Designated Primary - you can force the processor at the odd node address to always be the primary PLC processor as long as that processor is in Run mode and is qualified.
3-20 Installing and Configuring Your ControlNet PLC-5 Backup System Synchronous and Asynchronous Program Scanning One of the most important considerations when implementing a backup system is the effect of divergence on the system. Divergence occurs when the primary and secondary controllers are running their applications and scanning the I/O asynchronously to each other.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-21 You can change the operational mode from the Configure tab of the ControlNet Hot Backup screen:. Note: When you choose Synchronous mode, you will have to enter a Maximum Program Scan Time as well. Before selecting Synchronous mode, enter a value into the Max Program Scan Time field. This value should be slightly larger than the maximum program scan time recorded in the Processor Status file.
3-22 Installing and Configuring Your ControlNet PLC-5 Backup System Equivalent indicates that the two processors are identical, and Different indicates that there were differences detected. Refer to Appendix B for more information on equivalence checking. Crossloading You can perform data table crossloading on demand. While both PLC processors are running, you can initiate a crossload from either the primary or secondary processor.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-23 Once you have selected the files you wish to crossload, click on the Crossload User Files button to perform the operation. Note that you can perform a crossload for individual files and for a range of files simultaneously. System Status You can view system status from the Status tab of the ControlNet Hot Backup screen. The CBC Module LEDs section mirrors the display of the LEDs on the 1785-CHBM module which is currently online.
3-24 Installing and Configuring Your ControlNet PLC-5 Backup System Invalid State Reason If the system is in an Invalid backup state (refer to Appendix B for more information on backup states), a description of the problem is displayed. Refer to chapter 5 for information on corrective actions you can take. Maximum Pscan Information This information is applicable for Synchronous mode operation only.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-25 For the point-to-point DH+ network between the processors, set the DH+ address based upon the ControlNet node address being an even or odd number, as shown in the following table: To set: Set switch(es): an odd-numbered ControlNet address 1 2-6 an even-numbered ControlNet address 1 2 3-6 Baud Rate 7 To: Up Down Down Up Down Up (230.
3-26 Installing and Configuring Your ControlNet PLC-5 Backup System Requalification of Dual Primary Processors You can select to requalify a PLC-5C Hot Backup processor if dual primary processors exist. This will avoid a major fault. Additionally, this feature increases the availability of a qualified backup system if communication is broken between the two PLC-5 processors.
Installing and Configuring Your ControlNet PLC-5 Backup System 3-27 Downloading Editing Changes Downloading a program saved from one processor to another can greatly simplify the transfer of editing changes from one processor to another. If you follow the steps described earlier in this chapter, in the section entitled “Create and Download the Project for the Second PLC Processor,” then you can complete this processor-to-processor download.
3-28 Installing and Configuring Your ControlNet PLC-5 Backup System Notes Publication 1785-UM024B-EN-P - January 2003
Chapter 4 Using I/O in Your ControlNet Hot Backup System Chapter Objectives This chapter describes special considerations when using I/O in a hot backup system. Considerations when Using I/O For scheduled connections, a special connection type has be established called a redundant connection. A redundant connection allows both processors to make identical scheduled connections and only the outputs from the primary processor are used. The outputs from the secondary processor are discarded.
4-2 Using I/O in Your ControlNet Hot Backup System This non-redundant I/O should only be used when all the consequences of its operation are fully understood. Redundant Connections Redundant connections are required so that the PLC-5 ControlNet Hot Backup system can properly switch over ownership of the scheduled output from the former primary PLC-5 to the current primary PLC-5.
Using I/O in Your ControlNet Hot Backup System 4-3 Redundant connection parameters consist of: • • • • • Input size Output size RPI Data Table Module configuration size Data Table Module configuration data (with the number of words depending on the module type) • any other connection-dependent configuration parameters such as Fault Action and Idle Action. You configure these parameters in RSNetWorx for ControlNet software.
4-4 Using I/O in Your ControlNet Hot Backup System 3. Use RSLogix5 to make all the desired I/O configuration changes to the primary PLC-5. and accept all the changes. This will temporarily close and open the scheduled connections. 4. Save the project in RSNetWorx and accept the pending edits. Do a merged save.This makes the corresponding I/O configuration changes to the PLC-5 in Program mode without affecting the primary PLC-5. 5.
Using I/O in Your ControlNet Hot Backup System 4-5 OOV is done via a round-robin poll that runs in the background of the primary PLC-5. EXAMPLE In an application with 20 redundant connections, the primary PLC-5 polls these redundant connections sequentially until all of the redundant connections have been polled. For each redundant connection that indicated the primary processor is not the owner of the outputs for that connection, the value in word 8 of the CBI file increments.
4-6 Using I/O in Your ControlNet Hot Backup System With CIO read instructions, there are two possibilities: • either both programmable controllers can perform the read, or • the primary PLC-5 can perform the read and then the data can be crossloaded from the primary to the secondary PLC-5 Considerations when Using CIO Instructions Be aware of certain considerations when using CIO instructions for an I/O module that has redundant connections configured for that module.
Using I/O in Your ControlNet Hot Backup System 4-7 There are two areas of concern with HMI devices in a PLC-5 ControlNet Hot Backup System: • the data gathered by the HMI device must only gather it from the primary PLC-5. There are special requirements that allow the HMI device to determine which of the programmable controllers is the primary. • data that is written to the PLC-5 by the HMI device must be sent by the HMI device to both programmable controllers.
4-8 Using I/O in Your ControlNet Hot Backup System The application must only gather data from the PLC-5 whose primary bit was set. If both programmable controllers have their primary bit off, then neither PLC-5 is the primary and it does not matter from which PLC-5 the data is gathered. If the data going to the HMI device must be sent periodically, it may be easier to have the PLC-5 write the data to the HMI instead of having the HMI read the data from the PLC-5.
Using I/O in Your ControlNet Hot Backup System 4-9 This procedure assumes that the HMI knows which PLC-5 is the primary programmable controller. Refer to the above procedures to determine the primary PLC-5. Checking ControlNet Resources When an HMI device is connected to the PLC-5, it uses the some of the limited resources of the PLC-5. The PLC-5 keeps diagnostic information on its resources in its ControlNet diagnostics file.
4-10 Using I/O in Your ControlNet Hot Backup System Notes Publication 1785-UM024B-EN-P - January 2003
Chapter 5 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Chapter Objectives This chapter describes the diagnostic capabilities of the ControlNet PLC-5 backup system, and provides you with tips to help you in troubleshooting difficulties with your system. The PLC-5 ControlNet backup system generates diagnostic information to assist you with troubleshooting problems that may arise within a backup application.
5-2 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System ControlNet PLC-5 Backup-Specific Major Fault Error Codes The PLC-5 processor stores major fault codes in word 12 of the processor status file (S:12). The following table lists new major fault codes specific to the ControlNet Hot Backup processor and the suggested corrective action for each.
Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Using the 1785-CHBM Cartridge Status Indicators 5-3 The 1785-CHBM cartridge status indicators indicate the operational state of the ControlNet PLC-5 backup system. The following table lists the various LED states and the recommended action: LED Color Indicates PRI Green This processor is the primary (i.e., it controls the Normal operation outputs).
5-4 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System LED Color Indicates Probable Cause Corrective Action SYNC Green The system is operating in synchronous mode, and this processor has never exceeded the adjusted maximum program scan time parameter. Normal operation No action required Red The system is operating in synchronous mode, and this processor has been out of sync (i.e., its actual program scan time has exceeded the adjusted maximum program scan time parameter).
Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System If you see reason code: 0 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 Which indicates this condition: 5-5 Take this corrective action: Valid backup state No action required Receive handshake connection not found in I/O Map Configure the handshake connections in the I/O map table. Table Enter the handshake connection numbers in words 1 and 2 of the ControlNet Backup Configuration and Status file.
5-6 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Troubleshooting Qualification Major Faults If you see reason code: 0 1 2 3 When a qualification major fault occurs (S:12 = 234), the ControlNet Backup Configuration and Status file contains a diagnostic word (word 46) that indicates the reason why the qualification major fault occurred. The following table lists the various qualification major fault reason codes and the suggested corrective action.
Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Troubleshooting Qualification Crossloads 5-7 If the data table structures are the same between the two processors, data table crossloads automatically occur during qualification. Should the Qualification Data Table crossloads fail, the processor major faults. (Refer to Appendix C for more information on data table crossloading.
5-8 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System This puts the system in a state where the secondary processor controls some outputs and the primary processor controls the remaining outputs. This system state may not be acceptable in certain applications. IMPORTANT To be notified of this system state, you must poll the output ownership verification feature. Output ownership verification is done via a round-robin poll that runs in the background of the primary processor.
Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Word Definition 3 Backup state of the processor. Valid values include: 0 - Invalid 1 - No Control 2 - Primary 4 - Secondary 4 Qualification state of the system. Valid values include: 0 - No qualified secondary present 1 - Qualified secondary present 5 Reason code indicating why the processor is in the Invalid backup state. This word is constantly updated until the processor is no longer in this state.
5-10 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Publication 1785-UM024B-EN-P - January 2003 Word Definition 11 Equivalence checks; there are 6 bits defined (i.e., one bit per equivalence check). If a bit is set, the corresponding equivalence check will be performed. If the bit is not set, no check is performed. By default, all equivalence checking is enabled. The remaining 10 bits in the word must be set to 0.
Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Word Definition 30 Accept Configuration Changes. A non-zero value written into this location forces the primary PLC-5 processor to accept the new configuration parameters. After the PLC-5 processor has done so, it will zero this word. This command is only in effect for the primary processor.
5-12 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Publication 1785-UM024B-EN-P - January 2003 Word Definition 46 Qualification status. The reason code for why the processor failed qualification or if the configuration parameters were changed by the primary.
Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Word Definition 53 Crossload Status. This is a Message instruction error code. The processor writes the value into this word. For information on error descriptions, refer to your PLC-5 Instruction Set Reference Manual. 54 Crossload Failed File. This word displays the file number on which the crossload failed. The crossload status word located in word 53 displays the error code and word 54 displays its correlated file.
5-14 Monitoring and Troubleshooting Your ControlNet PLC-5 Hot Backup System Notes Publication 1785-UM024B-EN-P - January 2003
Appendix A Specifications Specifications The following specifications are for the 1785-CHBM cartridge.
A-2 Specifications Notes Publication 1785-UM024B-EN-P - January 2003
Appendix B Backup States Chapter Objectives This Appendix describes the possible backup states and backup state transitions of the PLC-5 ControlNet backup system.
B-2 Backup States Invalid Backup State When an improper backup configuration exists, the PLC-5 ControlNet backup system goes into the Invalid backup state. Both the Primary and Secondary LEDs on the 1785-CHBM cartridge are solid red when the system is in this state, and the Qualified and Synchronous LEDs are off. If you switch the system to Run mode while in the Invalid backup state, a major fault occurs. (Refer to Chapter 5 for definitions of the major fault codes.
Backup States B-3 – Maximum program scan time (invalid if greater than (128 x NUT) and synchronous operational mode) – Crossload File 1, Crossload File 2, Crossload File Low, and Crossload File High (invalid if greater than or equal to 1000) – Crossload over DH+ (invalid if not equal to 0 or 1) – Requalification of dual primary PLC-5s (invalid if not equal to 0 or 1) While in the Invalid backup state, you can set default parameters for the optional configuration parameters by intentionally entering an inc
B-4 Backup States If there is a valid partner PLC-5 ControlNet backup system, and the systems are connected on the ControlNet channel, the Qualified LED is solid yellow. This indicates that the necessary configuration needed to allow the backup pair to successfully communicate with each other has been achieved. You can make any configuration changes you wish to the ControlNet Backup Configuration and Status file while the PLC-5 processor is in the No Control backup state.
Backup States B-5 Lonely Primary Backup State The Primary LED is solid green if there is at least one good scheduled connection on the ControlNet channel. If there are no good scheduled connections on the ControlNet channel the Primary LED blinks green. This is referred to as the Lonely Primary backup state. Since there are no valid scheduled connections on the ControlNet channel, this PLC-5 is not controlling the system outputs on the ControlNet channel.
B-6 Backup States Backup State Transitions In the previous section, we described the possible states of the PLC-5 ControlNet backup system, with references to transitions between states. For example, when in the No Control backup state, if you change a configuration parameter to an invalid value, the PLC-5 ControlNet backup system transitions into the Invalid backup state. This section describes two backup state transitions: Qualification and Switchover.
Backup States B-7 Qualification: From the No Control State to the Secondary State The backup state transition from No Control backup state to Secondary backup state occurs when the PLC-5 system transitions from Program mode to Run mode, and the partner PLC-5 processor is in the Primary backup state and is communicating with this PLC-5 processor.
B-8 Backup States • Backup configuration parameters passed to qualifying system After the qualifying PLC-5 system has waited, if necessary, for the qualification connection delay, the backup configuration parameters are passed from the primary PLC-5 system to the qualifying PLC-5 system. The backup configuration parameters which were originally in the qualifying system are overwritten and lost.
Backup States B-9 There are 6 different areas in which equivalence checking can be performed: – Program File Structure and Program Files - This checksum is calculated for all the Program files, with the notable exception of SFC files. This checksum continues to be calculated when the backup system is qualified. This allows status to be available regarding whether the Program file checksums differ for a qualified backup system. Note: This should only be used when the data table structures are the same.
B-10 Backup States No SFC information is included in the Force Tables checksum. Also, note that you cannot perform forcing on DIF or DOF files. – Status File - This checksum is calculated for various configured words in the Status File, and continues to be calculated when the backup system is qualified. This allows status to be available regarding whether the Status File checksums differ for a qualified backup system.
Backup States B-11 PLC, we recommend that you disable equivalence checking first to avoid the condition where a PLC-5 processor cannot become qualified due to failing an equivalence check. Once all the edits are tested and placed into both PLC-5 systems, you can reenable the equivalence check. Word 49 in the ControlNet Backup Configuration and Status file gives you equivalence check status for a qualified backup system.
B-12 Backup States Though the complete Status File is not crossloaded, there are six words in this file that are transferred from the primary system to the qualifying system. These six words are the real-time clock. The Qualification Data Table crossload does not occur if the Data Table Structures are not the same. If you want to ensure that a Qualification Data Table crossload occurs, you must enable equivalence checking for the Data Table structure area.
Backup States B-13 It may take many seconds for the Qualification State Data Table crossload to finish. The time it takes to complete the data table crossload primarily depends on the amount of data table data to be crossloaded. Even though the State Data Table crossload may take many seconds to complete, the data that is transferred from the primary system to the qualifying system is fresh.
B-14 Backup States If you selected the Designated Primary feature, and the odd node of the odd-even backup pair has just gone through secondary qualification, a switchover automatically occurs. The odd node becomes the primary system, and the even node transitions from the primary system to the secondary system. The even node’s transition from primary to secondary happens immediately. The even node does not go through qualification when it becomes the secondary system.
Backup States B-15 There are two categories for switchovers: • Qualified Switchovers • Unqualified Switchovers Qualified Switchovers Qualified Switchovers are switchovers that transition the primary processor to the Secondary backup state and the secondary processor to the Primary backup state. Thus after a Qualified Switchover, there is still a qualified backup system.
B-16 Backup States status tab of the ControlNet Hot Backup screen. Once the Forced Switchover is activated, the processor writes a zero into the Forced Switchover word of the Backup Integer File. You can activate this switchover from either the primary or secondary processor. Forced Switchover is useful when you want to test edits you have made in your application program. In this case, you make edits to the secondary system, force a switchover, and monitor the results of the edits.
Backup States B-17 If the output values in the data tables are different between the primary and secondary systems, there will be a bump in the outputs when the new primary processor takes control of the outputs. There are features in the PLC-5 ControlNet backup system which minimize the divergence of outputs between the primary and secondary processors. These features are synchronized program scans and data table crossloads.
B-18 Backup States – Problems with the ControlNet network which causes loss of the handshake connection with the primary processor. The formula that determines the length of time the secondary system waits before timing out the primary processor is as follows: Primary Timeout = 5 + (3 * NUT) or 25ms, whichever is greater. So, if the NUT is 5ms, the Primary Timeout is 25ms. If the NUT is 10ms, the Primary Timeout is 35ms. The Primary Timeout is not the only factor in the Timeout Switchover Time.
Appendix C Data Table Crossloading Chapter Objectives This appendix provides you with reference information on the data table crossloading feature. Data Table Crossloading Data table crossloading is a feature you can enable to minimize the bump in system outputs when a processor switchover occurs. This feature is most useful when identical PLC-5 processors are used in the backup system.
C-2 Data Table Crossloading An On-Demand data table crossload transfers data table data from the primary processor to the secondary processor. To set up On-Demand data table crossload operations, you must load configuration information, identifying the files to be crossloaded. Then, to trigger an On-Demand data table crossload, you must enter a non-zero value into word 33 of the ControlNet Hot Backup Integer file.
Data Table Crossloading C-3 On-Demand Data Table Crossloads It may be necessary for you to crossload data table data after the backup system has a qualified secondary processor. For example, the Timer Accumulators may have diverged between the primary and secondary processor over time. Or, you may have modified some data table values on the primary processor and would like to copy those values into the secondary processor.
C-4 Data Table Crossloading • PD Files The entire PD file structure is crossloaded during the On-Demand data table crossload from the primary processor to the non-primary processor. All PD files are crossloaded, as well as all elements in the PD files. You are not able to crossload a subset of PD file types (i.e., if there are 20 PD data table files, all 20 PD data table files will be crossloaded).
Data Table Crossloading C-5 – ControlNet I/O Status File – ControlNet Diagnostic File IMPORTANT If a file in the On-Demand crossload User Selectable files is either a Timer or Counter file type, only the Accumulator for each file element is crossloaded. The timer and counter presets are not crossloaded. If you want them to be crossloaded, you must use a different crossloading mechanism.
C-6 Data Table Crossloading The On-Demand data table crossload operations that get performed depend on the value written into the On-Demand Crossload Command word. The 4 least significant bits of the On-Demand Crossload Command word are defined for the 4 different On-Demand data table crossload operations.
Data Table Crossloading C-7 Qualification Data Table Crossload The Qualification data table crossload occurs when a processor in the No Control state transitions from Program mode to Run mode, and the other processor is the primary processor. This complete data table crossload is performed while the qualifying PLC-5 system is still in Program mode.
C-8 Data Table Crossloading The Qualification State data table crossload is almost identical to the On-Demand data table crossload discussed previously.
Data Table Crossloading C-9 Effect of Data Table Crossloading on the ControlNet Channel Data table crossloading only transfers one file at a time. Also, only one unscheduled buffer is used at any one time. So the impact of the data table crossloading on available ControlNet channel unscheduled bandwidth should be minimal. Also, the impact of data table crossloading on the available unscheduled buffers is minimal.
C-10 Data Table Crossloading These error codes are identical to the Message Instruction Error Codes. See the Instruction Set Reference Manual (Publication 6200-6.4.11) for a complete listing of the various error codes which can be encountered while executing a Message Instruction. For example, a qualification crossload could fail if the data table file on the primary processor had read privileges disabled. This error would show up as error code 0xF00B (privilege error) in word 53 of the CHBI file.
Appendix D Program Synchronization Chapter Objectives This appendix provides you with reference information on the program synchronization feature. Program Synchronization Both processors in a ControlNet PLC-5 backup system execute their own program logic. You can configure the ControlNet PLC-5 backup system to have either Asynchronous program scans or Synchronous program scans. Asynchronous mode allows the program scans on the two processors to run as if they were stand-alone processors.
D-2 Program Synchronization Determining Which Mode to Use Determining whether to select Asynchronous mode or Synchronous mode depends on your application. If the program logic is completely different between the two processors, it is appropriate to select Asynchronous mode. Also, if the program scan time frequently bumps out from a small value to a very large value so that the configured Maximum Program Scan Time is too large for the application, it would be appropriate to select Asynchronous mode.
Program Synchronization D-3 Because every program scan is pushed out to the Maximum Program Scan Time, it is advantageous to configure the Maximum Program Scan Time parameter to be as close to the largest program scan time as possible. The only way to determine the largest program scan time for a particular application is to run the application in Asynchronous mode under all conditions and then determine what the largest program scan time was. You can determine this by viewing the Status File word S:9.
D-4 Program Synchronization Should frequent program scan overruns occur, it may be necessary for you to increase the Maximum Program Scan Time parameter. The Maximum Program Scan Time parameter can be changed "on-the-fly" to the primary processor while the processor is in RUN mode. Both processors will automatically begin using the new Adjusted Maximum Program Scan Time parameter.
Appendix E Application Guidelines Chapter Objectives This Appendix will provide you with application examples, as well as information on other items to consider while operating your ControlNet PLC-5 hot backup system. Redundancy Considerations The PLC-5 system for redundancy is designed to allow a secondary PLC-5 to take over I/O and system control from a primary PLC-5 which has become disabled.
E-2 Application Guidelines Switchover Considerations The following sections provide information on factors you should keep in mind when performing a switchover. Why Transfer Information? When the primary PLC-5 is operating, system outputs are a function of current and prior I/O events. Outputs may be in the present state because a current input condition requires a certain output state. If the secondary system comes online and senses the input condition, it will place its output in the same state.
Application Guidelines E-3 What Information Should Be Transferred? The secondary PLC-5 transfers selected PLC-5 memory files on qualification. Timers, counters, and PID structures contain past state information, so these critical state variables are automatically transferred. You can also select a range of files to transfer by entering the beginning file number and ending file number in the configuration parameters.
E-4 Application Guidelines If the secondary begins execution with the control register at a different point than the primary, the secondary data table may diverge from the primary since its instruction is behind the primary. IMPORTANT In a ControlNet Hot Backup system, do not attempt to crossload MG, BT or CT file types. Additionally, make sure these files are not in the range of user-defined crossload files. This could lock-up messages on the secondary PLC-5.
Application Guidelines E-5 Performance Considerations One approach to redundant system design is to transfer as much of the primary data table to the secondary as possible and as frequently as possible. This approach is not required and actually lowers the overall performance of the system. First, ControlNet bandwidth is lowered because much more unscheduled message traffic is used to transfer data.
E-6 Application Guidelines It is also important that the secondary PLC-5 remains at the same state with the primary PLC-5, or it may diverge into a different process state. When both programmable controllers remain at the same state and the primary PLC-5 faults or fails, the secondary PLC-5 would properly assume control of the sequential process in the correct process state. Not all applications follow a sequential process.
Application Guidelines E-7 Data table values can become outdated because the data table crossload is performed one at a time from low data table file number to high data table file number. The data crossloaded from the low data table file number becomes outdated while the higher number data table file numbers are crossloaded. Once the qualifying PLC-5 has transitioned into Run mode, the state data table crossload begins.
E-8 Application Guidelines How to Keep the Hot Backup Programmable Controllers in the Same Process State The design of the application is the most important factor to keeping the programmable controllers in the same state. Structure the application so that there are a low number of well-defined process states. The more states there are in an application, the more complex it becomes, thus increasing the chances that it will not take into account every event that may cause a process state transition.
Application Guidelines E-9 How to Complete Qualification in the Same Process State During qualification, the qualifying PLC-5 transitions into Run mode and begins scanning the program ladder logic.This is when the two programmable controllers are most likely to get into different process states. One approach to avoid this is to have the qualifying PLC-5 track the process state of the primary PLC-5 until the state crossload is finished. This should be done with a scheduled message every NUT.
E-10 Application Guidelines Notes Publication 1785-UM024B-EN-P - January 2003
Appendix F Comparison to the 1785-BCM System Chapter Objectives This appendix provides you with a comparison between the ControlNet PLC-5 backup system and the 1785-BCM backup system. Comparison to the BCM System Like the BCM scheme, the ControlNet PLC-5 backup system makes use of a primary and a secondary PLC-5, where both the primary and secondary PLC-5s simultaneously execute their control logic.
F-2 Comparison to the 1785-BCM System In terms of how data is provided to the two PLC-5 systems, similar to the BCM system, the ControlNet PLC-5 backup system does automatically present the ControlNet input data (both discrete and analog) to both PLC-5 processors. Unlike the BCM, however, the ControlNet PLC-5 backup system does NOT provide the remote output data (discrete and analog) to both PLC-5s.
Glossary This glossary is specific to ControlNet PLC-5 Hot Backup terms used in this manual. For a comprehensive automation glossary, see the Industrial Automation Glossary, publication AG-7.1. A active switchover Refers to a condition in which the primary PLC-5 is aware of and able to signal to the secondary PLC-5 that a switchover must occur. This occurs when the primary goes to Program mode, or when you supply a switchover command.
ii • • • • ControlNet ControlNet ControlNet ControlNet DIF and DOF files Configuration file Status file Diagnostic file Once this data table crossload is done, the secondary PLC-5 begins scanning its control program and a Phase 2 data crossload operation begins. During this phase, the accumulator elements of all timer and counter structures in the data table are copied from the primary PLC-5 into the secondary PLC-5. This transfer brings these dynamic values up-to-date in the operating secondary.
iii ControlNet network address The address on the ControlNet network given to each node (also referred to as the node address). For the PLC-5s in the hot backup system, the ControlNet network addresses must be consecutive numbers, with the lower number being odd. For example, a valid network address pair is 5 and 6. Data Highway Plus crossload A configuration option that allows you to crossload data table files over Data Highway Plus instead of ControlNet.
iv Note: When performing editing on either PLC-5, we recommend that you disable this feature first. This will avoid a situation where the secondary PLC-5 cannot be qualified because there are memory section differences between it and the primary. F forced switchover A configuration option that allows you to on demand, force transfer of control from the primary PLC-5 to the secondary and vice versa.
v N network update time (NUT) The repetitive time interval in which data can be sent on a ControlNet network. This interval represents the fixed time interval for sending scheduled and unscheduled messages from a ControlNet node. The network update time ranges from 2ms-100ms. no control backup state When a valid backup configuration exists, but the PLC-5 is not in Run mode, the PLC-5 ControlNet backup system is in the no control backup state.
vi Q qualification A phase of operation each PLC-5 goes through before being considered ready, or qualified, to take control of the system outputs. The qualification phase begins when the PLC-5 is switched into Run mode. During qualification, various checks are made to ensure that the PLC-5 is properly configured. If the secondary PLC-5 is the one going through qualification, various data is read from the primary.
vii switchover The transfer of control from the primary PLC-5 to a qualified secondary PLC-5.
viii Publication 1785-UM024B-EN-P - January 2003
Index Numerics 1747 adapter enhancements 2-4 1771 adapter enhancements 2-4 1785 firmware enhancements 2-4 1785-BCM F-1 1785-CHBM P-1 1785-CHBM/A 2-5 specifications A-1 1794 adapter enhancements 2-4 A advanced configuration options 3-18 application considerations, sequential process E-5 application guidelines E-1 asynchronous mode 3-18 asynchronous program scanning 3-20 audience of this manual P-1 B backflashing firmware 2-3 backup 1785-CHBM/A 2-5 advanced configuration options 3-18 backup states B-1 cartr
2 Index ControlNet, planning and installing P-3 ControlNet, publications P-3 ControlNet, related documentation P-3 crossload data over DH+ definition 3-18 invalid channel configuration 3-25 performing 3-24 crossloading data table C-1 definition 3-18 performing 3-22 D data table crossloading definition C-1 diagnostics C-9 effect on ControlNet channel C-9 inhibiting C-9 latency C-8 on-demand C-2 other methods C-10 qualification C-7 required time C-8 designated primary, requalification of dual primary contr
Index N new features of ControlNet Hot Backup 1 no control backup state B-3 node address settings 3-1 O objectives of this manual P-1 on-demand crossloading, disabled 3-27 on-demand crossloads optimizing C-5 triggering C-5 on-demand data table crossloading C-2 optional parameters, configuring 3-19 ordering documentation P-3 output ownership verification 4-4 P PC requirements 2-1 personal computer requirements 2-1 PLC-5 compatible firmware revisions 2-2 editing considerations 3-26 EDS files 2-2 enhancemen
4 Index switchover considerations B-16, E-2 synchronizing programs D-1 synchronous mode 3-18 synchronous program scanning 3-20 system architecture, hot backup 1-2 system requirements firmware 2-2 hardware 2-1 software 2-2 summary 2-4 system status diagnostic counters 3-23 invalid state reason 3-24 maximum pscan information 3-24 qualification error reason 3-23 viewing 3-23 T technical support 2-2 terms and conventions P-2 testing data table edits 3-27 The Automation Bookstore P-3 transitions, backup state
How Are We Doing? Your comments on our technical publications will help us serve you better in the future. Thank you for taking the time to provide us feedback. You can complete this form and mail it back to us, visit us online at www.ab.com/manuals, or email us at RADocumentComments@ra.rockwell.com Pub. Title/Type ControlNet PLC-5 Hot Backup System User Manual Cat. No. 1785-CHBM Pub. No. 1785-UM024B-EN-P Pub. Date January 2003 Part No. 957345-74 Please complete the sections below.
PLEASE FASTEN HERE (DO NOT STAPLE) PLEASE FOLD HERE NO POSTAGE NECESSARY IF MAILED IN THE UNITED STATES BUSINESS REPLY MAIL FIRST-CLASS MAIL PERMIT NO.
Publication 1785-UM024B-EN-P - January 2003 25 Supersedes Publication 1785-6.5.24 - February 1999 PN 957345-74 Copyright © 2003 Rockwell Automation, Inc. All rights reserved. Printed in the U.S.A.
