OPTO 22 SNAP PAC Redundancy Option, User Manual

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CHAPTER 4: CREATING A STRATEGY WITH CONTROLLER REDUNDANCY
SNAP PAC Redundancy Option User’s Guide
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definition above) within the logic. A transactional chart is usually sequential; it starts at one block
and proceeds sequentially through command blocks to the end using variables, inputs, and outputs.
Creating a Redundant Strategy
When you create a strategy for controller redundancy, most tasks such as configuring I/O,
programming with commands, using PID loops and so on are exactly the same as for a
non-redundant strategy. (See form 1700, the
PAC Control User’s Guide , for more information on
creating a strategy in PAC Control.)
What makes a redundant strategy different is:
• A redundant control engine
• Persistent/redundant variables
• One or more transactional charts, which use sync blocks to organize logic into transactions
In order to create a strategy to run on redundant controllers, you must first configure
persistent/redundant variables that you want to be replicated to the backup controller. Then you
create transactional charts, using sync blocks to indicate where in the logic you want the
synchronizations to occur.
Creating a PAC Control strategy for controller redundancy includes the following tasks.
“Step 1. Enabling the PAC Control Redundancy Features” on page 33
.
“Step 2. Adding a Redundant Control Engine to a PAC Control Strategy” on page 36 .
“Step 3. Configuring Persistent/Redundant Data” on page 39 .
“Step 4. Designing a Transactional Chart” on page 41 .
Step 1. Enabling the PAC Control Redundancy Features
When redundancy is enabled for a strategy, the following features become available:
• The Sync Block icon appears in the toolbar. If you do not see the sync block icon, click in
the logic area of a chart to make it appear. For information on using sync blocks in a
strategy, see
Chapter 4: Creating a Strategy with Controller Redundancy .
Sync block tool
• PAC Redundancy Manager can be accessed within PAC Control for control engines configured
for controller redundancy. You can also access PAC Redundancy Manager from the Start menu:
select Start
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Programs

Opto 22
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PAC Project Software

PAC Redundancy Manager. For
instructions on using Redundancy Manager, see “Step 2. Adding a Redundant Control Engine to
a PAC Control Strategy” on page 36 and sections in Chapter 3 and Chapter 5 .