PDA Software (Plant Design & Allocation)

PDA software (Plant Design & Allocation) can be used in the control system design stage and is useful in delivering plant wiring and termination diagrams. PDA software can be used in conjunction with ABB Control Builder to simplify coding tasks. Its functionality includes defining:

• Control structure
• Process objects (can be imported from Excel Sheet)
• Signals (can be imported from Excel Sheet)
• Signal lib (ready, availability, local start/stop, local/remote, etc.)
• Assigning signal lib to process objects and generating signals
• Allocating signals to the physical channels
• Assigning process objects to the signals
• Assigning CAD library (ELCAD) by ASCII files
• Generating circuit diagrams

The multiuser functionality of PDA saves time and effort by providing access to its database for the engineering team simultaneously.

Remote IO Configuration (Profibus) vs. Direct IO Connection (Module Bus)

Various I/O systems can be connected to the AC 800M controller, either directly (S800 I/O) or via PROFIBUS. S800 I/O is a distributed and modular I/O system that communicates with controllers over PROFIBUS-DP (remote) or via Module Bus (direct).

It is recommended not to use the Module Bus for connecting I/Os to the AC 800M controller. The Module Bus I/O scanning is controlled by the main processor (CPU) of the PLC, which increases CPU load and I/O scan time. In addition, using the Module Bus may impose restrictions on controller placement in the control panel. Remote I/O systems offer greater flexibility, and it is recommended to limit the maximum number of I/O stations to 15 per controller for efficiency.

Control Module vs. Function Blocks

The IEC 61131-3 standard does not fully support object-oriented programming. However, some vendors, like ABB, extend their systems with additional functionality. ABB’s “Control Builder Professional” includes an extension called control modules.

Control modules are executed based on optimal data flow determined by the compiler and run only once per scan. This execution method minimizes program errors due to incorrect order execution, making control modules more efficient than traditional function blocks.

Definition of “Structure” in ABB 800xA Core System

Structures in ABB 800xA core systems are graphical representations of the relationships between objects. Objects can be part of multiple structures, which are viewable in the Plant Explorer for easy access and management of object relations.

OPC Server / MMS Server

OPC (Object Linking and Embedding for Process Control) servers in ABB 800xA act as connectivity servers, interfacing between controllers and the core system (Aspect Server). OPC functionalities include data access, alarm and event time stamping, and historical data access. The server supports up to 60,000 variables per second.

MMS (Manufacturing Message Specification) servers handle communication between controllers and facilitate application program downloads via Control Builder. MMS serves as an intermediary layer between the OPC server and controllers.

Quota Memory

Quota memory is required by the controller during warm restarts. It must be larger than the size occupied by the application program to avoid any interruptions in code execution during downloads.

Variable Attributes

In the 800xA control system, variable attributes include:

• No attribute: The variable gets its initial value after each restart.
• Retain: The last value is retained during a warm restart but reset during a cold restart.
• Cold retain: The last value is retained for both warm and cold restarts.
• Hidden: The variable is hidden from OPC and cannot be an OPC variable.

Application Programming

When programming an application in the 800xA ABB control system (using Control Builder), it is recommended to create a new library in the “Library” section. This method allows code modifications to be made without directly impacting the main application, minimizing PLC downtime.

Master/Slave Definition in ABB Control Network

In ABB 800xA, the master/slave concept is only used for time synchronization. The master device synchronizes other nodes in the control network, while the concept differs in PROFIBUS.

IO Allocation

• Maintain existing IO allocations in migration projects.
• Do not allocate standby equipment IOs in the same IO system.
• Avoid mixing voltage levels within the same board.
• Group signals from the same multi-core cable together.

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