Allen Bradley PLC Interview Questions and Answers

Allen Bradley PLC Interview Questions and Answers : This article covers industrial automation interview questions and answers which covers basically AB PLC related questions and answers

Allen Bradley PLC

Allen Bradley PLC Interview Questions & Answers

Programmable Logic Controller – Allen Bradley

What are the PLC ranges available in Rockwell?

  1. Pico : Non modular small PLCs
  2. Micrologix 1000, 1200 and 1500 Series
  3. SLC : SLC 5/01, 5/02, 5/03
  4. Control Logix Flex Logic and Soft PLC

What are the software Used with AB?

  • For Pico soft for Pico PLC programming
  • RS Logix 500 for Micrologix and SLC PLCs programming
  • RS Logix 5000 for Control Logix PLCs programming
  • SCADA – RS View earlier Control View

What is use of RS Linx software?

RS Linx software is used to perform following tasks.

  • Configure communication drivers
  • View configured drivers and active nodes
  • Enable communication tasks such as uploading, downloading, going online, updating firmware and sending messages.

What is use of RS Logix software?

RS Logix is a PLC programming software. It contains all the instructions needed for PLC programming.

We can develop the program, down load / upload the program, work on line / off line and force the I/Os using the software.

  • RS Logix 500 is used for Micrologix and SLCs
  • RS Logix 5000 is used for Control Logix PLCs

What file gets created in PC for RS Logix PLC program?

The extension of the file will be .rss. So if you create an application with “Demo” name the file created will be “Demo.rss”.

By default it will be stored in “c:\Program Files\RockwellSoftware/RS Logix 500 Eng location.

How to creating linkage between PLCs and PLC programming software?

The RS Linx software is used for linking the PLC and software Either you can manually configuration the communication settings or By using Auto Configure facility the software will detect the communication settings automatically.

Hardware configuration (PLC and I/Os)

  1. Manual configuration
  2. Auto detect

What is the meaning of Upload and Download?

  • Upload means transferring the program data from PLC to PC
  • Download means transferring the program data from PC to PLC

What are the various communication interfaces supported by AB?

The commonly used communication protocol in AB includes DH+, DH485, ETH, Modbus, Device Net and Control Net.

Give information about DH, Control Net, DeviceNet and Ethernet protocol.

Data Highway:

The proprietary data network used by Allen Bradley PLCs to communicate information to and from other PLCs on the network or to and from host computers attached to the network.


A real-time, control-layer network providing high-speed transport of both time- critical IO data and messaging data, including upload/download of programming and configuration data and peer-to-peer messaging, on a single physical media link


A low-cost communication link that connects industrial devices to a network. It is based on broadcast-oriented communication protocol – the Controller Area Network (CAN).


The standard for local communications networks developed jointly by Digital Equipment Corp., Xerox, and Intel. Ethernet base band coaxial cable transmits data at speeds up to 10 megabits per second.

Ethernet is used as the underlying transport vehicle by several upper-level protocols, including TCP/IP.

What is latency in communication?

The delay time between the end of one communication and the start of another.

During this time, the processes associated with the communication are hung up and cannot continue. The latency has to be minimum.

How the communication protocols are distinguished?

The protocols are distinguished with following specifications

No. of nodes supported, total network length , Speed of communication .

Comparison between various Protocols used with AB

various Protocols used with AB PLC

Is Allen Bradley Rockwell?

AllenBradley is the brand-name of a line of Factory Automation Equipment manufactured by Rockwell Automation (NYSE ROK).

What is RSLogix?

The RSLogix™ family of IEC-1131-compliant ladder logic programming packages helps you maximize performance, save project development time, and improve productivity.

Who owns Rockwell Automation?

Rockwell Automation traces its history to 1903 and the formation of the Compression Rheostat Company, founded by Lynde Bradley and Dr. Stanton Allen with an initial investment of $1000. In 1904, 19-year-old Harry Bradley joined his brother in the business.

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