Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Compare Modbus, Fieldbus, and Profibus
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Control Systems > Compare Modbus, Fieldbus, and Profibus

Compare Modbus, Fieldbus, and Profibus

Last updated: September 28, 2022 2:40 pm
R Jagan Mohan Rao
Control Systems PLC Tutorials
2 Comments
Share
7 Min Read
SHARE

Modbus is a granddaddy of industrial communication protocols. Modbus is Modicon plus fieldbus.

Contents
Modbus RTU:Modbus ASCII:Modbus TCP/IP:ModbusProfibusProfibus DPProfibus PAFoundation FieldbusFoundation Fieldbus H1Foundation Fieldbus HSECompare Modbus, Fieldbus, and Profibus

Modbus, a serial communication protocol developed by Modicon in 1979. It is developed by  Modicon for PLC in industrial applications, now it an open protocol. It is used over serial and Ethernet cable.

It is easy to implement and also easy to use. The term Modbus typically refers to one of three variants.

  1. Modbus ASCII.
  2. Modbus RTU
  3. Modbus TCP/IP.

Modbus RTU:

This is used in serial communication. Makes use of compact, binary representation of data for protocol communication.

Modbus ASCII:

This is used in serial communication, makes use of ASCII characters for protocol communication.

Modbus TCP/IP:

This is used for communication over TCP/IP networks.

Modbus is often used to connect the supervisory computer with an RTU in the SCADA system.

Modbus

Modbus RTU is the most popular protocol, use three physical media.

  • RS 232,
  • RS 485,
  • RS422.

Point to Point Communication

RS 232 is a point to point communication. One device to one device can be connected and the distance between two devices is 50 feet (15 meters) then RS 232 does the job.

Modbus Point to Point Communication

Multidrop Communication

To connect more devices on the same line, and have a distance greater than 50 feet, one can use RS 485, or RS422. This standard supports 32 nodes over 4000 feet( roughly 1200 meters).

Modbus Multidrop Communication

With Repeaters

Modbus is a simple Master/Slave protocol. With one being the master all are slaves only. Maximum of 32 slaves without repeaters on RS 485 physical medium.

With repeaters, 247 slaves can be connected as shown in the below figure.

Modbus with Repeater

They answer only when a master’s talk to them. If the master doesn’t talk they keep idle. There is also no requirement for diagnostic information on the slave’s health.

Modbus ASCII and RTU use physical layer RS232 or RS 485. A device configured in ASCII mode can not be used in RTU. Both are not compatible with each other.

Daisy Chain Network

Modbus and PROFIBUS are protocols built on RS 485, they used daisy chain architecture for connection.

Modbus daisy chain topology

RS 232 is a point to point communication,

RS 485 or RS 422 is for multidrop applications. 

Profibus

PROFIBUS is a young athlete, lean and fast. As with the Modbus, there are a number of variants associated with Profibus.

  • PROFIBUS PA,
  • PROFIBUS DP,
  • PROFIBUS FM
  • PROFINET,
  • PROFISAFE.

Profibus ( Process Fieldbus) is one of the standards for field bus communication in automation technology. 

PROFIBUS is also a Master/Slave protocol. But with additional token ring protocol to allow multiple masters as shown in the figure below.

PROFIBUS has certain protocol features that let certain versions of it operate in multi-master on RS 485 which Modbus could be the only a single master.

PROFIBUS is also a Master Slave protocol

Profibus DP

PROFIBUS DP (DP-Decentralized Peripherals) is used in machine automation and other discrete signal applications.

The main physical layer for PROFIBUS DP is RS485.

PROFIBUS DP

Profibus PA

PROFIBUS PA (PA- Process automation) is used in process control applications. It connects to PLC by Profibus-DP through a segment coupler as shown in the figure below.

PROFIBUS-PA devices are not directly accessible by PROFIBUS master, the segment coupler allows intrinsic connection to electrically isolate PA devices from DP network.

PROFIBUS PA

Foundation Fieldbus

Foundation Fieldbus: The idea behind field bus is to eliminate any point to point links between the field devices like transmitter, control valves and their controllers by a single digital connection.

Foundation Fieldbus technology is mostly used in process industries and power plants.

There are two variants.

Foundation Fieldbus H1

Foundation Fieldbus H1 is a bidirectional communication protocol with 3125 Kbits/S speed.

It utilizes twisted pair cable to connect field devices to the controller.

Foundation Fieldbus

Foundation Fieldbus HSE

Foundation Fieldbus HSE. It utilizes Ethernet media to operate at 100/1000 Mbit for connecting gateways, host systems. Both FF H1 and FF HSE use different physical media and at different speeds.

Foundation field bus was designed to address the needs of real-time process automation. FF was conceptually engineered as a replacement of the normal analog 4-20 mA current loop.

Foundation filed bus is not only a communication protocol but it is a language form for building control strategies.

FF is a peer to peer protocol. Field instruments such as transmitters can communicate with each other without a host e.g. A DCS or a PLC and they can initiate communication without a specific hos command.

The control functionality can be in the field devices or in the host (PLC or DCS) or partially in both.

When control functionality is within the field devices, without halting the loop, the host can be disconnected.

Also Read: HART Protocol versus Fieldbus

FF has a number of advantages making it a leading protocol for communicating field devices in digital closed-loop control.

For example, the separation between real-time and non-real time communications so that device management tasks do not interfere with closed-loop control.

Compare Modbus, Fieldbus, and Profibus

Data Rate of Modbus, Fieldbus, Profibus
Communication of Modbus, Fieldbus, Profibus
Compare Modbus, Fieldbus, Profibus
Difference between Modbus, Fieldbus, Profibus

If you liked this article, then please subscribe to our YouTube Channel for PLC and SCADA video tutorials.

You can also follow us on Facebook and Twitter to receive daily updates.

Read Next:

  • What is Fieldbus?
  • Automation Protocols
  • What is HART Protocol?
  • OSI Layers of Communication
  • SCADA Communication
  • Basic Industrial Networks
Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Basics of Motion Controllers
PLC Instruction List for Motor Reverse and Forward Direction
Comparison of Proportional Integral Derivative Controllers (PID)
Two Hand Press Safety Control Circuit
Parking Lights PLC Program Explained with Video
PLC Programming for Weight-Based Packaging
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
2 Comments
  • P Maruthi Prasad says:
    June 4, 2020 at 8:26 pm

    Superb explanation i ever read.

    Reply
  • Ramahari Mahapatra,9937021976 says:
    January 22, 2022 at 7:06 pm

    There is a requirement of Fieldbus, Module No PDP22-FBP-500
    DC505 Connector Profibus DP/VI
    Please suggest where to get. Any Contact No. Mailid . Please suggest.

    Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Basics of Alarms and Trips
DCS
Pressure Control Loop Wiring Connections
Rockwell PLCs for Large Scale Applications
DCS Troubleshooting Control Valve Loop
PLC Program for Paint Spraying
Why Use a Current Loop?
Integrating Processes – Liquid Level Control

Keep Learning

PLC Documents

PLC System Documentation

Industrial Automation Cold and Hot Standby

Difference between Cold Standby and Hot Standby

PC-Based Motion Controller

Various Types of Delta PLC used in Industrial Automation

PID Controller Gains Effect on Setpoint

PID Controller Gains Effect on Manipulated Variable

Parts of PLC

Parts of PLC

Complementary Split Range Control

What is Complementary Split Range Control (CSRC)?

What is an RTU - Remote Terminal Unit

What is an RTU? – Remote Terminal Unit

Basics of PID Controllers

PID Controllers in Closed Loop Control Systems – PLC Basics

Learn More

PLC Program for Car Parking

PLC Program for Entry and Exit Control of Car Parking

repairs of welding cast refractory lined box over the hot spots

Too often done riskily repaired Roof Hot Spots eliminated forever

Relay ladder diagram example

How to Draw a Schematic Diagram ?

SCADA Interview Questions

SCADA Interview Questions and Answers

Optical Modulation

What is Optical Modulation? – Methods of Optical Modulation

Cavitation Test Setup

Cavitation Test Setup

Wet Contacts and Dry Contacts in PLC Systems

Wet Contacts and Dry Contacts in PLC Systems

Inductors in parallel

Series and Parallel Inductors

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?