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What Is Modbus TCP/IP ?

The Modbus TCP/IP, or Modbus-TCP is similar to the Modbus RTU protocol, but with a TCP interface that runs on Ethernet. The Modbus messaging structure is an application protocol that rules the organization and interpretation of data independently of the data transmission medium.

TCP refers to the Transmission Control Protocol, while IP refers to Internet Protocol. These two protocols are the transmission medium for the Modbus TCP/IP messaging. Essentially, the Modbus TCP/IP exchanges blocks of binary data between computers. This protocol is also considered to be a world wide standard and provides a foundation for the World Wide Web. The TCP is to ensure all the packets of data are received correctly, with the IP ensuring that the messages are addressed and routed correctly. This TCP/IP combination is the transport protocol, it is the Modbus application protocol that defines what the data means, and how it is interpreted.

To summarize, the Modbus TCP/IP uses Ethernet and TCP/IP to transport Modbus message structure data between compatible devices. What this means, in essence, is that it combines the physical network of the Ethernet, with the TCP/IP networking standard and the Modbus application protocol as a standard of data representation. So, it is a Modbus communication with an Ethernet TCP/IP wrapper.

The Modbus and user data are contained in a TCP/IP telegram, but are not modified at all. The Modbus error checking field, checksum, isn’t used. The standard Ethernet TCP/IP layer checksum methods are utilized instead to guarantee the integrity of the data. The Modbus frame address field is replaced by the unit identifier in Modbus TCP/IP, and is part of the Modbus application protocol header.

If you are in need of Modbus Gateways please see our product line here


Application Guidelines

When configuring a DH+ link for your system it’s important to consider the following application guidelines.

  • To achieve acceptable response times, you will need to minimize the number of DH+ nodes. It’s important when minimizing DH+ nodes to keep frequency and size of the messages exchanged between devices in mind.
  • To achieve the fastest control response time possible, you’ll need to limit the number of stations on your overall network. To bring on additional stations, establish separate DH+ networks.
  • Never remove or add stations to the network during process or machine operation. If the network token is situated with the removed device, it can be lost to the rest of the network. Automatic re-establishment of the network could take several seconds to activate. During this time, control is interrupted or unreliable.
  • Try to avoid programming controllers as much as possible online during process or machine operation. This could increase response time by possible long bursts in DH+ activity.
  • Add a separate DH+ link where possible for processor programming to keep the effect of programmed terminals from the process DH+ link.



What Is Industrial Automation Engineering Technology?

With the increase in demand for industries to manufacture and produce top quality products, it’s important that the technology and industrial automation services behind the company is sound to ensure smooth operation of the business each and every time. Automation engineering technology is used by many industries to produce an abundance of items ready for market and resale, amongst other things. But what exactly is automation engineering technology you ask? The following is a brief guide to what this technology is so you can be more informed.

industrial automation servicesWhat Is Industrial Automation Engineering Technology?

Automation engineering technology is the term that’s used for a variety of systems which include process controls and communications. Technicians in the industrial automation engineering field generally combine key fundamental principles of mechanical engineering technology with electronic and electrical circuits to develop, design, test, and manufacture computer controlled and electrical mechanical systems which are becoming a key foundation element in industrial industries.

The industry of automation is a branch of the electronics field and is fast becoming one of the major growing areas of international and national high technology economies. Industrial automation engineering technology features a combination of electronics, mechanics, and electrical, and includes the control or interaction of computers, motors, hydraulics, pneumatics, and other processes which are applied and used within manufacturing.

What Do Automation Engineering Technicians Do?

Industrial Automation engineering technicians use theories and principles of engineering, science, and mathematics to come up with solutions to technical problems in areas of development, research, inspection, construction, manufacturing, and maintenance. More practically orientated than most engineers and scientists, automation engineering technicians general assist in the research and development process of ordinary scientists and engineers.

The areas where automation engineering technology is used includes in quality control environments. This means the inspection of processes and products, along with the process of collecting data and conducting test.  In the area of manufacturing, technology is used to help with the product development and design, along with the production process. Programmable logic controllers or PLCs are a significant area where automation engineering technology is used. This involves conducting work with special-purpose computers to create synchronization of the different technologies which are used within the manufacturing process. Automation engineers who are familiar with PLCs generally setup and use the special-purpose computers.


Automation engineering technology plays a major role in many businesses and industries. If you’re a business that requires an automation engineering technician it’s best to check their credentials and ask them questions about what they can help you with to make sure you find the right technician to suit your individual needs.


What differences exist between Modbus and Modbus Plus?

Understanding the differences between Modbus and Modbus Plus are very important. Modbus is based on the RS232C serial standard communications that define the cabling, connector pinouts, signal levels, parity checking, and transmission baud rates. It’s a master slave protocol that uses the Modicon controllers through a common language.

Modbus Plus, is a network protocol that uses high speeds between the networks of peer connections. Upon the receipt of the token frame, Modbus Plus nodes on the access of the network. When the node hold a token, it can start transactions with several devices on the same network.


What is Modbus Communication Basics?

Developed in 1979, Modbus industrial serial protocol makes communication between automation devices possible. It is used with programmable logic controllers or PLCs. It transmits the information over serial lines that exist between electronic devices. The Modbus Master requests the information and the device that supplies the information are the Modbus Slaves. In a standard network, there are up to 247 slaves and one master. Each of the slaves have their own unique addresses. The master has the ability to write information the each of the slaves. The slave device has to wait to be asked for information and cannot give it without permission. The master writes the data to a slave devices registers and also reads the data from the registers.

What Modbus is used for?

This common protocol is used by many devices for efficient, reliable, and simple over many of the modern networks. A giant server can be used as the master for a PLC and then the PLC can be used as a valve, motor, sensor, or other device that is embedded. It is now the standard in the industry when it comes to communications protocol and the most available way to connect industrial electronic devices. Many manufacturer’s use it in various industries. It is mostly used to give off signals from control devices and instrumentation back to system gathering data or main controller. An example could be a system that tells the humidity or temperature back to a computer. A remote terminal unit or RTU within a supervisory control and data acquisition or SCADA system can be connected to a Modbus.

Modbus/TCP can make the definition of slave and master less obvious. That is because the Ethernet can allow for a communication system that works as a peer to peer connection. The client and the server are better known in Ethernet-based networking. When this happens, the slave can become the server and the master can become the client. That allows for more than one client to obtain data from the server. That way there is a chance of having multiple masters and multiple slaves. It allows for a system where the slave and the master are not defined on a physical device.

How does Modbus work?

Serial lines transmit the Modbus between devices. In a simple setup, there is a single serial cable that is connected to two serial posts, the master and the slave. Then the data is sent in bits, which are a series of ones and zeros. They are sent as a voltage. The zeros are positive volts and the ones are negative volts. These bits very quickly sent at a speed of 9600 bits per second called a baud.

Popular terms to know

When dealing with a Modbus communication protocol, you will want to know some popular terms. They will help you understand the concepts better.

  • Hexadecimal: Every block of eight bits which is called a byte. It can be represented by pairs of 256 characters from 00 to FF. Long strings of zeros and ones can be difficult to read. The bits are shown and combined in hexadecimal. Each of the block of four bits are represented by one of the sixteen characters ranging from 0 to F.
  • ASCII: It stands for American Standard Code for Information Interchange. Every eight bits can be represented and combined by one of the 256 ASCII characters just like every 4 bits can be represented and combined by one of the sixteen hexadecimal characters from zero to F.

How is the data stored in a Standard Modbus?

The information is stored in four tables in the slave devices. Two of these tables store the on and off values or coils and two store the numerical values or registers. The registers and coils have a read-write table and a read-only table.

  • Every table has 9999 values
  • Every contact or coil is one bit. Plus, it is assigned an address between 0000 and 270E
  • Every register is one word that equals 16 bits which equals two bytes. They have a data address between 0000 and 270E.
  • Coil and register numbers are thought of as location names that do not appear in the message.

What is a Slave ID?

Every slave in the network gets a unique unit address that is between 1 and 247. When there is data requested from the master, the slave address is the first byte that is sent. The reason why it does that is to tell the master whether to ignore the message or not.

What is the function code?

The master sends the second byte as the function code. It is the number that tells the slave what table to access and if it should write to or read from the table.

What is a Cyclic Redundancy Check or CRC?

The two bytes that are added at the end of the Modbus message designed for error detection. All of the bytes in the message are used to calculate the CRC. The device that is receiving the message calculates the CRC and then it compares it to the sending device’s CRC. It is used for protection. If even one part of the message is incorrectly received, the CRC is different and then the error will result.

What is word and byte ordering?

The way the data is stored in the registers is not defined with the Modbus specification. So, some manufactures have implemented Modbus into their equipment that stores and transmits a higher byte first and then a lower byte next. Other devices transmit and store the lower byte first.

The technology is forever changing and improving. The new methods make it easier for communication between master and slave.

Huge Trends that Affect Industrial Automation

With each new era, there comes new IT issues and manufacturing trends to deal with. The most popular topics that have been featured in many manufacturing publications include:

  • The Internet of Things
  • Big Data
  • Cloud Computing

These trending topics involve devices that are networked together and have a lot of data available to do things. Also, they include a decision on whether the applications are accessed and the data is stored on a server or your computer.

However, there are supporting technologies that work behind them all that have already been developed. Here is what you need to know about each of these topics to manage through them.

industrial automation gateways

  1. The Internet of Things or Connected Industrial Devices

The Internet of Things involves a lot of devices that are industrial that are networked together. This could be plants with thousands of devices that are networked together.

Reasons to network:

  • Everything can be managed from anywhere
  • Reduced hardware costs and complexity because of a the one network
  • Information and control can be moved when needed

The whole point of the Internet of Things is to connect industrial devices to each other so that the connectivity can be used to improve business.

DSC05809Challenges to network:

  • Learning and understanding the new technology
  • Deciding how to design the systems

With the development of this concept, the vendors and groups that set standards will take care of the difficult parts. The evolution of the technology will handle the growth as more wireless ports are added. Security will be upgraded helping with the management of higher traffic levels. Then, more IP addresses are created finalizing the process of continuing the business environment prior to the growth. Plus, your company has to encourage the use of this innovative technology.



  1. Big Data

When data sets are incredibly complex and large that the regular applications for data processing are inadequate, this is referred to as Big Data. There is a lot of information that can be used for many different things, but isn’t being used. New software is now used that can analyze the large amounts of data, so that it can be used. Web companies and search engines use this type of technology. The systems measure, record, and interpret the information. For example, Amazon, makes suggestions to their customers about what to buy based on the information that is gathered from past purchases and items that the customers put in their cart. They make suggestions for repeat purchases and send notifications when the price on items that are saved in their cart changes. This is done to initiate a response from the customer to buy some more cologne or buy the tablet that just dropped in price.

Once a company learns how to utilize the data, they are able to build their business and offer more products that the consumers will want.

Connected-Green-Cloud3.Cloud Computing

Cloud computing deals with the computation and storage of your data on another source and not on your computer. Today, the computing power isn’t completely viable for use in an industrial capacity. However, the storage capacity is very strong. It provides a great way to share your data and back up your files.

Gateways can also segment networks into logical segments. They can allow for a clear division for different parts of the facility. If there is a need to optimize performance or maximize availability, the portal’s division can be useful.Industrial gateways allow you to optimize your network whenever your goal is to redesign, configure, or extend an industrial network.



Modbus is a messaging protocol that defines the content of that message.

In a short time hundreds of vendors implemented the Modbus messaging system in their devices and Modbus became the de facto standard for industrial communication networks.

Communication between the Modbus nodes was achieved with messages. It was an open standard that described the messaging structure. domain map The physical layer of the Modbus interface was free to choose.

The original Modbus interface ran on RS232, but most later Modbus implementations used RS485 because it allowed longer distances, higher speeds and the possibility of a true multi-drop network. RS485 is hardware serial-interface standard that defines the hardware for carrying a message.

If you need more info on MODBUS check this manual out!

DL3500 General Operation & Applications

DL3500 General Operation & Applications

The DL3500 continues the functionality of the DL2000/DL3000 product line. It offers both the new addition of DH485 as well as a plug and play USB interface. As well as having the DH+ and 232/422/485 capabilities of the DL3000. Two DL3500 Models will also allow Bridging between DH+ and DH485networks. New is the ability to power the DL3500 from the USB communication link, removing the sometimes cumbersome procedure of location an AC or DC power supply when using laptops or PC’s inthe field.

The DL3500 has two communication ports. Channel A is designed to connect to you industrial network,either AB DH+ or DH485 networks. Channel B is used to connect to your serial or USB device, the protocol depends on which flavour (model) of the DL3500 you have ordered.

Channel B has the capabilities of RS232C, RS422, RS485 and USB 2.0. Configuration of the operating parameters is done quickly and easily by the DL32 V3.X windows based software shipped with the unit or available on the Equustek Website. Currently there are three standard DL3500 products available to allow access to A-B’s DH-485 and DH+ network.

Many other custom ASCII and serial protocols have been implemented to Both DH+ and DH-485 on the DL3500 platform. Contact Equustek Solutions to see if the DL3500 is the correct device for your communication needs.

The DL3500 has all three models below available in DH+ and DH485 flavours:

The DL3500-Modbus is a two port device that bridges your Modicon Modbus devices to ones on an Allen Bradley DH485 or DH+ network. The Modbus model can either be used as Modbus Master or Modbus Slave as well as having both Modbus ASCII and RTU protocols.

The DL3500-DF1 is a two port device that allows your DF1 devices (either Full or Half Duplex protocols) to ones on an Allen Bradley DH485 or Allen Bradley DH+ network. The DF1 model is a direct replacement for the 1770-KF3 for DH-485 and 1770-KF2 for DH+ and allows your PCs or Laptops access to any node on the corresponding A-B network.

The DL3500-ASCII interfaces Serial ASCII devices (Scanners/Printers) to SLC’s or other devices on an Allen Bradley DH485 or DH+ network. The DL3500-DF1/DH+ or DH485 interfaces your DF1 devices (either Full or Half Duplex protocols) to ones on either an AB DH485 or DH+ network. The DL3500 comes with both networks available with only using the software configuration program to switch between the DH485 and DH+ networks


Ethernet/ip to dh+

Equustek produces Ethernet/ip to dh+ protocol converters and network gateways

Lots of people are asking the question, “why go with the Ethernet/IP gateway to DH+ instead of updating all my Allen Bradley Equipment such as PLC5s to Ethernet/ip ?”

There is an excellent answer to this, The Ethernet/IP gateway to DH+ has supplied a solution to many of our problems, it has created existence a hell of a lot simpler for (A-B) Allen Bradley PLC(programmable logic controller) consumers as it has enabled them to never want the possibility to upgrade all their Allen Bradley software and equipment. Imagine never needing to upgrade the equipment again, no more spending cash every time time an update occurs, Thanks to Ethernet/IP gateway to DH +, you need to fork this money out, as you’ll be taken good care of for good.

The total cost of the ethernet/ip dh+ is also cheap, you can actually save your self a good amount of cash. If you use ethernet/ip dh+ converters, you do not have to upgrade each PLC with an Ethernet processor . The Ethernet/IP gateway is as easy as things can get. What you have to realize is the fact that you will never have to to update each PLC with an Ethernet processor.

Industrial Ethernet Systems

Industrial Ethernet Gateways

Ethernet TCP/ip address timing’s unknown nature has for ages been a downside for most professional system programs, especially people that have realtime ability demands that are strict. However, as the total price vs. gain efficiency has enhanced over time, commercial consumers are suffering from strategies to beat the evident short-comings.


As a whole, there are now about thirty commercial Ethernet techniques in use all over the world, but these most critical to the us marketplace are:

  • Ethernet/IP
  • Modbus/TCP
  • EtherCAT®
  • Ethernet Powerlink
  • Profinet

Every one of these methods have already been developed together with the problems of realtime handle in head (routine times, low-latency, low that was steady) the plan of preventive steps to prevent data collisions, plus the option was contacted by them in manners that were various.

The one noticeable distinction to the regular TCP/internet protocol address method is the enactment of real-time Info trade segments that are further on the top or that manage real time communication-either in location.

However, all methods carry on assistance for the Ethernet (IEEE 802.3) real and data layers and TCP/ip address/UDP, therefore supplying an interface to normal advice stage sites.

Methods like Modbus and Ethernet/IP /TCP seem to function as the most vulnerable in terms of realtime management that is difficult, since they inherited most of the characteristics that leave Ethernet TCP/ ip address low -deterministic. While the CSMA/CD dilemma ( arbitrary delay instances after coach settlement ) may be somewhat suppressed through the application of Ethernet changes, these practices nevertheless have to cope with the further jitter brought on by UDP and ip address. Without careful layout thoughts, they are going to not be unquestionable for motion control applications that are speedy, especially for challenging real time management.


Ethernet Powerlink circumvents the CSMA problem quite stylishly through circumventing the TCP/ip address/UDP levels as it pertains to communicating that is real time. Exceptionally deterministic and committed time-slices put to every node in the community are utilized by Ethernet Powerlink. The effect is while other nodes wait for his or her change, the fact that just one node carries data to the coach all through its time cut that is committed. This process therefore removes arbitrary and efficiently prevents any information crash dwell times. Clearly, the ip address jitter is additionally eliminated by the circumventing of TCP/IP/UDP.


EtherCAT nevertheless, approached by removing it totally in the real level, which, in most effect, demands the application of a dedicated equipment the CD difficulty. While an (registered company) grasp method needs merely a standard Ethernet network software, each (registered company) device takes a control that is committed. EtherCAT(registered company) nevertheless uses Ethernet as the physical level, Nevertheless, the Ethernet communications are passed from node to (daisychain), so getting rid of the requirement for bus settlement per CSMA/c d.


Profinet, when compared with any or all other practices released here, has experienced a transition through all previously detailed situations: Profinet V-1 (CBA) uses the common Ethernet TCP/IP, Profinet V-2 (RT) circumvents the TCP/ip address/UDP levels, while Profinet V3 (IRT) utilises a dedicated Ethernet control.






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