Category Archives: Modbus TCP

ACC Automation 2016 Review

Acc Automation

We would like to take a few minutes and reflect on the past, current and future of ACC Automation. You have help us succeed in our best year yet.

Starting off we learned how to:
Create a PLC with HMI Training and Learning Environment Free – Utilized the Do-More Designer Software and the AdvancedHMI Software we communicated Modbus TCP to the Do-More simulator. This was all done on one computer without any need for additional hardware. The best thing about this was that the investment was only time learning the packages. Continue Reading!

The 7 Essential Parts of a PLC System

When I was in school PLC’s were just in their infancy. We were taught that the PLC consisted of the central processing unit (CPU), analog and digital inputs and outputs. Everything was programmed with dedicated handheld devices and/or software devices on specialized hardware. We now have modern PLC systems that are capable of so much more. Let’s look at how we can now break up these modern PLC system into the seven essential components.

Inputs and Outputs (I/O)
Analog I/O
Specialty I/O
Programming Tools
Networking Continue Reading…

Horner XL4 System Hardware

The Horner XL4 OCS is an All-in-one controller. This means that this modern unit combines a logic controller, operator interface, I/O and networking all into one package. This OCS (Operator Control Station) family was first released in 1998. New features to the line-up have been added over the years. Today the OCS family has a very competitive advantage as you will soon see.
Programming is done with a single programming software package. Cscape (Control Station Central Application Programming Environment) is designed to be easy to use and maintain.

This series on the Horner XL4 all-in-one controller (PLC) will go step by step through learning how to use this innovative unit. Continue Reading…

Click PLC AdvancedHMI Communication

Advanced HMI is a powerful, adaptable HMI/SCADA (Supervisory Control and Data Acquisition) development package that takes advantage of Visual Studio. There is no coding required and you can simply drag and drop items onto the page. The best thing is that the software is free. We will look at using AdvancedHMI with the Click PLC. Our sample Click PLC program will read the present value (PV) and the indicating lights on our Solo Process Temperature Controller. It will then write the set value (SV) to the Solo. This communication will be done using Modbus RTU protocol over a RS485 serial port on the Click. The AdvancedHMI package will communicate Modbus TCP over Ethernet to the Click PLC. We will be able to monitor our PV and set our SV on the Solo via the AdvancedHMI window.  Keep on Reading!

Click PLC Send and Receive Instructions

Receive and Send instructions will allow you to send and receive serial data to an external device. The communication method that you setup can be ASCII or Modbus. ASCII (American Standard Communication for Information Interchange) can be used to send to devices such as a printer. Receiving ASCII can be used for connecting barcode scanners to the PLC. The barcode will be read as an ASCII string in the PLC. Modbus serial communication (Modbus RTU) is a standard protocol used in many automation devices. We will demonstrate the Send and Receive instruction by communicating Modbus to a Solo Temperature Controller. Our example will read the current process (PV) value and write the set point value (SV) in the controller.  Keep on Reading!

Click PLC Timers and Counters

Continuing our series, we will now look at timers and counters and how they are used in the Click PLC. Previously we have discussed:
Click PLC System Hardware
Click PLC Installing the Software
Click PLC Establish Communication
Click PLC Numbering System and Addressing
The programming software and manuals can be downloaded from the Automation Direct website free of charge.  Keep on Reading!

Click PLC System Hardware

Many people ask me what I do when looking at a new PLC model or system. My approach is very straight forward and we will view this in action with this Click PLC series. This series will go from examining the hardware to programming and communicating to the PLC in several ways. If you have questions along the way, please let me know. Keep on Reading!

What Everybody Ought to Know About IP Addressing

Communication using Ethernet usually evolves around the Open Systems Interconnection model (OSI model). This model was made for computing systems to communicate without regard for the underlying internal structure and technology.

Think of it like sending a letter:
You write the message on paper – This is like the protocol that the system will be using. The protocol is like the language that the two devices will be communicating.

Sign it at the bottom of the paper – This signature is like a MAC address for the system. It will uniquely identify you.

Put it into an envelope and address it (Also return address) – This address is like the IP address for the system. It lets everyone know the location that the letter is going and returning.

Stamp, and put it in the mail – This is like the physical cable that we will be using. The schedule pickup, sorting, routing etc. to get you letter to the sender is now out of your hands.
This is similar to the OSI model. The layers within the model will communicate with each other to ensure that the information will get to the designation without error.

IP Address:
An IP (Internet Protocol) Address is a user defined numeric label assigned to a device on an Ethernet network that identifies the network and node. An IP address is a 32 bit address that is normally grouped into 4 bytes for ease of communication and understanding. Example:
You can look up your current address by going to the following url:

MAC Address:
The MAC (Media Access Control) Address is also called the physical address. This is part of the unique identification on an Ethernet network. The MAC address is a 48 bit address that is normally grouped into 6 bytes for ease of communication and understanding. Example: 00:02:A1:BC:72:33
Here is a URL link to find your MAC address on your computer:
Devices use their hardware addresses to communicate with each other within the OSI model.

Ethernet networks support many different types of protocols, including TCP/IP. In the industrial environment you will often here of EtherNet/IP , Modbus TCP, Profinet etc. are all part of TCP/IP.

There are a defined number of IP addresses that have been defined as private IP addresses. These addresses are not allocated to any specific organization and anyone can use these without approval. Choose the one with the range that will fit your application.

Class Private IP Addresses
A –
B –
C –

Subnet Mask:
A subnet mask is an address that enables distinction between networks. It is used to divide the network into smaller units called Subnets. This is beneficial when the office communications are separate from the plant floor communications. It adds level of security and enhances maintenance and upgrade options.
A subnet mask is a 32 bit address that is normally grouped into 4 bytes. This is the same as the IP address, because we compare the IP addresses with the subnet mask to determine if they can communicate directly with one another. If not then the communication must happen through a router to get to the destination. The subnet mask must match for communications to happen.

Compare the following Modbus TCP addresses and see if they are on the same subnet:
Modbus TCP Address 1:
Modbus TCP Address 2:
Subnet Mask:

Convert these decimal values to their binary equivalent:
(You can do this by using your windows calculator in programmer mode. View | Programmer or Alt + 3)

Modbus TCP Address 1:
Modbus TCP Address 2:
Subnet Mask:
Same Subnet Compare:
If the subnet mask has a ‘1’ then compare the two addresses and see if they are similar. In our example there is a difference, so the two devices will not communicate. You must change the subnet mask on the entire system or IP address.

Let’s now change the IP address on Address 2.
Modbus TCP Address 1:
Modbus TCP Address 2:
Subnet Mask:

Convert these decimal values to their binary equivalent:
Modbus TCP Address 1:
Modbus TCP Address 2:
Subnet Mask:
Same Subnet Compare:
We can now communicate successfully.

Troubleshooting your Ethernet network is easy by using a free product called Wireshark.
This software will monitor and display your Ethernet traffic. Highlighting different communication protocols, you can quickly see your communication in action. Introduction to Wireshark Video gives a good overview of what is possible and shows what to look for on your network.

IP Address selection on your network must be unique. You cannot have two addresses the same. As a general rule only those addresses within the same subnet will communicate to each other without the need for a router.

Watch on YouTube : What Everybody Ought to Know About IP Addressing
If you have any questions or need further information please contact me.
Thank you,

If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

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