Modbus server vs application server
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Don’t expect to see Modbus in use between computers in the office to share information that usually doesn’t match that list above. Modbus is superior in its simplicity, short messages, and direct interaction with control devices like PLCs, and simple, integer-based network devices like VFDs and HMIs. Writing to (also reading from) register outputs Reading register inputs (like analog inputs, integer calculations, or motor control values for example) Writing to (also reading from) boolean outputs The actual data is limited to just a couple of possible types of commands: The most dynamic info in the header is the length of the data - it tells the receiver how much information it’s about to send. This header is 7 bytes (56 bits) which is relatively short and simple. Modbus defines a header of information that tells the receiving device what data to expect. Once again, this part of the protocol is the same between all TCP/IP networks so that they may work alongside each other and never cause problematic data collisions and conflicts.įinally, we reach the part of the communication which is different and specific to every module being used.
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The other piece, the Transmission Control Protocol (TCP), is the part that establishes what action should take to prevent data collision, and what should happen if an error does occur.
#Modbus server vs application server Pc#
Since these are globally standardized, proper addressing allows these devices to work right alongside any laptop or PC connected to the network switch. Many documents can be found which explain IP addresses, subnet masks, gateways, and server addresses. The Internet Protocol, which defines the addresses, are required to get to the proper network and device.
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This part of the network specification includes two pieces, the Internet Protocol (IP) and the Transmission Control Protocol (TCP), which is why the networks are listed as TCP/IP. This category is also the same between the Modbus and Profinet network types. Speed is usually 100 Megabit per second or 1 Gigabit per second on modern “gigabit’ switches. The transmission speeds are limited by the devices on each end and the network switches. It usually looks like a side-by-side locking hole in the communication module with an optical transmitter and receiver hidden inside. Some equipment is switching to fiber-optic connections due to speed and electrical noise immunity, and the connector is slightly different. It appears in nearly all modern industrial processor-based equipment, although again, sometimes requires an add-on module.Ī subtle but critical difference in the physical connectors - the larger 8-pin RJ45 at the top is for the Ethernet TCP/IP connection, but the smaller 6-pin RJ12 at the bottom is for the Modbus connection. The connector is quite recognizable as a square plastic plug with eight metal contacts and a locking tab. This means that any related protocol, including Modbus TCP/IP and Profinet, will be precisely the same in the area of physical specs. This part of the network is identical between Modbus and Profinet, and any other network relying on internet transmission and addressing protocols.Įthernet is the physical standard that limits what types of connectors, wires, voltages, and speeds may be allowed to ensure compatibility. This includes the common term ‘Ethernet’ which is common in home and industrial networks. Industrial networking relies on coordination between three different parts of the communication message, the physical and transmission standards, and the application data - two of these are identical between Modbus and Profinet, the last one is where the difference occurs. Many end devices, such as this VFD, require an adapter (the blue device) to take the application data of normal Modbus and wrap it up in the physical and transmission standards of Ethernet TCP/IP. If you work in a facility with cables sharing data between PLCs, motor drive units, HMIs, remote I/O distribution blocks, and most likely PCs, then you probably need to understand some of the basic network principles. Still, there must be some differences, or there would be no reason to purchase different communication modules. Two of the most common are Modbus and Profinet - they can appear similar in many ways. Regardless of the physical method, we must understand how the various protocols differ in order to build effective networks. Sometimes, communication ports are built right into the front of the processor modules, while other times is an add-on card or module. Industrial computer networking is the ability to allow data to be transferred between all of the devices in the facility with processors.