https://control.com/technical-articles/introduction-to-modbus/
In 1979, Modicon introduced a new protocol leveraging the application layer of the OSI model specifically for use with its PLCs. This protocol was called Modbus and became the first widely used fieldbus in the history of automation.
https://control.com/technical-articles/introduction-to-modbus-and-modbus-function-codes/
Created in 1979 by Modicon (now Schneider Electric), Modbus was originally used to communicate with the Modicon family of PLCs. Today, Modbus is an open protocol used by PLC and automation device manufacturers.
https://control.com/textbook/digital-data-acquisition-and-networks/modbus/
Developed by the Modicon company ... in its industrial control products, Modbus is a protocol designed specifically for exchanging process data between industrial control devices....
https://control.com/forums/threads/i-am-new-to-modbus-looking-for-guidance.49808/
The protocol you referred to as Modbus RS-485 could be either Modbus RTU or Modbus ASCII. Modbus RTU is much more common than ASCII. That's one of the things you have to establish, is which protocol is in use?
https://control.com/forums/threads/modbus-protocol-guide-and-examples.17787/
I'm looking for some examples about applications developed with Visual Basic 6. I will develop an application working on ethernet (tcp-ip) and so I have been starting studying something about protocol. I need to know more about it. Where can I find something about OCX for using in Visual Basic environment? Thank you. ... Hi, You will get a good examples for DLLS and OCX's in MSDN and MODBUS protocol guide from http://www.modbus-ida.org.
https://control.com/forums/threads/modicon-modbus-protocol-guide-pi-mbus-300-rtu-crc-calculation-description-correction.50921/
The LSB that is extracted (shifted out) is a 1. In addition, please note that the PI-MBUS-300 spec you're referring to is over 25 years old (from 1996) and is obsolete. Although the CRC description is identical in the latest spec (Modbus Serial Line Protocol and Implementation Guide V1.02).
https://control.com/forums/forums/modbus.36/
A community for the Modbus communications protocol - data communication between devices over TCP/IP and over serial line – open and royalty-free since 1979. Visit Modbus.org to download the Modbus protocol specification and implementation guides.
https://control.com/forums/threads/modbus-protocol-vs-tcp-http-protocol.36493/
Modbus is a very common industrial protocol that comes in several forms: 1) Modbus/RTU and Modbus/ASCII - These are normally delivered over RS-232 or RS-485. There is no transport protocol involved here, and Modbus has to take care of any delivery ...
https://control.com/forums/threads/interfacing-with-modbus-protocol-using-pc.39901/
You are correct Steve. In the strict definition of Modbus there can be only one master BUT you can extend that definition to be "one master at a time" and that opens a door to multiple Modbus Masters communicating with the same slave(s) and does not "break" the protocol.
https://control.com/technical-articles/tls-transport-layer-security-protocol-secure-modbus-TCP/
Security comes with added protocol complexity. Many industrial control systems rely upon encapsulating Modbus Application Protocol (MBAP) Protocol Data Unit (PDU) messages carried on a TCP/IP network within a “TLS” layer to secure communications.
https://control.com/forums/threads/modbus-com-protocol-mixed-up-confusion.51987/
The 200-PEU seems to be a device made by Intuicom that is meant to replace the end-of-life FGR2-PE-U (https://www.intuicom.com/serial-ethernet/200-peu/freewave-transition/) Now, generally speaking, if these radios are taking Ethernet packets and converting them to radio signals then back again, Modbus need not be supported, only the underlying TCP protocol (since Modbus/TCP runs on top of TCP).
https://control.com/forums/threads/modbus-protocol-and-solving-issues-using-it.44833/
So bottom line, Modbus require YOU to know what the device it, then find a paper/PDF document from the manufacturer which explains that (for example) data number #73 must be divided by 320, then multiplied by 100.0 to produce a power "amperage" reading. Literally, if you do NOT have a manual, you CANNOT use a Modbus device effectively.
https://control.com/technical-articles/choosing-an-interface-why-modbus-is-still-around-after-40-years/
Modbus is an open serial protocol based on a multi-drop client/server architecture. In a typical Modbus network, one server communicates with up to 247 clients using either a 2-wire topology or a 4-wire topology in accordance with EIA/TIA-485 ...
https://control.com/forums/threads/modbus-ascii-protocol-standard-definition-or-net-library.55321/
Modbus ASCII is a serial-only protocol defined in the Modbus specifications. The other defined serial protocol in the specifications is Modbus RTU, which uses binary encoding instead of ASCII, and is the more commonly used of the two.
https://control.com/forums/threads/connect-many-devices-in-a-modbus-protocol.31117/
Modbus can be used with devices connected in a bus configuration, and is generally implemented with an RS-485 physical connection. So, in your application, you would need to convert your devices to RS-485. Another option may be Ethernet, using a Modbus gateway, which can connect RS-232/422/485 serial devices to Ethernet, and convert between ASCII or RTU and the TCP protocols.
https://control.com/forums/threads/modbus-over-ethernet.29872/
The Modbus protocol has now been "ported" to Ethernet, and it's called Modbus/TCP. There are some minor differences, like the fact that you've now got binary data instead of ASCII text, and you don't need the CRC check that the serial version had. (Actually, just to complicate things further there's Modbus/RTU, which is the binary-over-serial version of Modbus.
https://control.com/forums/threads/file-transfer-using-modbus-protocol.17909/
These registers are then read and, usually, a index register is written by the master telling the device to load the registers with the next data set. The process then repeats untill all the data sets are read. If the device is ModbusTCPIP based its easier to use TFTP to retieve the file.
https://control.com/forums/threads/modbus-protocol.24745/
No need. Modbus is part of Modbus plus as the name suggests. Just communicate using Modbus protocol.
https://control.com/forums/threads/advanced-hidden-modbus-protocol.20067/
Modbus ASCII, RTU and TCP are open protocols. The instruction set includes read and write instructions. It's up to the device manufacturer to supply the the specifics of the implementation of the registers, addressing and the associated word ...
https://control.com/forums/threads/modbustcp-application-develop.40651/
Write via Modbus protocol to %Mxx and then move to %Qxx (DOUT) Move %IWxx (AIN) to %MWxz for reading via Modbus protocol Unlocated variables and system bits/words must be moved to located references (%M or %MW) in the controller for remote access. Use the MOVE function.
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