Issues regarding the communication connection
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I have always been interested in learning about the various communication connection hardware used in DCS and PLC systems, as well as the software drivers required for them, such as RS232. I was wondering if experts out there could provide some guidance? Thank you in advance!
For DCS and PLCs, the commonly used connections are: serial ports (RS485, RS232) or Ethernet. Communication protocol: Modbus. Most modern PLCs support Modbus.
For this, you just need to look at the manual and the product routines, and then make modifications based on those routines. When it comes to taking the device apart, there’s actually not much in terms of technology involved. If you want to delve into the underlying details, then look into the corresponding communication bus standards and protocols. It depends on which level your work is carried out at. PLCs used to be equipped with 232 (and/or 422, 485 interfaces) almost always; back then, 232 was primarily used for downloading programming from a PC to the PLC. There are also many with various fieldbus interfaces (though most fieldbus devices are relatively expensive), as well as those with Ethernet interfaces. If a PC is used as a regular monitoring interface, an Ethernet connection is usually sufficient to meet the requirements, and the costs associated with procurement, development, and maintenance are not high.
For OPC communication and the like, we will use OPC communication here
It seems that ProfiBus DP is still the most widely used at present; many DCS and PLC systems support it, and the instruments in common use today also come equipped with this interface. In Siemens products, the DP method can also be used to communicate with the HMI interface. The most commonly used protocol is still TCP/IP, as it has low hardware costs, is simple to implement and operate, and is favored by both developers and users.