Tuesday, March 6, 2012

Omron PLC Interface





If you are weary using some complex non-real-time components of COM/COM+ that pressure you to join the Omron PLC series and are concerned in an simple understanding, actual real-time, open source .NET based on the object, this article explains a simply code-based the protocol Host link implementation, what you can simply add into your project makes sure you a safe consistent the PLC communication-RS232/485 PC.

Programming OOP and using a precise realization in real-time hardware charge is something it has done once in the Controller of DeltaDTB PID.

1. Wiring
The mainly confusing subject one may look with no doubt, after reading the file of PDF decreased from Omron telling the attributes of Host Link, is substantial connection that is cable wiring. After first perusing, they made some connecting hoping it would run, but there was no success regardless of all the efforts.

2. Communication Protocol
Host Computer
In the host link communication protocol, the host computer has the priority transition, but for the case of connection peer to peer noting this issue is not very vital, but if you’re very scrupulous and sensitive about, because definition of Omron. The data transfer between the Host Link System and the host computer is, consequently, initiated when the computer transfers a control to a PC in the System of Host Link. The PC, which operates the application, understood as Host Computer.

• Block
A data set in a transmission is called a block.

• Command Block
The block data transferred from the host computer to the System of Host Link is called a block of command.

• Response Block
The block transferred from the System of Host Link to the computer is defined as a response block.

• Single Link Communication VS Multiplex Communication
Each block begins with a header and a unit number, and ends with a FCS (Frame Checksum) code and a terminator (* and CR) in a system of the multiple-link communications. However, every block begins with only a header, and finishes with only a terminator in a single-link system.

• Termination
The terminator in the command block allows the PC to transfer a response. The terminator in the reaction block allows the host computer to transfer another command.

Block Formation
A data block is typically made up of one of the unit defined as a frame, but the long data blocks must be separated into more than one frame before communication. In a system of multiple-link, the initial frame can contain up to 131 characters, and consequent frames can contain up to 128 characters.

However, each frame contains up to 128 characters in a single-link system. The data have to then be separated into more than a frame when there is a block comprising of more than 131 characters in a system of multiple-link and of extra than 128 characters in a system of single-link. In this matter, the starting and intermediate blocks end with a delimiter (CR), as a substitute of a terminator (* CR).


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