PLC Protocols

If the machine that is being connected is a Programmable Logic Controller (PLC), such as a Siemens S7, Omron, and Mitsubishi PLC, the data is collected by accessing a certain memory location. These PLCs use a variety of protocols to send and receive data. In order to successfully get the data from the PLC after it has been connected, please provide the person implementing the connections the following:

1. Machine brand and model: This allows us to understand the type of machine being monitored or controlled. 2. Preferred name for machine: This allows us to name the data source correctly. 3. IP Address: Provide the static IP address of the PLC.

4. For each variable available from the PLC, provide the ALL the following information. If this information is available from a manufacturer’s guide, then please send the guide to the person implementing the connections.

  1. Data Block name. For Siemens S7 it should be something like "DB" or "FC7"

  2. Memory location where the value exists. This must be in a specific format depending on type:

    1. Boolean values: eg; MX13.1. The value M is ignored, but the X denotes a bit wise mapping. 13 is the memory location, and .1 is bit 1.

    2. Date and Integer values: eg; MW2. The value M is ignored, but the W denotes a WORD (2 byte) entry. 2 is the memory location, in this case.

    3. Real (decimal) values: eg freal334. The value freal is used to denote a real (4 bytes value). 334 is the memory location, in this case.

  3. Name of the variable (e.g: Grid Voltage)

  4. Units of the variable (e.g: Volts)

  5. Scale of the variable (e.g: must be divided by 100 to get Volts)

  6. Read only or Read/Write. Whether the variable is Read Only (RO) or Read/Write (RW)

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