Data & Communications
A PLC has a wealth of information inside. Information such as math calculations or input
state of a device are stored in PLC's data area. Data areas are internal memory registers
of a PLC, each with it's own memory address. These data are accessible from external
systems via communication ports built in a PLC. Usually, a PLC will have a 9-Pin serial
RS232 port with Modbus included as one of the communications protocols. Optionally,
they may have Ethernet ports or various filed buses such DeviceNet or Profibus. Example:
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