36 lines
1.0 KiB
Markdown
36 lines
1.0 KiB
Markdown
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# Supervisory Control and Data Acquisition (SCADA)
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* SCADA works as an aggregatio of the following systems
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* __Programmable Logic Controllers (PLC)__, monitoring sensors and controlling devices.
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* __Remote Terminal Unit (RTU)__, use for wide area telemetry
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* __Human Machine Interface (HMI)__, supervisory through an operator. Interaction through human user input.
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* __Communication network__
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* Security is no first class citizen
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## Modbus
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* Developed by Modicon
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* Master/Slave, latter has an 8 bit address.
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* RS-485 Connector
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* Data registers 16 bit
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* Input register, 16 bit ro
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* Hold register, rw
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* Coil register, 1 bit rw
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* Discrete register, 1bit ro
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### Function Codes
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* [Modbus101](https://www.csimn.com/CSI_pages/Modbus101.html)
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* RTU request inside of TCP segments, port 502
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* 1 __Read Coil__
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* 2 __Read Discrete Input__
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* 3 __Read Holding Registers__
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* 4 __Read Input Registers__
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* 5 __Write Single Coil__
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* 6 __Write Single Holding Register__
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* 15 __Write Multiple Coils__
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* 16 __Write Multiple Holding Registers__
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