CyberCertPrepOT Security FundamentalsOT Fundamentals: Network Architecture & ProtocolsEASYFree question
An engineer reads the device map for a pump skid and needs to pull holding register values from the PLC. Which Modbus function code does that?
- A.Code 01 returns coil states packed into single bits
- B.Code 04 returns input register values from the plant field sensors
- C.Code 06 returns a diagnostic counter dump from the target unit
- D.Code 03 returns holding register values read from the device
Why D is correct
Function code 3 reads holding registers. Code 1 reads coils, code 4 reads input registers, and code 6 writes a single holding register rather than returning a diagnostic dump.
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