Top 3 Modbus Interview Questions
Browse 3 real-world technical and behavioral interview questions about Modbus. Review scenarios, edge cases, and architectural best practices.
You need a second system reading the same PLC data that SCADA already polls. What could that do to the line?
Answering a poll is work the controller does with the processor that runs its logic, so a second master competes with the control function rather than sitting beside it. Take the feed from the existing aggregation point, and treat the tag map as somebody else's change-controlled artefact.
A dashboard has been showing the same temperature for two days and nobody noticed. Walk the path and tell me what would have caught it.
On any protocol that reports by exception, no new value and an unchanged value look identical, so liveness has to be carried deliberately. Status codes, source timestamps, birth and death messages and a source-side counter each establish it at a different layer of the path.
Compare OPC UA, Modbus and MQTT. What is each one for, what security does each give you, and how does each fail?
Modbus is a register read/write protocol with no types and no security; OPC UA is an information model with certificate-based security and subscriptions; MQTT is a broker-based transport that says nothing about payload meaning. They sit at different layers rather than competing.