#18 PLC Best Practices – Store PLC Hard Stop Events from Faults
Store PLC hard stop events from faults or shutdowns for retrieval by HMI alarm systems to consult before PLC restarts.
Store PLC hard stop events from faults or shutdowns for retrieval by HMI alarm systems to consult before PLC restarts.
Log PLC uptime to know when it’s been restarted. Trend and log uptime on the HMI for diagnostics.
Summarize PLC cycle time every 2 to 3 seconds and report to HMI for visualization on a graph using trend.
Define safe states for the process in case of PLC restarts (e.g., energize contacts, de-energize, keep the previous state).
Restrict the type of PLC connections and available data for third-party data interfaces in a programmable logic controller,
Disable unused communication ports and protocols that are not required in PLC controllers and network interface modules.
Ensure operators can only input what’s practical or physically feasible in the process. Learn the PLC’s best rules.
Instrument the process in a way that allows for plausibility checks by cross-checking different measurements.
Assign designated register blocks for specific PLC functions in order to validate data and block unauthorized access to controller data.
PLC best practices – Validate indirections by poisoning array ends to catch fence-post errors.