Faster HMI updates from edge runtimes

Previously, edge runtimes batched variable updates to connected HMIs on a fixed 250 ms interval. Edge runtimes now use on-change notifications: as soon as a watched variable changes value in the PLC scan, the new value is pushed to the HMI immediately.

The result is sub-scan-cycle responsiveness on operator screens for buttons, indicator lamps, alarms, and live process values, with no configuration required.

What you will notice

• Indicator lamps and alarms react in the same cycle as the PLC, instead of with a perceptible delay.
• Live process values (temperatures, speeds, counts) update as fast as the PLC writes them.
• Network and CPU usage drop when values are stable — no traffic is sent if nothing changed.

Where this applies

• All edge runtimes running this release or newer.
• HMI projects deployed to those edge devices.

Note

Cloud-hosted (non-edge) runtimes continue to use the existing update strategy. The on-change behavior described here is specific to edge runtimes where the HMI shares the device with the PLC.

Caution

On-change updates make the HMI more sensitive to noisy analogue inputs. If a value updates many times per second because of sensor noise, apply a filter or deadband in the PLC logic before mapping it to the HMI tag — otherwise the screen will flicker.