In PROFIBUS DP, device-related diagnostics is an asynchronous vendor-specific message that the slave emits to report internal conditions (temperature alarm, low battery, etc.) which go beyond the standard diagnostic block.

Device-related diagnostics carries the vendor's internal alarms: the format is defined by the manufacturer inside the GSD (Diag_Text entries), the codes are proprietary and not standardised across vendors, and they are decoded through vendor-specific tooling (TIA Portal for Siemens, equivalent suites for ABB, Endress+Hauser, etc.). Typical messages include "Sensor calibration due in 30 days", "Internal memory error" or "Backup battery low". Reading the device datasheet is mandatory to interpret the codes correctly.

Always keep the GSD and the device manual side by side during commissioning: a device-related diagnostic byte means nothing without the vendor's decoding table.