What is PROFIBUS: DP and PA

PROFIBUS DP for factory automation and PA for process instrumentation: masters and slaves, DP-V0/V1/V2, GSD files and where PROFIBUS is still used.

Two flavours

	PROFIBUS DP	PROFIBUS PA
Use	Remote I/O, drives, factory automation	Process transmitters and valves, hazardous areas
Physical layer	RS-485 (copper) or fibre	MBP (IEC 61158-2), 31.25 kbit/s, power and data on two wires
Speed	9.6 kbit/s … 12 Mbit/s	31.25 kbit/s
Connection to DP	—	DP/PA coupler or link

PA devices are powered over the bus and can be intrinsically safe; a coupler converts between DP and the MBP segment.

Masters and slaves

Class 1 master (DPM1) — the PLC: exchanges cyclic I/O data with its slaves.
Class 2 master (DPM2) — engineering / diagnostic tool, temporary access.
Slaves — I/O stations, drives, transmitters. A slave answers only when polled.

Several masters share the bus by passing a token; each master polls only its own slaves.

Protocol versions

Version	Adds
DP-V0	Cyclic data exchange, standard diagnostics
DP-V1	Acyclic read/write of records (parameters), alarms — needed for PA and drive parameters
DP-V2	Isochronous mode, slave-to-slave (data exchange broadcast), clock synchronization

GSD files

Every slave type has a GSD text file (extensions .gsd, language variants .gse, .gsg…) describing supported baud rates, modules, parameters and diagnostics. The master is configured with these files; the bus address set on the device (rotary switch or software) must match the project.

Status today

PROFIBUS is no longer the choice for new factory-automation designs (PROFINET took over), but huge installed bases remain, and PA is still common in process plants. Knowing how to troubleshoot RS-485 segments is a daily skill — see physical layer and troubleshooting.

Connections

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Sources

PROFIBUS — technology overview — PROFIBUS & PROFINET International (PI)
SIMATIC NET PROFIBUS Network Manual, 04/2009 — Siemens AG

Updated 2026-10-02