PROFIsafe

showstack / protocols / profisafe

Functional safety carried over an ordinary PROFINET or PROFIBUS network. The trick is the black channel: the safety layer adds its own sequence numbers, timeouts, identifiers and CRC on top of whatever the network does, so the network itself never has to be safety-rated. Corruption, loss, delay, repetition and misdirection of a safety message are all detected by the layer above.

Machinery and motionPaid specPROFIBUS & PROFINET InternationalReported

Control Small, urgent, must arrive

Small messages that either repeat constantly or fire once. Bandwidth is almost never the problem.

What kills it. Latency and loss on the messages that fire once. A repeating level survives a dropped packet; a GO does not.

The four flows, and why the model is worth having →

What goes wrong

The black channel means the network needs no safety rating — and the watchdog timeout still becomes part of the total stopping time, which becomes millimetres of safety distance.

A safety address is configured per device and a duplicated one is a commissioning fault that has to be found before anybody relies on it.

It carries the safety function. It does not carry the responsibility: the assessment is still ISO 13849-1 or IEC 62061 across the whole chain.

Typical use

Emergency stop, guard monitoring and safe motion on stage machinery
Carrying a safety function across the same cable as ordinary control data
Safe torque off and safely limited speed commands to a drive

Sources

PROFIsafe — PROFIBUS & PROFINET International primary

Understand the mechanism

Hoists and the safety chain

Something wrong, or missing?

Known gaps on this entry: default_ports, implementations. If you can source one of them, that is a ten minute pull request.

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