Glossary · System coordination, integration and orchestration
Handshake
Also known as: handshaking, request-acknowledge exchange
German: Handshake
In automation and communication, a handshake is an exchange of signals or messages between two systems in which each step is confirmed by the partner before the next step begins, so that both sides stay synchronized.
- System integration
In one sentence
A handshake is an exchange of signals in which each step is confirmed by the partner before the next begins, keeping both sides in step.
Example
The PLC sets Request, the robot answers with Acknowledge, the PLC resets Request and the robot resets Acknowledge, which completes one four-phase handshake.
How it applies
- Engineering: A full (four-phase) handshake confirms both the setting and the resetting of signals and is robust against cycle-time differences. Shorter variants save time but can lose or duplicate requests when partners scan at different rates.
- Commissioning: Test handshakes with interruptions at every step: power loss, communication loss and manual reset of one partner.
- Documentation: A timing diagram with the signal names used in the PLC programs is the clearest documentation of a handshake. Troubleshooting guides should explain how to find out at which step a handshake is stuck.
Handshake vs. heartbeat
A handshake synchronizes a specific exchange. A Heartbeat only shows that the partner is alive and communicating; it carries no request or confirmation of a task.