Why TSync(Time Synchronization) is needed in Adaptive AUTOSAR?

Question

I'm a rookie in Adaptive AUTOSAR.

I can't imagine why Time Synchronization(Tysnc) is needed. System time of ECUs can be synchronized by PTP.

Could you explain why Tsync is needed even though PTP synchronize time across a distributed system? Or I welcome any documents or materials for me to understand Tsync's usages or use-cases.

Answer 1

The reason for the existence time sync along with the definition of time domains is that you need to be able to define different time domains across different bus systems within the vehicle. One example for a not directly obvious definition of a time domain could be the metering of operation-hours.

On top of that, the time domains can cross AUTOSAR platforms, i.e. a time domain may consists of both CP and AP nodes.

You can find explanations for time sync in (e.g) the AUTOSAR documents TPS Manifest and TPS System Template.

Answer 2

There need to be different time bases in vehicle. Examples of Time Bases in vehicles are:

• Absolute, which is based on a GPS based time.
• Relative, which represents the accumulated overall operating time of a vehicle, i.e. this Time Base does not start with a value of zero whenever the vehicle starts operating.
• Relative, starting at zero when the ECU begins its operation.