Technical data

Fundamentals

2.7 Time synchronization in PCS 7 - mode of operation

Time synchronization (V7.1)

Function Manual, 03/2009, A5E01216578-01

Function of the cooperative time master

The following process is initiated at the startup of a PC station that is configured as a

cooperative time master. A time message frame must be received within the wait time once

the PC station has powered up. The wait time amounts to four times the set synchronization

interval.

Possible response of cooperative time masters within the phase until the wait time has

expired:

● A cooperative time master that receives a time message frame from a different time

master within the wait time becomes a time slave.

● A cooperative time master that has not received a time message frame on expiry of the

wait time sends time message frames as the time master.

Within the set synchronization interval, all cooperative time masters check whether time

message frames have been received from the active time master on a cyclical basis. The

first cooperative master that detects three missing time message frames in succession

assumes the time master function. This ensures that only one time master exists.

Synchronization response

All time slaves and cooperative time masters on the terminal bus synchronize their internal

clock with the time message frames received. The time is synchronized as follows:

● Deviation ± 5 s:

Delay/acceleration of the internal clock

● Deviation > 5 s:

Immediate conversion (possible errors: Data packets sent off prior to the change will have

more recent time stamps than those sent off later)