Beckhoff TS5066, Manual

Page: 14 / 31

PLC API
TS5066 14 Version: 1.0
AxisOut : Output axis structure with corrected axis set values.
3.2 FB_TimeSync
This function block is used for system synchronization. The phase difference of the systems is determined
based on the cycle index of received network variables, and a correction time is calculated.
Description
For synchronization of distributed systems the information is sent cyclically by one system and received by
the others. Phase differences between the cycle times of the sender and the respective receiver lead to beat
effects (see
introduction [ } 7] ) through information being missed or read twice. In the following section only
the case with nominally identical cycle times on the sender and receiver side is considered. For different
cycle times (even-numbered ratios are supported) the following description applies with different values.
Each send process is associated with a consecutive number, i.e. cycle index m of the network variables. The
following cases may occur for the difference Δm
i
between the cycle index received during the current cycle
(i) and the previous cycle (i-1) (Δm
i
=m
i
-m
i-1
):
Δm=0: The same data are read during the current and the previous cycle.
Δm=1: The sent data are received continuously.
Δm>=2: One or several pieces of information were not received.
Figure 1 schematically shows the case for Δm=0, i.e. duplicate reading of information, at the position
indicated. Figure 2 shows case Δm=2, with sent information being skipped and not analysed.
Fig. 7: Figure 1: Beat effect if the cycle time of the sender (S) is greater than that of the receiver (E).
Corresponding sender and transmitter cycles are linked through lines.
Fig. 8: Figure 2: Beat effect if the cycle time of the sender (S) is smaller than that of the receiver (E).