Baumer ATD - Manual (Page 25)

EtherCAT 25/42 Baumer Thalheim GmbH & Co. KG
2011-10-04/rnik Eschwege, Germany
Asynchronous Timing
In Asynchronous (Free Run) mode the encoder position data will be sampled asynchronous to the ECAT
frame. In this mode the encoder data sampling frequency (fs) is about 11 kHz. The position data sample
point may have a typical total jitter of 92µs.
The following diagram shows the relationship between data read accesses to DPRAM (from the master point
of view) at the ECAT controller and data sample and update to DPRAM from the slave (encoder).
Frame n Frame n+1
t
Data sampling
process at slave
fs
Cylce time
(PLC Task)
Cyclic read
by master
Picture 9 Non sync (Free Run) timing diagram for a multi turn encoder
At Operating temperature = 20°C, State = OP
Name Min Typ Max
Jitter (J) 0 100 µs
Cycle Time (sfc = 0/1) 1.000 64.000 µs
Table 29 Free Run timing specification for ST and MT devices
In free run mode the minimum cycle time should be larger than the maximum jitter, else the data jitter to cy-
cle time relation is poor for usual RT requirements.