Lika SFA-10000-EC, Руководство пользователя, Страница: 53 / 84

SFA-5000 • SFA-10000 EtherCAT
6.1.6 Communication mode
Lika encoders with EtherCAT interface support the following operating modes:

FreeRun: asynchronous mode;

SM3 event: synchronous mode;

DC: distributed clock synchronization mode (synchronous mode).
For a system that requires high performances in real time (closed-loop
applications) we suggest using DC mode; if real time requirements are not so
mandatory SM3 or FreeRun modes can be used instead.
A reference parameter is the “Jitter”: it represents the temporal fluctuation of
the instant data sampling; in other words data sampled by the micro-controller
is available in ECAT DPRAM memory after a certain time and the measure of the
variability over time is the “jitter”.
FreeRun
Asynchronous mode; the encoder position is sampled directly from EtherCAT
frame sent by the Master; the position update is performed by an internal timer
of the controller every 100 microseconds.
This operating mode has a high sampling jitter (up to 100 microseconds) and
can be chosen only when cycle times are quite longer than the jitter if we want
to ensure a sufficient real-time system performance.
Description Min Typ Max
Jitter 0 100 µsec
Cycle Time 1000 64000 µsec
See the
1C33 SM input parameter
entry on page 66.
MAN SFA_5000_10000_EC E 1.0.odt 6 - EtherCAT® interface 53 of 84
0x1C33:02 (Cycle Time)
0x1C33:06
(Calc & Copy)
Local Timer Local Timer
Input Latch
Local
Timer
Local
Timer
Local
Timer
Local
Timer
Local
Timer
Local
Timer
Frame N Frame N+1