Datalogic AMT58 Series Manual page 143

AMT58x-EC EtherCAT®
The field for addressing is 32 bits long; there are three kinds of
addressing:
 Auto Increment Addressing = Position Addressing: 16 bits
indicates the physical position of the Slave inside the network
while 16 bits are scheduled for local memory addressing; when
the Slave receives the frame then it increments the position
address and the Slave receiving address 0 is the addressed
device;
 Fixed Addressing = 16 bits indicates the physical address of the
Slave inside the network while 16 bits are scheduled for
addressing the local memory;
 Logical Address = the Slave is not provided with its own individual
address, but it can read and write data in a section of the total
memory space available (4 Gigabytes).
6.1.6 Communication mode
Datalogic 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".
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