BECKHOFF EtherCAT Technology Section I - Manual (Page 87)

Distributed Clocks
Slave Controller – Technology I-67
The second option uses a SyncSignal output of ESC 1 to trigger Latch0 at ESC 2 and an interrupt at
the µController. Upon receiving an interrupt, the µController writes the time of the SyncSignal pulse to
the System Time register of ESC 2. The µController has to calculate the time of the SyncSignal based
upon Start Time Cyclic Operation and SYNC Cycle Time configuration of ESC 1 from interrupt to
interrupt. The advantage of the second solution is less communication, the disadvantages are more
calculation overhead and error detection/troubleshooting.
ESC 1
DC source
S
y
n
c
0
IRQ
ESC 1 generates SyncPulse
for ESC 2 and IRQ for µC
µC writes Sync time of ESC 1
(calculated by µC) to System
Time register of ESC 2
1
2
µController
ESC 2
DC
destination
L
a
tc
h
0
Figure 33: System Time PDI Controlled with two steps