BECKHOFF EtherCAT Technology Section I - Manual (Page 81)

Distributed Clocks
Slave Controller – Technology I-61
9.2.3 SyncSignal Generation
The DC Cyclic Unit / Sync Unit supports the generation of a base SyncSignal SYNC0 and a
dependent SyncSignal SYNC1. The SyncSignals can both be used internally and externally of the
ESC. SyncSignals can be generated at a specific System Time. Four operation modes are supported:
cyclic generation, single shot, cyclic acknowledge, and single shot acknowledge mode. The
acknowledged modes are typically used for interrupt generation. The interrupts have to be
acknowledged by a µController.
SYNC0
Acknowlege
SYNC0
SYNC0
Single shot
Cyclic generation
Cyclic Acknowledge mode
Activation SYNC0 Cycle Time
Acknowlege
SYNC0
Single shot Acknowledge mode
Start Time
Pulse Length of
SyncSignals
Figure 30: SyncSignal Generation Modes
The SyncSignal operation mode is selected by the configuration of the Pulse Length and the SYNC0
Cycle Time, according to the following table:
Table 32: SyncSignal Generation Mode Selection
Pulse Length of SYNC
Signals (0x0982:0x0983)
SYNC0 Cycle Time (0x09A0:0x09A3)
> 0 = 0
> 0 Cyclic Generation Single Shot
= 0 Cyclic Acknowledge Single Shot Acknowledge
The cycle time of the SYNC0 signal is configured in the SYNC0 Cycle Time register (0x09A0:0x09A3),
the start time is set in the Start Time Cyclic Operation register (0x0990:0x0997). After the Sync Unit is
activated and the output of the SYNC0/1 signals is enabled (DC Activation register 0x0981), the Sync
Unit waits until the start time is reached and generates the first SYNC0 pulse.
Some ESCs support additional activation options like auto-activation when the Start Time is written, or
64 bit extension if only 32 bit of the Start Time is written. Other options are to detect invalid Start
Times and provide debug output of SyncSignals.
Internally, the SyncSignals are generated with an update rate of 100 MHz (10 ns update cycle). The
jitter of the internal SyncSignal generation in comparison to the System Time is 12 ns.