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Introduction to Sercos interface
Advantages
Applications Types
Sercos III
Sercos I and II
Fiber Optics
ASICs
Timing & Interface
Sercos IDNs
I/O Functions
Cycle Times
Cyclic Operation
System Safety
Packaging Profile
Sercos Standardization
Timing

Timing is critical in serial networks because motion controls cannot accurately reconstruct the state of the machine unless everything is precisely synchronized measurements, transmissions and replies. Many of the messages that controls and drives send each other are for timing and synchronization. Methods are specified to keep the jitter on the serial link down to a low level, then an internal timing sequence is used to ensure that all drives in a loop act upon their command signal at the exact same moment, and all acquire their feedback information at the exact same moment. The result is transparent to the user.

Interface Placement

The Sercos automation bus supports position, velocity and torque mode control, which maintains technology independence between drives and motion controls. The power stage interface, controlling commutation/phase current, is not supported. A power stage interface is highly hardware dependent, requiring the vendor to design motion controls around specific motors, limiting the use of the control to that type of motor. It also involves transmitting high-speed commutation signals over long distances with microsecond update rates. Thus the demands for speed on Sercos are less than those for competitive interfaces that offer power stage control.