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The EtherCAT specification requires this Sync Manager usage:

Sync Manager Usage

Input Only slaves can use Sync Manager 2 as Input.

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This protocol allows to access a CANopen object dictionary. CANopen is a common field bus based on CAN. CoE allows to organize the acyclic data in an object dictionary. The object Dictionary is divided into different areas.

CoE Object Dictionary

Just like in CANopen there are services to upload and download these objects also known as SDOs (Service Data Objects). The slave can also send an Emergency message to the master to propagate local errors. In contrast to CANopen a CoE message is not limited to 8 bytes, thus allowing a more efficient data transfer. Additionally the SDO Info Service is provided that enables the master to completely read all meta information about all objects. CoE also introduces Complete Access. This method can be used to upload or download all sub-indices of an object at once. If an object does not fit into a mailbox, it can be exchanged via Segmented SDO transfer.

There are special objects reserved to define the PDO mapping. A PDO (Process Data Object) determines which objects are cyclically transfered as process data. There are special PDO mapping objects. Each object can have several entries. Each entry defines the index, sub-index and bit size of an object that is used for process data.

PDO mapping objects

Each Sync Manager has a PDO Assignment Object (0x1C10 - 0x1C2F). Its entries list the PDO Mapping objects that are assigned to a Sync Manager.

Sync Manager Assignment objects

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Figure 4: PDO Mapping in EtherCAT

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Slave behavior in all EtherCAT states

Not all state transition are possible. The following figure shows all allowed transitions.

Image RemovedImage Added

Figure 5: EtherCAT State Machine

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Introduction to CC-Link IE TSN

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CC Link IE TSN is an ethernet based industrial communication stack. It is based on earlier CC Link IE concepts, uniting them with the ideas of time synchronized networking (TSN). The standards are maintained by the CC Link Partners Association (CLPA). 

In a CC-Link IE TSN network, all stations perform time synchronization using either PTP IEEE1588v2 or gPTP IEEE802.1AS. The time synchronization is performed in the initialization sequence and periodically during the runtime sequence.

Communications are performed with the communication cycle divided into time slots as a time sharing method. Settings related to the time sharing method are configured once in the initialization sequence.

Communication Cycle	Time slot	Cycle start offset	Cycle end offset	Available Ethernet frame for communications
				EtherType	Category
10 ms	TSLT1	0 ms	5 ms	0x890F	CC-Link IE TSN network
	TSLT2	5 ms	6 ms	0x88F7	Time synchronization
	TSLT0	6 ms	10 ms	All others	IP communication (such as SLMP, CC-Link IE Field Network Basic), etc.

Table 3: Example of time slots in a cycle

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The data that is transferred, is locally organized in so-called link devices. These differentiate by direction and by data type.

 

Name	Size of an element	Direction	Content
RX	1 Bit	To Master	Input	Digital, “Points”
RY	1 Bit	To Remote Station	Output	Digital, “Points”
RWr	2 Byte	To Master	Input	Compound Data, “Words”
RWw	2 Byte	To Remote Station	Output	Compound Data, “Words”
Safety In			Input	*
Safety Out			Output	*
Statusword	8 Byte	To Master		Status Information (standardized content)

Table 4: Overview of link devices

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