Sending And Receiving Data In Ethercat (Coe) Communications; Coe Terminology - YASKAWA SGD7S-1R9D Product Manual

1.2 Introduction to EtherCAT

1.2.3 Sending and Receiving Data in EtherCAT (CoE) Communications

1.2.3 Sending and Receiving Data in EtherCAT (CoE) Commu-
nications
Objects are used to send and receive data in EtherCAT (CoE) communications.
Reading and writing object data is performed in process data communications (PDO service),
which transfers data cyclically, and in mailbox communications (SDO service), which transfers
data non-cyclically.
Process data communications are used to read and write PDOs. Mailbox communications
(SDO) are used to read and write object dictionary data entries.
1.2.4

CoE Terminology

The EtherCAT and CANopen terms that are used in this manual are described in the following
table.
CAN in Automation
Controller Area Network
CANopen
CANopen over EtherCAT
Distributed Clocks
Electrically Erasable
Programmable Read Only
Memory
EtherCAT Slave Controller
EtherCAT State Machine
EtherCAT Technology Group
Ethernet for Control
Automation Technology
Fieldbus Memory
Management Unit
INIT
OPERATIONAL
Object Dictionary
Process Data Object
Process Data Object
Mapping
Service Data Object
PRE-OPERATIONAL
Process data
1-4
Term Abbreviation
CiA
CAN
CANopen
CoE
DC
EEPROM
ESC
ESM
ETG
EtherCAT
FMMU
INIT
OP
OD
PDO
PDO mapping
SDO
PREOP
–
Description
A non-profit organization established in 1992 as a joint ven-
ture between companies to provide CAN technical informa-
tion, product information, and marketing information.
Communications protocol for the physical layer and data link
layer established for automotive LANs. It was established as
an international standard as ISO 11898.
An upper-layer protocol based on the international CAN stan-
dard (EN 50325-4).
It consists of profile specifications for the application layer,
communications, applications, devices, and interfaces.
A network that uses Ethernet for the physical layer, EtherCAT
for the data link layer, and CANopen for the application layer
in a seven-layer OSI reference model.
A clock distribution mechanism that is used to synchronize
the EtherCAT slaves with the EtherCAT master.
A ROM that can be electrically overwritten.
A hardware chip that processes EtherCAT communications
(such as loopbacks) and manages the distributed clock.
A state machine in which the state of EtherCAT (the data link
layer) changes according to transition conditions.
An international organization established in 2003 to provide
support for developing EtherCAT technologies and to pro-
mote the spread of EtherCAT technologies.
An open network developed by Beckhoff Automation.
A unit that manages fieldbus memory.
The Init state in the EtherCAT state machine.
The Operational state in the EtherCAT state machine.
A group of objects and structure supported by an EtherCAT
SERVOPACK.
Objects that are sent and received in cyclic communications.
Definitions of the applications objects that are sent with
PDOs.
Objects that are sent and received in mailbox communica-
tions.
The Pre-operational state in the EtherCAT state machine.
The data contained in application objects that are periodically
transferred for measurements or controls.
Continued on next page.