Festo EMCA-EC-67 CO Series, Description

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D CANopen communication
Festo – EMCA-EC-C-HP-EN – 2017-11e – English 325
D.4 PDO message (PDO message)
With PDO (Process data object), data can be transmitted in an event-driven manner or cyclically. The
PDO thereby always transmits one or more previously established parameters. Other than with service
data objects SDO (Service data objects), there is no acknowledgment when PDOs are transmitted. After
PDO activation with Start node, all recipients must therefore be able to process any arriving PDOs at
any time. The advantage is that all operation-relevant data are transmitted bundled in one message,
which results in a strong reduction of the CAN-bus workload.
A distinction is made between the following types of PDOs:
Type communication Description
RPDO1 … 4 Controller
è
EMCA
(Receive)
When a certain event occurs, the master sends a PDO to
the EMCA.
TPDO1 … 4 EMCA
è
Controller
(Transmit)
When a certain event occurs in asynchronous mode
(value change), the EMCA sends a TPDO to the master.
In synchronous mode, the TPDO are sent within the cycle
time after receipt of the SYNC message.
Tab. D.4 PDO types