Process Data Objects - Lenze i55AE125B Manual

Configuring the network
CANopen

Process data objects

9.4.8 Process data objects
Process data objects (PDOs) are used for the cyclic transmission of (process) data via CAN-
open. PDOs only contain data and an identifier. They do not contain any information about
the sender or receiver and are therefore very efficient.
Details
Process data objects which the inverter receives via the network are referred to as
•
"Receive PDOs" (RPDOs).
Process data objects which the inverter sends via the network are referred to as "Transmit
•
PDOs" (TPDOs).
The maximum length of a PDO is 8 bytes (4 data words).
•
Each PDO requires a unique identifier ("COB-ID") for the purpose of identification within
•
the network.
Communication parameters such as the transmission type and cycle time for each PDO
•
can be set freely and independently of the settings of other PDOs
Transmission type
Process data objects can be transmitted in an event-controlled or time-controlled manner. The
below table shows that it is possible to combine the different methods by means of logic
operations (AND, OR):
Event-controlled: The PDO is sent if a special device-internal event has occurred, for
•
instance, if the data contents of the TPDO have changed or if a transmission cycle time has
elapsed.
Synchronous transmission: Transmission of a TPDOs or reception of an RPDO is effected
•
after the inverter has received a sync telegram (COB-ID 0x80).
Cyclic transmission: The cyclic transmission of PDOs is effected when the transmission
•
cycle time has elapsed.
Polled via RTR: Transmission of a TPDO is carried out on request by another device via data
•
request frame (RTR remote transmit request). For this, the data requester (e.g. master)
sends the data request frame with the COB-ID of the TPDO that is to be requested to
transmit. The receiver recognises the RTR and carries out the transmission.
Transmission type
0
1 ... 240
254, 255
Transmission type Description
0 Synchronous and acyclic
• The PDO is transmitted on an event-controlled basis with every sync (e.g. when a bit change occurs in the PDO).
1 ... 240 Synchronous and cyclic (sync-controlled with a response)
• Selection n = 1: The PDO is transmitted with every sync.
• Selection 1 < n ≤ 240: The PDO is transmitted with every n-th sync.
241 ... 251 Reserved
252 Synchronous - RTR only
253 Asynchronous - RTR only
254, 255 Asynchronous - manufacturer-specific / device profile-specific
• If one of these values is entered, the PDO is transferred in an event-controlled or cyclic manner. (The values "254"
and "255" are equivalent).
• For a cyclic transmission, a cycle time must be entered for the respective PDO. In this case, cyclic transmission
takes place in addition to event-controlled transmission.
266
PDO transmission
cyclic synchronous
l
l
l
Logic combination of differ-
ent transmission types
event-controlled
AND
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-
OR
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