Positioning module IMD20, IMD40
CanOpen protocol
Ca
Overv
he communication in CanOpen networks is based upon CAN data packages the content (max. 8
bytes) and target address of which are used by the CanOpen protocol.
The main part of the communication is handled via the communications objects SDO (Service Data
Object) and PDO (Process Data Object).
Each CanOpen participant has a reserve of variables and parameters that are arranged in an object
ctory with defined addresses and that can be read or written via the network.
nOpen protocol
iew
T
dire
A CanOpen participant can be subdivided into three functional blocks:
Communication Object
directory
Application
Sending and receiving of
communication objects.
et
Administration of communications
parameters.
c
d
meters.
Application programme, e.g.
control of a drive, I/O
administration.
Implementation of the device
profile.
SDO, PDO, SYNC, c.
Interfa e to inte
para
rnal variables an
Apart from the two objects
r the
ran fer, t
s objects, e.g. for
the synchronisation or error messages. All in all,
d:
ni
tions bjec
S ort de
ripti
fo
data t
s
here are still further communication
the following CanOpen objects are supporte
Commu ca
o
t
h
sc
on
SDO
Universal
mmu
objects contained
er than PDO since the
o
ct add
s ha
a second SDO ha
co
nications channel for the reading and writing of all
in an objects directory. Slow
bje
res
s always also to be transferred and since a feedback via
s to be realised.
PDO
Communications
the exchange of process data. Fast transfer,
since the d ta are
channel for
a
sent without protocol overhead.
EMCY
Emergency object for the transfer of error messages.
SYNC
The synchronisati
ct allows a synchronous operation of several bus
participants.
on obje
NODE GUARDING
Monitoring of the bus participants through the exchange of cyclical
messages.
NMT OBJECT
Control of the basic states of all bus participants.
The following figure tries to display the communication with a CanOpen device via SDO or PDO.
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