CAN Communication
CANopen Application Layer
EPOS4 Communication Guide
CCMC | 2019-11 | rel8759
3-25
3.3 CANopen Application Layer
3.3.1 Object Dictionary
The most significant part of a CANopen device is the Object Dictionary. It is essentially a grouping of objects
accessible via the network in an ordered, predefined fashion. Each object within the dictionary is addressed
using a 16-bit index and a 8-bit subindex. The overall layout of the standard Object Dictionary conforms to
other industrial field bus concepts.
Table 3-8 CAN communication – Object dictionary layout
A 16-bit index is used to address all entries within the Object Dictionary. In case of a simple variable, it ref-
erences the value of this variable directly. In case of records and arrays however, the index addresses the
entire data structure. The subindex permits individual elements of a data structure to be accessed via the
network.
• For single Object Dictionary entries (such as UNSIGNED8, BOOLEAN, INTEGER32, etc.), the
subindex value is always zero.
• For complex Object Dictionary entries (such as arrays or records with multiple data fields), the sub-
index references fields within a data structure pointed to by the main index.
An example: A receive PDO, the data structure at index 1400h defines the communication parameters for
that module. This structure contains fields or the COB-ID and the transmission type. The subindex concept
can be used to access these individual fields as shown below.
Table 3-9 CAN communication – Object dictionary entry
Index Variable accessed
0x0000 Reserved
0x0001…0x025F Data types (not supported on EPOS4)
0x0260…0x0FFF Reserved
0x1000…0x1FFF Communication Profile Area (CiA 301)
0x2000…0x5FFF Manufacturer-specific Profile Area (maxon)
0x6000…0x9FFF Standardized profile area 1st…8th logical device
0xA000…0xAFFF Standardized network variable area (not supported on EPOS4)
0xB000…0xBFFF Standardized system variable area (not supported on EPOS4)
0xC000…0xFFFF Reserved (not supported on EPOS4)
Index Subindex Variable accessed Data Type
1400h 0 Number of entries UNSIGNED8
1400h 1 COB-ID used by RxPDO 1 UNSIGNED32
1400h 2 Transmission type RxPDO 1 UNSIGNED8
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