Chapter 2 Decentral block periphery CAN-Bus CANopen
Manual VIPA System 100V
2-24
HB100E - SM-CAN - Rev. 15/02
SDO - Service Data Object
For accesses on the object directory the
s
ervice
d
ata
o
bject (SDO) is used.
With the help of the SDO you may access the object directory for reading or
writing. In the CAL-Layer-7-Protocol you find the specification of the
Multiplexed-Domain-Transfer-Protocol, that is used by the SDOs. With this
protocol you may transfer messages of undefined length. Hereby
messages may be divided in several CAN messages with identical identifier
(segmentation) if necessary.
In the first CAN message of the SDO 4 of the 8 bytes are occupied by
protocol information. For access on object directory entries with a length up
to 4 bytes, a single CAN message is sufficient. For data lengths more than
4 bytes a segmented transmission takes place. The following segments of
the SDO contain up to 7 bytes user data. The last byte contains an end
identifier. A SDO is transmitted confirmed, i.e. every receipt of a message
is acknowledged.
The COB identifier for read and write access are:
•
Receive-SDO1: 0x600 + Module-ID
•
Transmit-SDO1: 0x580 + Module-ID
•
Receive-SDO2: 0x640 + Module-ID
•
Transmit-SDO2: 0x5C0 + Module-ID
Note!
A more detailed description of the SDO telegrams is to find in the DS-301
norm from CiA.
In the following we will describe only those error messages that are thrown
at a wrong parameter communication.