BECKHOFF AX2000 CANopen communication profile - Manual (Page 21)

3.4.5 Service Data Objects (SDO)
SDOs are used to implement access to the Object Dictionary. The SDOs are required for parame-
trerization and for status polling. Access to an individual Object is made with a multiplexer via the
Index and Sub-index of the Object Dictionary. The following communication protocols are supported
by AX2000/2500:
l Initiate SDO Download Protocol
l Download SDO Segment Protocol
l Initiate SDO Upload Protocol
l Upload SDO Segment Protocol
l Abort SDO Transfer Protocol
The definitions of the individual communication services and protocols can be found in DS301.
Examples of the usage of SDOs can be found in the application section of this manual.
Note!
Since an SDO is a confirmed service, the system must always wait for the SDO response
telegram before it is allowed to transmit a new telegram.
3.4.5.1 Composition of the Service Data Object
An SDO is consists of the following components:
Byte 1 2 3 4 5 6 7 8
Content rw Index Sub-index Data
1. The control byte (Byte 1):
The control byte determines whether the SDO has write or read access to the entry in the
Object Dictionary. A description of the complete Object Dictionary for
AX2000/2500 can be found in Section 6.3.
Data exchange with the AX2000/2500 is governed by the CMS
multiplexed domain protocols standard, as described in the CAN standard DS 202.
To read data, the control byte must be written in the manner shown below:
Bit 7 6 5 4 3 2 1 0
Content ccs*=2 0 0 0 0 0
* ccs Þ client command specifier (ccs = 2 Þ initiate download request)
So a value of 0100 0000 (binary) or 40h has to be transmitted in the control byte.
The servo amplifier sends back a corresponding response byte:
Bit 7 6 5 4 3 2 1 0
Content scs*=2 X n e s
* scs Þ server command specifier (scs = 2 Þ initiate upload response)
n Þ only valid for e = s = 1
if this is so, n contains the number of bytes that do not contain data
X Þ free data
If reading is successfull, the response byte always has set the bits 0 and 1 (e = s = 1).
Encoded byte length in the SDO response:
0x43 - 4 bytes
0x47 - 3 bytes
0x4B - 2 bytes
0x4F - 1 byte.
CANopen for AX2000/2500 21
BECKHOFF
07/2007
CANopen communication profile