Protocols; Process Data Objects (Pdos); Service Data Object (Sdo) Parameter Access - Control Techniques Nidec SI-EtherCAT User Manual

6

Protocols

6.1

Process Data Objects (PDOs)

Cyclic data is implemented on EtherCAT networks by using "Process Data Objects" or PDOs.
Separate data objects are used for transmitting (TxPDOs) and receiving (RxPDOs) data. PDO
configuration objects are usually pre-configured in the EtherCAT master controller and downloaded
to the SI-EtherCAT at network Initialization using SDOs.
6.2

Service Data Object (SDO) parameter access

The service data object (SDO) provides access to all objects in the EtherCAT object dictionary and
the drive parameters are mapped into the object dictionary as 0x2XXX objects in the following way:
Index: 0x2000 + (0x100 x S) + menu number
Sub-index: 0x00 + parameter number
For example Pr 20.021 would be index 0x2014 and the sub-index would be 0x15. The values are
usually expressed in base 16 (hexadecimal), so care must be taken to enter the correct parameter
number.
All other supported entries in the SI-EtherCAT object dictionary can also be accessed using SDOs.
Refer to the master controller documentation for full details about implementing SDO transfers
within the particular master controller.
Bit parameter mapping
When mapping to drive bit parameters, the parameter is stored in the drive as an 8-bit value,
therefore for correct operation, the data type SINT (short integer) should be used for mapping to
these parameters.
The following table shows the drive bit parameter value for a given value in the EtherCAT master.
Table 6-1 Drive bit parameter value
EtherCAT Value
Decimal
-128 to 0
1 to 127
This is contrary to other option modules where any value other than zero will result in
NOTE
the parameter being set to a 1 (On).
Sub-index 0 for any menu will return the highest sub-index available for the object
NOTE
(i.e. the highest parameter number).
The following SDO services are supported:
NOTE
• Initiate SDO Download (Write)
• Initiate SDO Upload (Read)
• Abort SDO Transfer (Error)
SI-EtherCAT User Guide
Hex (0x)
80 to 00
01 to 7F
Parameter Value
0 (Off)
1 (On)
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