National Instruments Deterministic Ethernet Expansion Chassis NI 9144 - Manual (Page 13)

© National Instruments Corporation 13 NI 9144 User Guide and Specifications
Using the NI 9144 with an EtherCAT Third-Party Master
All of the functionality of the NI C Series modules is available to
third-party masters using vendor extensions to the object dictionary. The
NI 9144 is a modular device, meaning each module plugged into the
backplane has its own object dictionary, and each module configuration
is done through this dictionary. If your master software supports AoE
services (ADS over EtherCAT), you can address the module directly. If
your master software does not support AoE services, you can still configure
your module using NI vendor extensions and CoE (CAN over EtherCAT).
Using AoE/SDO
The AoE protocol allows you to specify the destination port or address of
the SDO request. An address of 0 indicates the NI 9144 device, while
addresses 1 through 8 route the SDO request to the object dictionary of the
module in the addressed slot. If no module is inserted in the addressed slot,
the request fails. SDOInfo and SDO requests work with module object
dictionaries over AoE in a manner similar to the NI 9144 main object
dictionary.
Depending on the master software interface, you may be required to add
1,000 to the slot number to create a valid AoE address.
For more information, refer to your C Series Module documentation.
Using CoE/SDO
The CoE protocol does not have a destination port or address, so the
NI 9144 provides an object dictionary entry that allows addressing support.
Prior to sending an SDO or SDOInfo request, your application can write a
slot number of 1 through 8 to the object dictionary index 0x5FFF subindex
0. Once this address is written, all future SDO transactions are sent to the
object dictionary of the module in the addressed slot. If no module is
inserted in the addressed slot, the request fails.
After the module-specific SDOInfo and SDO requests are complete, the
application writes 0 to the module’s object dictionary index 0x5FFF
subindex 0 to return control to the NI 9144 main object dictionary.
For a list of all chassis and module object dictionary entries, refer to
Appendix A .