User Manual

CANopen Manual for TMCM-1140, TMCM-1160, and TMCM-1180 (Rev. 2.01 / 2017-JUL-26) 9
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2 Communication
2.1 Reference Model
The application layer comprises a concept to configure and communicate real-time-data as well as the
mechanisms for synchronization between devices. The functionality the application layer offers to an
application is logically divided over different service data objects (SDO) in the application layer. A service
object offers a specific functionality and all the related services.
Applications interact by invoking services of a service object in the application layer. To realize these
services this object exchanges data via the CAN Network with peer service object(s) using a protocol.
The application and the application layer interact with service primitives.
SERVICE PRIMITIVES
Request
Issued by the application to the application layer to request a service.
Indication
Issued by the application layer to the application to report an internal event detected
by the application layer or indicate that a service is requested.
Response
Issued by the application to the application layer to respond to a previous received
indication.
Confirmation
Issued by the application layer to the application to report the result of a previously
issued request.
Table 2.1 Service primitives
A service type defines the primitives that are exchanged between the application layer and the cooperating
applications for a particular service of a service object. Unconfirmed and confirmed services are collectively
called remote services.
SERVICE TYPES
Local service
Involves only the local service object. The application issues a request to its local
service object that executes the requested service without communicating with peer
service object(s).
Unconfirmed
service
Involves one or more peer service objects. The application issues a request to its
local service object. This request is transferred to the peer service object(s) that each
passes it to their application as an indication. The result is not confirmed back.
Confirmed
service
Can involve only one peer service object. The application issues a request to its local
service object. This request is transferred to the peer service object that passes it to
the other application as an indication. The other application issues a response that is
transferred to the originating service object that passes it as a confirmation to the
requesting application.
Provider
initiated service
Involves only the local service object. The service object (being the service provider)
detects an event not solicited by a requested service. This event is then indicated to
the application.
Table 2.2 Service types