CAN Application Layer (CAL)
CAN in the OSI Reference Model
CiA DS 201 V 1.1
This document contains a description of the CAN Reference Model. This document is part of a set of documents that standardize the CAN Application Layer (CAL). The purpose of the CAN Reference Model and its related service- and protocol specifications is to make CAN an open network where modules from different suppliers can cooperate in distributed applications.
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CAN based Message Specification (CMS)
This document contains the service and protocol specification and the data types and encoding rules of the CAN based Message Specification (CMS). CMS is part of the CAN Application Layer. This document is part of a set of documents that standardize the CAN Application Layer for Industrial Applications.
These three parts are in the different documents:
CMS is one of the application layer service entities of the CAN Reference Model.
CMS is a language to specify what Communication Objects a module uses and how they are formatted. CMS can describe all CAN layer 2 features. This means also that existing applications can be described in CMS. Furthermore CMS offers the application a possibility to model its behaviour in the form of objects and remote services on these objects. This allows other applications to cooperate with it by executing these services that CMS supports on these objects.
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Network Management (NMT)
This document contains the service and protocol specification of the Network Management (NMT). NMT is part of the CAN Application Layer. This document is part of a set of documents that standardize the CAN Application Layer for Industrial Applications.
These two parts are in the different documents:
NMT is one of the application layer entities in the CAN Reference Model.
The NMT aids in the development of distributed applications. Due to the fact that an application is distributed, certain events have to be handles (e.g. failures of parts of the application) that would not occure if the same application had not been distributed.
The application has to deal with these network managment aspects, although they have nothing to do with goal of the application (e.g. controlling a process). These aspects are the consequence of building a distributed application and must be compared to the advantages of building a distributed application.
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Distributor (DBT)
This document contains the service and protocol specification of the Distributor (DBT). DBT is part of the CAN Application Layer. This document is part of a set of documents that standardize the CAN Application Layer for Industrial Applications.
These two parts are in the different documents:
The essential issue in creating an open system where modules from independent suppliers can cooperate via CAN, is how the identifiers and inhibit-times are assigned to the Communication Objects that a module uses. Identifiers are used by the Data Link Layer and inhibit-times are defined by the CMS service elemnt of the CAN Application Layer.
The DBT is a service element of the CAN Application Layer that offers dynamic distribution of identifiers and inhibit-times to the Communication Objects that a module uses. The dynamic distribution does not necessarily take place every time the module is 'powered on'. Depending on the facilities of the module, distribution may only be required once e.g. when the module is installed in the network.
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Layer Management (LMT)
This document contains the service and protocol specification of the Layer Management (LMT). LMT is part of the CAN Application Layer. This document is part of a set of documents that standardize the CAN Application Layer for Industrial Applications.
These two parts are in the different documents:
LMT is one of the application layer entities in the CAN Reference Model.
LMT offers the possibility to inquire and change the settings of certain parameters of the local layers on a CAN module with LMT Slave capabilities by a CAN module tih LMT Master capabilities via the CAN Network.
The following parameters can be inquired and/or changed by the use of LMT:
- NMT-address of the NMT Service Element
- bit timing parameters of the physical layer
- LMT address
By using LMT an LMT Slave can be configured for a CAN network without using any devices like DIP-switches for setting the parameters. There are several solutions available for LMT Slaves with and without a unique LMT-address or non-volatile storage.
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Recommended standard CAL module data sheet
CiA DS 206 V 1.1
This document contains a description of a recommended standard for a CAL module data sheet. The purpose of the recommended standard module data sheet is the provision of a standard description format for the complete specification of CAL-based modules in non-standardized-profile (proprietary) applications. The recommended Module Data Sheet consists of three parts and shall specify the functionality of a module as accessible from the bus. This means that not only the communication interface has to be specified but also the application specific functionality.
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Application layer naming conventions
CiA DS 207 V 1.1
This document contains the naming conventions that apply to instances of the objects that are defined by the service elements of the CAN Application Layer.
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