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5.3.3.3 Node Guarding Protocol

By means of Node Guarding, the NMT slave is cyclically requested via an RTR frame to send its current status. Additional toggling of a bit detects whether or not the NMT slave still operates correctly.

5.3.3.4 Heartbeat Protocol

This protocol allows monitoring without RTR frames. A heartbeat generator cyclically generates a heartbeat message received by n subscribers. The heartbeat message contains the coding of the current generator status.

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5.3.3.5 Bootup Protocol

This protocol shows that the NMT slave has changed its status from INITIALIZING to PRE-OPERATIONAL. This is performed after a hardware/software reset or following the service reset code.

5.3.4 Object Directory

The object directory is the central point of a CANopen subscriber where all configuration information and data is stored and can be polled. The directory organization is by means of tables and contains three areas of CANopen objects:

•Communication Profile Area (Index 0x1000 – 0x1FFF)

This profile contains all parameters relevant for CANopen communication. This area is identical for all CANopen subscribers.

•Manufacturer Specific Profile Area (Index 0x2000 – 0x5FFF)

In this profile, each manufacturer can implement his own company specific objects.

•Standardized Device Profile Area (Index 0x6000 – 0x9FFF)

This profile contains all objects which are assisted by a certain device profile. The bus coupler assists the device profile DS-401 (Device Profile for Generic I/O Modules)

In the object directory, a logical addressing scheme is used for the access to communication and device parameters, data and functions. Each entry into the directory is identified by a 16 bit index which indicates the row address of the table. A maximum of 65536 entries are permitted.

If an object is composed of several components, the components are identified by means of an 8 bit sub-index. The sub-index indicates the individual column address of the table allowing a maximum of 256 entries.

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Each entry consists of:

•an object name describing the object function,

•a data type attribute defining the data type of the entry, and

•an access attribute indicating whether the entry is only read, only write or read and write.

The sub-index 0 indicates the max. number of the following sub-indexes. The data is coded in the following sub-indexes.

Table 5-2: Structure of the CANopen object directory

The object directory structure is designed for the worst case. Object entries that cannot be used because of the connected module configuration are deactivated.

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5.3.4.1 Initialization

The connected module configuration is determined following power On.

If a customer-specific configuration was saved and if the currently connected module configuration coincides with the one last saved, the object directory with this saved configuration will be initialized.

In every other case, object directory will be assigned a default configuration.

5.3.4.1.1 Default configuration 5.3.4.1.1.1Initialization Communication Profile Area

All objects of this profile assisted by the bus coupler are initialized according to the default values of DS 301 (CANopen Application Layer and Communication Profile).

• Entry of the default mapping parameters:

Pre-assignment of the mapping parameters depends on the device profile used. The bus coupler assists the DS 401 profile, and as such the process described there is used. The first 4 Rx-/TxPDOs are defined as default PDOs. If more inputs/outputs exist at the bus coupler than can be covered with the default PDOs, from Rx-/TxPDO 5 all remaining I/Os are entered. First all digital, then all analog I/Os are entered. If more than 64 digital I/Os per input/output are available, a continuation is only made with PDO 5, even if no analog modules exist. PDO 2 to 4 will then remain unused. Furthermore, only one data type is used as a default entry for a PDO, in other words, if a 3 byte and a 4 byte module exists, then a default is entered for each of the 2 PDOs.

1. RxPDO:

contains maximum the first 8x8 digital outputs. If no digital outputs exist, the sub index 0 has the default value 0, and this PDO is not used with its default value.

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2. RxPDO:

contains max. the 1st to 4th 16 bit analog output. If no 16 bit analog outputs exist, the sub index 0 has the default value 0, and this PDO is not used with its default value.

3. RxPDO:

contains maximum the 5th to 8th bit analog output. If more than 4 16 bit analog outputs exist, the sub index 0 has the default value 0, and this PDO is not used with its default value.

4. RxPDO:

contains maximum the 9th to 12th 16 bit analog output. If not more than 8 16 bit analog outputs exist, the sub index 0 has the default value 0, and this PDO is not used with its default value.

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