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If you want to build a ship don't herd people together to collect wood and don't assign them tasks and work, but rather teach them to long for the endless immensity of the sea. (Antoine-Marie-Roger de Saint-Exupéry)

Mandatory communication entries


Device Type (1000h)

The Device Type is a 32-bit value that describes in a limited way some of the capabilities of the node. For example, it can describe if the node is a digital input/output module, and if so, whether inputs and/or outputs are implemented.

Error Register (1001h)

The Error Register is an 8-bit value that can indicate if various generic errors have occurred in the node, for example, current error, temperature error, communication error, etc. The only bit that must be implemented is the generic error bit. There is a manufacturer specific bit available to indicate an application specific error. This byte is also transmitted in Emergency Objects.

Guard Time (100Ch)

Nodes must support either heartbeats or node guarding. Both mechanisms are discussed later in this chapter. To summarize, these mechanisms allow nodes to determine if a specific node is alive and well and able to communicate to the network, along with the node’s current state. The Guard Time is a 16-bit value that specifies how frequently the node guarding request is transmitted by the master or must be received by the node. This entry must be implemented if heartbeats are not used.

Life Time Factor (100Dh)

The Life Time Factor is an 8-bit value that works with the Guard Time. It specifies how many multiples of the Guard Time must pass without transmission from the master or reception of a response from a slave before an error condition is generated. This entry must be implemented if heartbeats are not used.

Producer Heartbeat Time (1017h)

If the node is not using node guarding then it must implement heartbeats. This entry specifies how often the node should transmit heartbeat messages. It can be set to zero, however, to disable heartbeat transmission. This entry must be implemented if node guarding is not used.

Identity Object (1018h)

The Identity Object provides identifying information about the node. It must contain at a minimum the CAN In Automation assigned Vendor ID, which is unique to a particular vendor. It may also contain a product code to identify the product the node is in, a revision number and a serial number.