DESIGN OF A CUSTOM ASIC INCORPORATING CAN™ AND 1 ...

nodes that do not have an associated address when they have already been connected to the
network [41].
The Automatic Node Discovery (AND) protocol [41] introduces a technique that enables
nodes in a CANopen® network to be dynamically identified, so that their addresses can be
assigned correctly. The overall configuration mechanism consists of two separate phases: node
identification and address assignment. In the node identification phase the Layer Setting
Services (LSS) master, one of two protocols included with CANopen®, discovers the different
nodes in the network. Once this task is finished, the address assignment phase is started. Since
the address assignment scheme for the slaves affects the precedence of the messages they
transmit, the timing requirements of the different data exchanges have to be somehow known in
this phase. This aspect is covered in more detail in [49] and [50].
The AND algorithm enables slave devices to be discovered quickly when they are
already connected to the final system. This is achieved by adding some communication services
to the basic LSS protocol, so that the nonconfigured nodes can be identified. In [41] two
versions of the discovery algorithm are described, that are nonrecursive and recursive,
respectively. The former facilitates implementations, while the latter runs faster. The AND
protocol is efficient and requires few changes to the firmware of the slave devices and provides a
good degree of compatibility with the devices currently available off the shelf [41].
4.3.3 Event-Triggered vs. Time-Triggered Control Paradigms
One of the elementary requirements of all real-time systems is the ability to react to an
asynchronous event within a predefined period of time. At present, two different control
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