Tech Note #36: Introduction to the Alarm Clock Protocol (ACP)
1998 Bionic Buffalo Corporation; All Rights Reserved.
12 June 1998
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The server extends the lifetime of the specified request.
The server returns the status of the specified request.
The server provides a list of resources of the specified types. If clocks are listed, then
precision, accuracy, and base will be provided in the list.
Time of Day
The server returns the current time and date.
This section describes three reference applications using the Alarm Clock Protocol. These
applications defined the original design goals of the protocol.
The embedded system reference application consists of multiple, networked embedded
systems. Typically, these occur inside a complex machine such as an automobile,
aircraft, or in manufacturing machinery.
There may be from several to hundreds of processors in such an environment. These
processors usually require some degree of time or event synchronization. Although
many designs implement centralized control of synchronized operations, that approach
does not always easily permit add-on components which were not anticipated in the
original design. ACP provides a standardized design for components, which can be
used in diverse systems.
ACP allows individual nodes to be designed without precision clocks, since all nodes
can share a common, precision timebase. The event subscription services also provide a
way for an application simply to trigger preset operations on multiple nodes.
When writing an extremely portable application using multiple processes or tasks, the
design must be based on the “lowest common denominator” services expected to be
available on potential target platforms. This includes the following restrictions: