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This makes it easier to automatically generate parts of the manager documentation in the future. Update #3993.
85 lines
3.6 KiB
ReStructuredText
85 lines
3.6 KiB
ReStructuredText
.. SPDX-License-Identifier: CC-BY-SA-4.0
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.. Copyright (C) 1988, 2008 On-Line Applications Research Corporation (OAR)
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Operations
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==========
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Creating a Timer
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----------------
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The ``rtems_timer_create`` directive creates a timer by allocating a Timer
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Control Block (TMCB), assigning the timer a user-specified name, and assigning
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it a timer ID. Newly created timers do not have a timer service routine
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associated with them and are not active.
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Obtaining Timer IDs
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-------------------
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When a timer is created, RTEMS generates a unique timer ID and assigns it to
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the created timer until it is deleted. The timer ID may be obtained by either
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of two methods. First, as the result of an invocation of the
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``rtems_timer_create`` directive, the timer ID is stored in a user provided
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location. Second, the timer ID may be obtained later using the
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``rtems_timer_ident`` directive. The timer ID is used by other directives to
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manipulate this timer.
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Initiating an Interval Timer
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----------------------------
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The ``rtems_timer_fire_after`` and ``rtems_timer_server_fire_after`` directives
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initiate a timer to fire a user provided timer service routine after the
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specified number of clock ticks have elapsed. When the interval has elapsed,
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the timer service routine will be invoked from a clock tick
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directive if it was initiated by the ``rtems_timer_fire_after`` directive and
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from the Timer Server task if initiated by the
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``rtems_timer_server_fire_after`` directive.
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Initiating a Time of Day Timer
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------------------------------
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The ``rtems_timer_fire_when`` and ``rtems_timer_server_fire_when`` directive
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initiate a timer to fire a user provided timer service routine when the
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specified time of day has been reached. When the interval has elapsed, the
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timer service routine will be invoked from a clock tick directive
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by the ``rtems_timer_fire_when`` directive and from the Timer Server task if
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initiated by the ``rtems_timer_server_fire_when`` directive.
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Canceling a Timer
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-----------------
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The ``rtems_timer_cancel`` directive is used to halt the specified timer. Once
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canceled, the timer service routine will not fire unless the timer is
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reinitiated. The timer can be reinitiated using the ``rtems_timer_reset``,
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``rtems_timer_fire_after``, and ``rtems_timer_fire_when`` directives.
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Resetting a Timer
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-----------------
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The ``rtems_timer_reset`` directive is used to restore an interval timer
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initiated by a previous invocation of ``rtems_timer_fire_after`` or
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``rtems_timer_server_fire_after`` to its original interval length. If the
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timer has not been used or the last usage of this timer was by the
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``rtems_timer_fire_when`` or ``rtems_timer_server_fire_when`` directive, then
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an error is returned. The timer service routine is not changed or fired by
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this directive.
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Initiating the Timer Server
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---------------------------
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The ``rtems_timer_initiate_server`` directive is used to allocate and start the
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execution of the Timer Server task. The application can specify both the stack
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size and attributes of the Timer Server. The Timer Server executes at a
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priority higher than any application task and thus the user can expect to be
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preempted as the result of executing the ``rtems_timer_initiate_server``
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directive.
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Deleting a Timer
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----------------
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The ``rtems_timer_delete`` directive is used to delete a timer. If the timer
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is running and has not expired, the timer is automatically canceled. The
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timer's control block is returned to the TMCB free list when it is deleted. A
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timer can be deleted by a task other than the task which created the timer.
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Any subsequent references to the timer's name and ID are invalid.
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