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Diffstat (limited to '')
| -rw-r--r-- | doc/user/concepts.t | 42 |
1 files changed, 36 insertions, 6 deletions
diff --git a/doc/user/concepts.t b/doc/user/concepts.t index e81738be00..5afc317128 100644 --- a/doc/user/concepts.t +++ b/doc/user/concepts.t @@ -43,15 +43,32 @@ reflect the object's use in the application. Conversely, object IDs are designed to facilitate efficient object manipulation by the executive. +@subsection Object Names + @cindex object name +@findex rtems_object_name An object name is an unsigned thirty-two bit entity -associated with the object by the user. Although not required -by RTEMS, object names are typically composed of four ASCII -characters which help identify that object. For example, a task -which causes a light to blink might be called "LITE". Utilities -are provided to build an object name from four ASCII characters -and to decompose an object name into four ASCII characters. +associated with the object by the user. The data type +@code{@value{DIRPREFIX}name} is used to store object names. + +@findex rtems_build_name + +Although not required by RTEMS, object names are often +composed of four ASCII characters which help identify that object. +For example, a task which causes a light to blink might be +called "LITE". The @code{@value{DIRPREFIX}build_name} routine +is provided to build an object name from four ASCII characters. +@ifset is-C +The following example illustrates this: + +@example +rtems_object_name my_name; + +my_name = rtems_build_name( 'L', 'I', 'T', 'E' ); +@end example +@end ifset + However, it is not required that the application use ASCII characters to build object names. For example, if an application requires one-hundred tasks, it would be difficult to @@ -59,13 +76,18 @@ assign meaningful ASCII names to each task. A more convenient approach would be to name them the binary values one through one-hundred, respectively. +@subsection Object IDs + @cindex object ID @cindex object ID composition +@findex rtems_id @need 3000 An object ID is a unique unsigned thirty-two bit entity composed of three parts: object class, node, and index. +The data type @code{@value{DIRPREFIX}id} is used to store object IDs. + @ifset use-ascii @example @@ -259,6 +281,8 @@ known as a tick. The frequency of clock ticks is completely application dependent and determines the granularity and accuracy of all interval and calendar time operations. +@findex rtems_interval + By tracking time in units of ticks, RTEMS is capable of supporting interval timing functions such as task delays, timeouts, timeslicing, the delayed execution of timer service @@ -267,6 +291,8 @@ interval is defined as a number of ticks relative to the current time. For example, when a task delays for an interval of ten ticks, it is implied that the task will not execute until ten clock ticks have occurred. +All intervals are specified using data type +@code{@value{DIRPREFIX}interval}. A characteristic of interval timing is that the actual interval period may be a fraction of a tick less than the @@ -291,6 +317,10 @@ date and time. This allows selected time operations to be scheduled at an actual calendar date and time. For example, a task could request to delay until midnight on New Year's Eve before lowering the ball at Times Square. +The data type @code{@value{DIRPREFIX}time_of_day} is used to specify +calendar time in RTEMS services. +@xref{Clock Manager Time and Date Data Structures, , Time and Date Data Structures}. +@findex rtems_time_of_day Obviously, the directives which use intervals or wall time cannot operate without some external mechanism which |