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authorJoel Sherrill <joel.sherrill@OARcorp.com>1997-05-27 12:40:11 +0000
committerJoel Sherrill <joel.sherrill@OARcorp.com>1997-05-27 12:40:11 +0000
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+@c
+@c COPYRIGHT (c) 1996.
+@c On-Line Applications Research Corporation (OAR).
+@c All rights reserved.
+@c
+
+@ifinfo
+@node Glossary, Command and Variable Index, Example Application, Top
+@end ifinfo
+@chapter Glossary
+
+@table @b
+@item active
+A term used to describe an object
+which has been created by an application.
+
+@item aperiodic task
+A task which must execute only at
+irregular intervals and has only a soft deadline.
+
+@item application
+In this document, software which makes
+use of RTEMS.
+
+@item ASR
+see Asynchronous Signal Routine.
+
+@item asynchronous
+Not related in order or timing to
+other occurrences in the system.
+
+@item Asynchronous Signal Routine
+Similar to a hardware
+interrupt except that it is associated with a task and is run in
+the context of a task. The directives provided by the signal
+manager are used to service signals.
+
+@item awakened
+A term used to describe a task that has
+been unblocked and may be scheduled to the CPU.
+
+@item big endian
+A data representation scheme in which
+the bytes composing a numeric value are arranged such that the
+most significant byte is at the lowest address.
+
+@item bit-mapped
+A data encoding scheme in which each bit
+in a variable is used to represent something different. This
+makes for compact data representation.
+
+@item block
+A physically contiguous area of memory.
+
+@item blocked
+The task state entered by a task which has
+been previously started and cannot continue execution until the
+reason for waiting has been satisfied.
+
+@item broadcast
+To simultaneously send a message to a
+logical set of destinations.
+
+@item BSP
+see Board Support Package.
+
+@item Board Support Package
+A collection of device
+initialization and control routines specific to a particular
+type of board or collection of boards.
+
+@item buffer
+A fixed length block of memory allocated
+from a partition.
+
+@item calling convention
+The processor and compiler
+dependent rules which define the mechanism used to invoke
+subroutines in a high-level language. These rules define the
+passing of arguments, the call and return mechanism, and the
+register set which must be preserved.
+
+@item Central Processing Unit
+This term is equivalent to
+the terms processor and microprocessor.
+
+@item chain
+A data structure which allows for efficient
+dynamic addition and removal of elements. It differs from an
+array in that it is not limited to a predefined size.
+
+@item coalesce
+The process of merging adjacent holes into
+a single larger hole. Sometimes this process is referred to as
+garbage collection.
+
+@item Configuration Table
+A table which contains
+information used to tailor RTEMS for a particular application.
+
+@item context
+All of the processor registers and
+operating system data structures associated with a task.
+
+@item context switch
+Alternate term for task switch.
+Taking control of the processor from one task and transferring
+it to another task.
+
+@item control block
+A data structure used by the
+executive to define and control an object.
+
+@item core
+When used in this manual, this term refers to
+the internal executive utility functions. In the interest of
+application portability, the core of the executive should not be
+used directly by applications.
+
+@item CPU
+An acronym for Central Processing Unit.
+
+@item critical section
+A section of code which must be
+executed indivisibly.
+
+@item CRT
+An acronym for Cathode Ray Tube. Normally used
+in reference to the man-machine interface.
+
+@item deadline
+A fixed time limit by which a task must
+have completed a set of actions. Beyond this point, the results
+are of reduced value and may even be considered useless or
+harmful.
+
+@item device
+A peripheral used by the application that
+requires special operation software. See also device driver.
+
+@item device driver
+Control software for special
+peripheral devices used by the application.
+
+@item directives
+RTEMS' provided routines that provide
+support mechanisms for real-time applications.
+
+@item dispatch
+The act of loading a task's context onto
+the CPU and transferring control of the CPU to that task.
+
+@item dormant
+The state entered by a task after it is
+created and before it has been started.
+
+@item Device Driver Table
+A table which contains the
+entry points for each of the configured device drivers.
+
+@item dual-ported
+A term used to describe memory which
+can be accessed at two different addresses.
+
+@item embedded
+An application that is delivered as a
+hidden part of a larger system. For example, the software in a
+fuel-injection control system is an embedded application found
+in many late-model automobiles.
+
+@item envelope
+A buffer provided by the MPCI layer to
+RTEMS which is used to pass messages between nodes in a
+multiprocessor system. It typically contains routing
+information needed by the MPCI. The contents of an envelope are
+referred to as a packet.
+
+@item entry point
+The address at which a function or task
+begins to execute. In C, the entry point of a function is the
+function's name.
+
+@item events
+A method for task communication and
+synchronization. The directives provided by the event manager
+are used to service events.
+
+@item exception
+A synonym for interrupt.
+
+@item executing
+The task state entered by a task after it
+has been given control of the CPU.
+
+@item executive
+In this document, this term is used to
+referred to RTEMS. Commonly, an executive is a small real-time
+operating system used in embedded systems.
+
+@item exported
+An object known by all nodes in a
+multiprocessor system. An object created with the GLOBAL
+attribute will be exported.
+
+@item external address
+The address used to access
+dual-ported memory by all the nodes in a system which do not own
+the memory.
+
+@item FIFO
+An acronym for First In First Out.
+
+@item First In First Out
+A discipline for manipulating
+entries in a data structure.
+
+@item floating point coprocessor
+A component used in
+computer systems to enhance performance in mathematically
+intensive situations. It is typically viewed as a logical
+extension of the primary processor.
+
+@item freed
+A resource that has been released by the
+application to RTEMS.
+
+@item global
+An object that has been created with the
+GLOBAL attribute and exported to all nodes in a multiprocessor
+system.
+
+@item handler
+The equivalent of a manager, except that it
+is internal to RTEMS and forms part of the core. A handler is a
+collection of routines which provide a related set of functions.
+For example, there is a handler used by RTEMS to manage all
+objects.
+
+@item hard real-time system
+A real-time system in which a
+missed deadline causes the worked performed to have no value or
+to result in a catastrophic effect on the integrity of the
+system.
+
+@item heap
+A data structure used to dynamically allocate
+and deallocate variable sized blocks of memory.
+
+@item heterogeneous
+A multiprocessor computer system
+composed of dissimilar processors.
+
+@item homogeneous
+A multiprocessor computer system
+composed of a single type of processor.
+
+@item ID
+An RTEMS assigned identification tag used to
+access an active object.
+
+@item IDLE task
+A special low priority task which assumes
+control of the CPU when no other task is able to execute.
+
+@item interface
+A specification of the methodology used
+to connect multiple independent subsystems.
+
+@item internal address
+The address used to access
+dual-ported memory by the node which owns the memory.
+
+@item interrupt
+A hardware facility that causes the CPU
+to suspend execution, save its status, and transfer control to a
+specific location.
+
+@item interrupt level
+A mask used to by the CPU to
+determine which pending interrupts should be serviced. If a
+pending interrupt is below the current interrupt level, then the
+CPU does not recognize that interrupt.
+
+@item Interrupt Service Routine
+An ISR is invoked by the
+CPU to process a pending interrupt.
+
+@item I/O
+An acronym for Input/Output.
+
+@item ISR
+An acronym for Interrupt Service Routine.
+
+@item kernel
+In this document, this term is used as a
+synonym for executive.
+
+@item list
+A data structure which allows for dynamic
+addition and removal of entries. It is not statically limited
+to a particular size.
+
+@item little endian
+A data representation scheme in which
+the bytes composing a numeric value are arranged such that the
+least significant byte is at the lowest address.
+
+@item local
+An object which was created with the LOCAL
+attribute and is accessible only on the node it was created and
+resides upon. In a single processor configuration, all objects
+are local.
+
+@item local operation
+The manipulation of an object which
+resides on the same node as the calling task.
+
+@item logical address
+An address used by an application.
+In a system without memory management, logical addresses will
+equal physical addresses.
+
+@item loosely-coupled
+A multiprocessor configuration
+where shared memory is not used for communication.
+
+@item major number
+The index of a device driver in the
+Device Driver Table.
+
+@item manager
+A group of related RTEMS' directives which
+provide access and control over resources.
+
+@item memory pool
+Used interchangeably with heap.
+
+@item message
+A sixteen byte entity used to communicate
+between tasks. Messages are sent to message queues and stored
+in message buffers.
+
+@item message buffer
+A block of memory used to store
+messages.
+
+@item message queue
+An RTEMS object used to synchronize
+and communicate between tasks by transporting messages between
+sending and receiving tasks.
+
+@item Message Queue Control Block
+A data structure
+associated with each message queue used by RTEMS to manage that
+message queue.
+
+@item minor number
+A numeric value passed to a device
+driver, the exact usage of which is driver dependent.
+
+@item mode
+An entry in a task's control block that is
+used to determine if the task allows preemption, timeslicing,
+processing of signals, and the interrupt disable level used by
+the task.
+
+@item MPCI
+An acronym for Multiprocessor Communications
+Interface Layer.
+
+@item multiprocessing
+The simultaneous execution of two
+or more processes by a multiple processor computer system.
+
+@item multiprocessor
+A computer with multiple CPUs
+available for executing applications.
+
+@item Multiprocessor Communications Interface Layer
+A set
+of user-provided routines which enable the nodes in a
+multiprocessor system to communicate with one another.
+
+@item Multiprocessor Configuration Table
+The data
+structure defining the characteristics of the multiprocessor
+target system with which RTEMS will communicate.
+
+@item multitasking
+The alternation of execution amongst a
+group of processes on a single CPU. A scheduling algorithm is
+used to determine which process executes at which time.
+
+@item mutual exclusion
+A term used to describe the act of
+preventing other tasks from accessing a resource simultaneously.
+
+@item nested
+A term used to describe an ASR that occurs
+during another ASR or an ISR that occurs during another ISR.
+
+@item node
+A term used to reference a processor running
+RTEMS in a multiprocessor system.
+
+@item non-existent
+The state occupied by an uncreated or
+deleted task.
+
+@item numeric coprocessor
+A component used in computer
+systems to enhance performance in mathematically intensive
+situations. It is typically viewed as a logical extension of
+the primary processor.
+
+@item object
+In this document, this term is used to refer
+collectively to tasks, timers, message queues, partitions,
+regions, semaphores, ports, and rate monotonic periods. All
+RTEMS objects have IDs and user-assigned names.
+
+@item object-oriented
+A term used to describe systems
+with common mechanisms for utilizing a variety of entities.
+Object-oriented systems shield the application from
+implementation details.
+
+@item operating system
+The software which controls all
+the computer's resources and provides the base upon which
+application programs can be written.
+
+@item overhead
+The portion of the CPUs processing power
+consumed by the operating system.
+
+@item packet
+A buffer which contains the messages passed
+between nodes in a multiprocessor system. A packet is the
+contents of an envelope.
+
+@item partition
+An RTEMS object which is used to allocate
+and deallocate fixed size blocks of memory from an dynamically
+specified area of memory.
+
+@item Partition Control Block
+A data structure associated
+with each partition used by RTEMS to manage that partition.
+
+@item pending
+A term used to describe a task blocked
+waiting for an event, message, semaphore, or signal.
+
+@item periodic task
+A task which must execute at regular
+intervals and comply with a hard deadline.
+
+@item physical address
+The actual hardware address of a
+resource.
+
+@item poll
+A mechanism used to determine if an event has
+occurred by periodically checking for a particular status.
+Typical events include arrival of data, completion of an action,
+and errors.
+
+@item pool
+A collection from which resources are
+allocated.
+
+@item portability
+A term used to describe the ease with
+which software can be rehosted on another computer.
+
+@item posting
+The act of sending an event, message,
+semaphore, or signal to a task.
+
+@item preempt
+The act of forcing a task to relinquish the
+processor and dispatching to another task.
+
+@item priority
+A mechanism used to represent the relative
+importance of an element in a set of items. RTEMS uses priority
+to determine which task should execute.
+
+@item priority inheritance
+An algorithm that calls for
+the lower priority task holding a resource to have its priority
+increased to that of the highest priority task blocked waiting
+for that resource. This avoids the problem of priority
+inversion.
+
+@item priority inversion
+A form of indefinite
+postponement which occurs when a high priority tasks requests
+access to shared resource currently allocated to low priority
+task. The high priority task must block until the low priority
+task releases the resource.
+
+@item processor utilization
+The percentage of processor
+time used by a task or a set of tasks.
+
+@item proxy
+An RTEMS control structure used to represent,
+on a remote node, a task which must block as part of a remote
+operation.
+
+@item Proxy Control Block
+A data structure associated
+with each proxy used by RTEMS to manage that proxy.
+
+@item PTCB
+An acronym for Partition Control Block.
+
+@item PXCB
+An acronym for Proxy Control Block.
+
+@item quantum
+The application defined unit of time in
+which the processor is allocated.
+
+@item queue
+Alternate term for message queue.
+
+@item QCB
+An acronym for Message Queue Control Block.
+
+@item ready
+A task occupies this state when it is
+available to be given control of the CPU.
+
+@item real-time
+A term used to describe systems which are
+characterized by requiring deterministic response times to
+external stimuli. The external stimuli require that the
+response occur at a precise time or the response is incorrect.
+
+@item reentrant
+A term used to describe routines which do
+not modify themselves or global variables.
+
+@item region
+An RTEMS object which is used to allocate
+and deallocate variable size blocks of memory from a dynamically
+specified area of memory.
+
+@item Region Control Block
+A data structure associated
+with each region used by RTEMS to manage that region.
+
+@item registers
+Registers are locations physically
+located within a component, typically used for device control or
+general purpose storage.
+
+@item remote
+Any object that does not reside on the local
+node.
+
+@item remote operation
+The manipulation of an object
+which does not reside on the same node as the calling task.
+
+@item return code
+Also known as error code or return
+value.
+
+@item resource
+A hardware or software entity to which
+access must be controlled.
+
+@item resume
+Removing a task from the suspend state. If
+the task's state is ready following a call to the task_resume
+directive, then the task is available for scheduling.
+
+@item return code
+A value returned by RTEMS directives to
+indicate the completion status of the directive.
+
+@item RNCB
+An acronym for Region Control Block.
+
+@item round-robin
+A task scheduling discipline in which
+tasks of equal priority are executed in the order in which they
+are made ready.
+
+@item RS-232
+A standard for serial communications.
+
+@item running
+The state of a rate monotonic timer while
+it is being used to delineate a period. The timer exits this
+state by either expiring or being canceled.
+
+@item schedule
+The process of choosing which task should
+next enter the executing state.
+
+@item schedulable
+A set of tasks which can be guaranteed
+to meet their deadlines based upon a specific scheduling
+algorithm.
+
+@item segments
+Variable sized memory blocks allocated
+from a region.
+
+@item semaphore
+An RTEMS object which is used to
+synchronize tasks and provide mutually exclusive access to
+resources.
+
+@item Semaphore Control Block
+A data structure associated
+with each semaphore used by RTEMS to manage that semaphore.
+
+@item shared memory
+Memory which is accessible by
+multiple nodes in a multiprocessor system.
+
+@item signal
+An RTEMS provided mechanism to communicate
+asynchronously with a task. Upon reception of a signal, the ASR
+of the receiving task will be invoked.
+
+@item signal set
+A thirty-two bit entity which is used to
+represent a task's collection of pending signals and the signals
+sent to a task.
+
+@item SMCB
+An acronym for Semaphore Control Block.
+
+@item soft real-time system
+A real-time system in which a
+missed deadline does not compromise the integrity of the system.
+
+@item sporadic task
+A task which executes at irregular
+intervals and must comply with a hard deadline. A minimum
+period of time between successive iterations of the task can be
+guaranteed.
+
+@item stack
+A data structure that is managed using a Last
+In First Out (LIFO) discipline. Each task has a stack
+associated with it which is used to store return information
+and local variables.
+
+@item status code
+Also known as error code or return
+value.
+
+@item suspend
+A term used to describe a task that is not
+competing for the CPU because it has had a task_suspend
+directive.
+
+@item synchronous
+Related in order or timing to other
+occurrences in the system.
+
+@item system call
+In this document, this is used as an
+alternate term for directive.
+
+@item target
+The system on which the application will
+ultimately execute.
+
+@item task
+A logically complete thread of execution. The
+CPU is allocated among the ready tasks.
+
+@item Task Control Block
+A data structure associated with
+each task used by RTEMS to manage that task.
+
+@item task switch
+Alternate terminology for context
+switch. Taking control of the processor from one task and given
+to another.
+
+@item TCB
+An acronym for Task Control Block.
+
+@item tick
+The basic unit of time used by RTEMS. It is a
+user-configurable number of microseconds. The current tick
+expires when the clock_tick directive is invoked.
+
+@item tightly-coupled
+A multiprocessor configuration
+system which communicates via shared memory.
+
+@item timeout
+An argument provided to a number of
+directives which determines the maximum length of time an
+application task is willing to wait to acquire the resource if
+it is not immediately available.
+
+@item timer
+An RTEMS object used to invoke subprograms at
+a later time.
+
+@item Timer Control Block
+A data structure associated
+with each timer used by RTEMS to manage that timer.
+
+@item timeslicing
+A task scheduling discipline in which
+tasks of equal priority are executed for a specific period of
+time before being preempted by another task.
+
+@item timeslice
+The application defined unit of time in
+which the processor is allocated.
+
+@item TMCB
+An acronym for Timer Control Block.
+
+@item transient overload
+A temporary rise in system
+activity which may cause deadlines to be missed. Rate Monotonic
+Scheduling can be used to determine if all deadlines will be met
+under transient overload.
+
+@item user extensions
+Software routines provided by the
+application to enhance the functionality of RTEMS.
+
+@item User Extension Table
+A table which contains the
+entry points for each user extensions.
+
+@item User Initialization Tasks Table
+A table which
+contains the information needed to create and start each of the
+user initialization tasks.
+
+@item user-provided
+Alternate term for user-supplied.
+This term is used to designate any software routines which must
+be written by the application designer.
+
+@item user-supplied
+Alternate term for user-provided.
+This term is used to designate any software routines which must
+be written by the application designer.
+
+@item vector
+Memory pointers used by the processor to
+fetch the address of routines which will handle various
+exceptions and interrupts.
+
+@item wait queue
+The list of tasks blocked pending the
+release of a particular resource. Message queues, regions, and
+semaphores have a wait queue associated with them.
+
+@item yield
+When a task voluntarily releases control of the processor.
+
+@end table
+