IAR PowerPac RTOS User Guide

GlossaryActive TaskCooperativemultitaskingCounting semaphoreCPUCritical regionEventISRMailboxMessageMultitaskingNMIPreemptive multitaskingProcessorPriorityOnly one task can execute at any given time. The task that is currently executing is calledthe active task.A scheduling system in which each task is allowed to run until it gives up the CPU; an ISRcan make a higher priority task ready, but the interrupted task will be returned to andfinished first.A type of semaphore that keeps track of multiple resources. Used when a task must waitfor something that can be signaled more than once.Central Processing Unit. The "brain" of a microcontroller; the part of a processor thatcarries out instructions.A section of code which must be executed without interruption.A message sent to a single, specified task that something has occurred. The task thenbecomes ready.Interrupt Service Routine. The routine is called automatically by the processor when aninterrupt is acknowledged. ISRs must preserve the entire context of a task (all registers).A data buffer managed by the RTOS, used for sending messages to a task or interrupthandler.An item of data (sent to a mailbox, queue, or other container for data).The execution of multiple software routines independently of one another. The OS dividesthe processor's time so that the different routines (tasks) appear to be happeningsimultaneously.Non-Maskable Interrupt. An interrupt that cannot be masked (disabled) by software.Example: Watchdog timer-interrupt.A scheduling system in which the highest priority task that is ready will always be executed.If an ISR makes a higher priority task ready, that task will be executed before theinterrupted task is returned to.Short for microprocessor. The CPU core of a controllerThe relative importance of one task to another. Every task in an RTOS has a priority.Priority inversionQueueA situation in which a high priority task is delayed while it waits for access to a sharedresource which is in use by a lower priority task. The lower priority task temporarily getsthe highest priority until it releases the resource.Like a mailbox, but used for sending larger messages, or messages of individual size, to atask or an interrupt handler.PPRTOS-2 143