外文翻譯—電子信息的嵌入式程序下載和調(diào)試-電子信息-wenkub.com
2025-05-07 05:26 本頁面
【正文】 the following events are possible (also in bination): Event Timeout: the task Timer is set to the duration is specified with the os_wait function call. After the Timer decrements to zero, the task goes into Ready state. Interval: the time interval specified with os_wait is added to the task Timer value. After the Timer decrements to zero, the task goes into Ready state. Signal: the os_wait function was called with K_SIG and the task waits for Sig = 1. Sig status of the Signal bit that is assigned to this task. Timer value of the Timer that is assigned to this task. The Timer value decrements with every RTX system timer tick. If the Timer bees zero and the task is waiting for Timeout or Interval the task goes into Ready state. Stack value of the stack pointer (SP) that is used when this task is Running. RTX51 Tiny contains an efficient stack management that is explained in the RTX51 Tiny User’sGuide, Chapter 5: RTX51 Tiny, Stack Management. This manual provides detailed information about the Stack value. S 狀態(tài) 描述 Deleted Tasks that are not started are in the Deleted state. Ready Tasks that are waiting for execution are in the Ready state. After the currently Running task has finished processing, RTX starts the next task that is in the Ready state. Running The task currently being executed is in the Running state. Only one task is in the Running state at a time. Timeout Tasks that were interrupted by a roundrobin timeout are in the Timeout state. This state is equivalent to Ready。 signal from task or rest of this section uses RTX51 to refer to RTX51 Full and RTX51 between the two are stated where applicable. Introduction Many microcontroller applications require simultaneous execution of multiplejobs or tasks. For such applications, a realtime operating system (RTOS) allowsflexible scheduling of system resources (CPU, memory, etc.) to several implements a powerful RTOS that is easy to use. RTX51 works withall 8051 derivatives. You write and pile RTX51 programs using standard C constructs andpiling them with C51. Only a few deviations from standard C are requiredin order to specify the task ID and priority. RTX51 programs also require thatyou include the or header file. When you select in theμVision2 dialog Options for Target Target the operating system, the linker addsthe appropriate RTX51 library file. Single Task Program A standard C program starts execution with the main function. In an embeddedapplication, main is usually coded as an endless loop and can be thought of as asingle task that is executed continuously. For example: RoundRobin Task Switching RTX51 Tiny allows a quasiparallel, simultaneous execution of several task is executed for a predefined timeout period. A timeout suspends theexecution of a task and causes another task to be started. The following exampleuses this roundrobin task switching technique. Simple C Program using RTX51 RTX51 starts the program with task 0 (assigned to job0). The functionos_create_task marks task 1 (assigned to job1) as ready for execution. Thesetwo functions are simple count loops. After the timeout period has beenpleted, RTX51 interrupts job0 and begins execution of job1. This functioneven reaches the timeout and the system continues with job0. The os_wait Function The os_wait function provides a more efficient way to allocate the availableprocessor time to several tasks. os_wait interrupts the execution of the currenttask and waits for the specified event. During the time in which a task waits foran event, other tasks can be executed. Wait for Timeout RTX51 uses an 8051 timer in order to generate cyclic interrupts (timer ticks).The simplest event argument for os_wait is a timeout, where the currentlyexecuting task is interrupted for the specified number of timer ticks. Thefollowing uses timeouts for the time delay. Program with os_wait Function This program is similar to the previous example with the exception that job0 isinterrupted with os_wait after counter0 has been incremented. RTX51 waitsthree timer ticks until job0 is ready for execution again. During this time, job1 isexecuted. This function also calls os_wait with a timeout of 5 ticks. The result:counter0 is incremented every three ticks and counter1 is incremented every fivetimer ticks. Wait for Signal Another event for os_wait is a signal. Signals are used for task coordination: ifa task waits with os_wait until another task issues a signal. If a signal waspreviously sent, the task is immediately continued. Program with Wait for Signal. In this example, task
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