T-Kernel Specification (1.B0.02)

56 CHAPTER 4. T-KERNEL/OS FUNCTIONS
tk can wup
Cancel Wakeup Task
[C Language Interface]
INT wupcnt = tk_can_wup ( ID tskid ) ;
[Parameters]
ID tskid Task ID
[Return Parameters]
INT wupcnt Number of queued wakeup requests
or Error Code
[Error Codes]
E OK
E ID
E NOEXS
E OBJ
Normal completion
Invalid ID number (tskid is invalid or cannot be used)
Object does not exist (the task designated in tskid does not exist)
Invalid object state (called for a task in DORMANT state)
[Description]
Passes in the return parameter the wakeup request queuing count (wupcnt) for the task designated in
tskid, at the same time canceling all wakeup requests. That is, this system call clears the wakeup
request queuing count (wupcnt) to 0 for the designated task.
The invoking task can be designated by setting tskid = TSK SELF = 0. Note, however, that when a
system call is issued from a task-independent portion and tskid = TSK SELF = 0 is designated, error
code E ID is returned.
[Additional Notes]
When processing is performed that involves cyclic wakeup of a task, this system call is used to determine
whether the processing was completed within the allotted time. Before processing of a prior wakeup
request is completed and tk slp tsk is called, the task monitoring this calls tk can wup. If wupcnt in
the return parameter is 1 or above, this means the previous wakeup request was not processed within
the allotted time. A processing delay or other measure can then be taken accordingly.
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T-Kernel 1.B0.02