
2. TASK CONTROL FUNCTION
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PMC CONTROL SOFTWARE
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The stack size to be used by each task is specified. The stack size must
be calculated taking into consideration the size used when a function is
called. (See Appendix B)
The task level at which each activated task starts running is specified. A
task level from 10 to 99 can be set. Level 10 has the highest priority and
level 99 has the lowest priority.
If a task level is set to –1, the task is given the priority just below that for
first-level and second-level ladder programs.
Task level –1 can be specified for only one task; this specification is
applicable only to a program having a short processing time
(approximately 1 ms). In addition, the execution time for first-level and
second-level ladder programs must be 5 ms or shorter (LADDER EXEC
= 100% or less).
CAUTION
The first and second Ladder levels are not provided for the
C language function of the Series 16i/18i/21i. If the
processing time required for a highest–priority task is long,
the PMC screen display or key input may be disabled.
CAUTION
1 If the execution time for first-level and second-level ladder
programs is longer than 5 ms or the processing time of the
highest-priority task is long, the PMC screen display may
slow down remarkably, or other C programs may become
inoperable.
2 A highest-priority task can be specified only when link
control data is created. It cannot be specified at program
run time. Once the priority of that task is decreased using
a system call os_chng_pri (mentioned later), the priority
cannot be increased to the highest again while the program
is running.
Task names are used within the system. The character strings set here are
displayed as task names on the user diagnosis screen. Set a task name with
eight ASCII characters (uppercase alphanumeric characters).
NOTE
GDT and BUILDER are words reversed by Intel. Refer to
the “Intel386 Family System Builder” provided by Intel.
2.4.7
Task Stack Size
2.4.8
Task Level When a
Task is Activated
2.4.9
Highest-priority Task
2.4.10
Task Name