61
Using Tasks Section 2-2
• Other words and bits in I/O Memory are shared by all tasks. CIO 10.00 for
example is the same bit for both cyclic task 1 and cyclic task 2. Therefore,
be very careful in programming any time I/O memory areas other than the
IR and DR Areas are used because values changed with one task will be
used by other tasks.
Note IR and DR values are not set when interrupt tasks (including extra
cyclic tasks) are started. If IR and DR are used in an interrupt task,
these values must be set by the MOVR/MOVRW (MOVE TO REG-
ISTER and MOVE TIMER/COUNTER PV TO REGISTER) instruc-
tions within the interrupt task. After the interrupt task has been
executed, IR and DR will return to their values prior to the interrupt
automatically.
Relationship of Tasks to
Timer Operation
Timer present values for TIM, TIMX, TIMH, TIMHX, TMHH, TMHHX, TIMW,
TIMWX, TMHW, and TMHWX programmed for timer numbers T0000 to
T0015 will be updated even if the task is switched or if the task containing the
timer is changed to Standby status or back to READY status.
If the task containing TIM goes to Standby status and is the returned to
READY status, the Completion Flag will be turned ON if the TIM instruction is
executed when the present value is 0. (Completion Flags for timers are
updated only when the instruction is executed.) If the TIM instruction is exe-
cuted when the present value is not yet 0, the present value will continue to be
updated just as it was while the task was in READY status.
• The present values for timers programmed with timer numbers T0016 to
T4095 will be maintained when the task is in Standby status.
Relationship of Tasks to
Condition Flags
All Condition Flags will be cleared before execution of each task. Therefore
Condition Flag status at the end of task 1 cannot be read in task 2. CCS(282)
and CCL(283) can be used to read Condition Flag status from another part of
the program, e.g., from another task.
2-2-2 Task Instruction Limitations
Instructions Required
in the Same Task
The following instructions must be placed within the same task. Any attempt
to split instructions between two tasks will cause the ER Flag to turn ON and
the instructions will not be executed.
I/O memory Relationship to tasks
CIO, Auxiliary, Data Memory and all other
memory areas except the IR and DR Areas.
Shared with other tasks.
Index registers (IR) and data registers (DR)
(See note.)
Used separately for each task.
Mnemonic Instruction
JMP/JME JUMP/JUMP END
CJP/JME CONDITIONAL JUMP/JUMP END
CJPN/JME CONDITIONAL JUMP NOT/CONDITIONAL JUMP END
JMP0/JME0 MULTIPLE JUMP/JUMP END
FOR/NEXT FOR/NEXT
IL/ILC INTERLOCK/INTERLOCK CLEAR
SBS/SBN/RET SUBROUTINE CALL/SUBROUTINE ENTRY/SUBROUTINE
RETURN
MCRO/SBN/RET MACRO/SUBROUTINE ENTRY/SUBROUTINE RETURN
BPRG/BEND BLOCK PROGRAM BEGIN/BLOCK PROGRAM END
STEP /SNXT STEP DEFINE
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