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Auxiliary Area Section 9-11
3. The Function Block Holding Area words are allocated from H512 to H1535.
These words can be used only for the function block instance area (inter-
nally allocated variable area). These words cannot be specified as instruc-
tion operands in the user program.
Precautions When a Holding Area bit is used in a KEEP(011) instruction, never use a nor-
mally closed condition for the reset input if the input device uses an AC power
supply. When the power supply goes OFF or is temporarily interrupted, the
input will go OFF before the PLC’s internal power supply and the Holding Area
bit will be reset.
Instead, use a configuration like the one shown below.
There are no restrictions in the order of using bit address or in the number of
N.C. or N.O. conditions that can be programmed.
9-11 Auxiliary Area
The Auxiliary Area contains 960 words with addresses ranging from A000 to
A959). These words are preassigned as flags and control bits to monitor and
control operation.
A000 through A447 are read-only, but A448 through A959 can be read or writ-
ten from the program or a Programming Device.
Forcing Bit Status
Bits in the Auxiliary Area cannot be force-set and force-reset continuously.
Writing Auxiliary Area Data
The following operations can be performed from a Programming Device to
write data in the Auxiliary Area.
• Using the CX-Programmer: Online set/reset (not force-set/force-reset),
changing present values when monitoring programming addresses (set
values dialog box), or transferring data to the PLC after editing the PLC
data tables. Refer to the CX-Programmer Operation Manual (W414).
• Using a Programming Console: Temporarily force-setting/force-resetting
bits from the Bit/Word Monitor or the 3-word Monitor operation (refer to
the Programming Console Operation Manual (W341)).
Note There is a possibility that a function will be assigned to an undefined Auxiliary
Area word or bit in a future upgrade of the CPU Units. Do not use undefined
words or bits in the Auxiliary Area as work words or bits in the user program.
Input
Unit
Set input
Reset input
Input
Unit
Set input
Reset input
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