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Holding Area Section 9-10
Work Area Initialization The contents of the Work Area will be cleared in the following cases:
1,2,3... 1. The operating mode is changed from PROGRAM to RUN or MONITOR
mode or vice-versa and the IOM Hold Bit is OFF.
2. The PLC’s power supply is cycled and the IOM Hold Bit is OFF or not pro-
tected in the PLC Setup.
3. The Work Area is cleared from a Programming Device.
4. PLC operation is stopped when a fatal error other than an FALS(007) error
occurs. (The contents of the Work Area will be retained when FALS(007)
is executed.)
IOM Hold Bit Operation If the IOM Hold BIt (A50012) is ON, the contents of the Work Area won’t be
cleared when a fatal error occurs or the operating mode is changed from
PROGRAM mode to RUN/MONITOR mode or vice-versa.
If the IOM Hold BIt (A50012) is ON and the PLC Setup’s “IOM Hold Bit Status
at Startup” setting is set to protect the IOM Hold Bit, the contents of the Work
Area won’t be cleared when the PLC’s power supply is cycled.
9-10 Holding Area
The Holding Area contains 512 words with addresses ranging from H000 to
H511 (bits H00000 to H51115). These words can be used only in the pro-
gram.
Holding Area bits can be used in any order in the program and can be used as
normally open or normally closed conditions as often as necessary.
Holding Area Initialization Data in the Holding Area is not cleared when the PLC’s power supply is cycled
or the PLC’s operating mode is changed from PROGRAM mode to RUN or
MONITOR mode or vice-versa.
A Holding Area bit will be cleared if it is programmed between IL(002) and
ILC(003) and the execution condition for IL(002) is OFF. To keep a bit ON
even when the execution condition for IL(002) is OFF, turn ON the bit with the
SET instruction just before IL(002).
Self-maintaining Bits When a self-maintaining bit is programmed with a Holding Area bit, the self-
maintaining bit won’t be cleared even when the power is reset.
Note 1. If a Holding Area bit is not used for the self-maintaining bit, the bit will be
turned OFF and the self-maintaining bit will be cleared when the power is
reset.
2. If a Holding Area bit is used but not programmed as a self-maintaining bit
as in the following diagram, the bit will be turned OFF by execution condi-
tion A when the power is reset.
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