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I/O Memory Areas Section 9-2
Work Area (WR) Words in the Work Area can be used only in the program; they cannot be
used for I/O exchange with external I/O terminals. No new functions will be
assigned to this area in future versions of CJ-series PLCs, so use this area for
work words and bits before any words in the CIO Area.
Holding Area (HR) Words in the Holding Area can be used only in the program. These words
retain their content when the PLC is turned on or the operating mode is
switched between PROGRAM mode and RUN or MONITOR mode.
Note The Function Block Holding Area words are allocated from H512 to H1535.
These words can be used only for the function block instance area (internally
allocated variable area). These words cannot be specified as instruction oper-
ands in the user program.
Auxiliary Area (AR) The Auxiliary Area contains flags and control bits used to monitor and control
PLC operation. This area is divided into two parts: A000 to A447 are read-
only and A448 to A959 can be read or written. Refer to
9-11 Auxiliary Area for
details on the Auxiliary Area.
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.
Temporary Relay Area
(TR)
The TR Area contains bits that record the ON/OFF status of program
branches. The TR bits are used with mnemonics only.
15
W511
Word Bit
15
H511
Word Bit
A447
A448
A959
15
Read-write area
Read-only area
Word
Bit
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