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Overview of I/O Memory Area Section 4-1
CPU Bus Unit Area
These words are used when connecting the CJ-series CPU Bus Units. Words
that aren’t used by CPU Bus Units may be used in programming.
Special I/O Unit Area
These words are used when connecting the CJ-series Special I/O Units.
Words that aren’t used by Special I/O Units may be used in programming.
Serial PLC Link Area
These words are allocated for use for data links (Serial PLC Links) with other
CP1H CPU Units or CJ1M CPU Units. Addresses not used for Serial PLC
Links can be used in programming.
DeviceNet Area
These words are allocated to slaves for remote I/O communications for CJ-
series DeviceNet Units. Allocations are fixed and cannot be changed. Words
that aren’t used by DeviceNet devices can be used in programming.
Internal I/O Area
These words can be used in programming; they cannot be used for I/O
exchange with external I/O terminals. Be sure to use the work words provided
in the Work Area before using words in the Internal I/O Area or other unused
words in the CIO Area. It is possible that these words will be assigned to new
functions in future versions of the CPU Units. The parts of the CIO Area that
are labelled “Not used” are functionally identical to the Internal I/O Area.
Work Area (W) Words in the Work Area can be used in programming; they cannot be used for
I/O exchange with external I/O terminals. Use this area for work words and
bits before any words in the CIO Area.
Note These words should be used first in programming be assigned to new func-
tions in future versions of CP1H CPU Units.
Holding Area (H) Words in the Holding Area can be used in programming. 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 H512 to H1535 are used as a Function Block Holding Area. These words can
be used only for function block instances (internally allocated variable area).
These words cannot be specified as instruction operands in the user program.
15
W511
Word Bit
15
H511
Word Bit
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