Omron CP1H CPU Operation Manual page 179

Overview of I/O Memory Area
Work Area (W)
Note
Holding Area (H)
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.
Note The CPM1A-DRT21 CPM1A DeviceNet I/O Link Unit uses the I/O
area instead of the DeviceNet Area.
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.
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.
Word
15
W511
These words should be used first in programming be assigned to new func-
tions in future versions of CP1H CPU Units.
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.
Word
15
H511
Bit
Bit
Section 4-1
145