Omron CJ - 09-2009 Operation Manual page 420

I/O Memory Areas
372
Rack addresses in the I/O table. The settings range for the first Rack ad-
dresses is from CIO 0000 to CIO 0900.
2. The parts of the CIO Area that are labelled "Not used" may be used in pro-
gramming as work bits. In the future, however, unused CIO Area bits may
be used when expanding functions. Always use Work Area bits first.
I/O Area
These words are allocated to external I/O terminals on Basic I/O Units. Words
that aren't allocated to external I/O terminals may be used only in the pro-
gram.
Data Link Area
These words are used for data links in Controller Link Networks. Words that
aren't used in data links may be used only in the program.
CPU Bus Unit Area
These words are allocated to CPU Bus Units to transfer status information.
Each Unit is allocated 25 words and up to 16 Units (with unit numbers 0 to 15)
can be used. Words that aren't used by CPU Bus Units may be used only in
the program.
Special I/O Unit Area
These words are allocated to Special I/O Units. Each Unit is allocated 10
words and up to 96 Units (unit numbers 0 to 95) can be used).
Words that aren't used by Special I/O Units may be used only in the program.
Built-in I/O Area (CJ1M CPU Units with Built-in I/O Only)
These words are allocated to the CPU Unit's built-in I/O port. Allocations are
fixed and cannot be changed. This area can be used only by CJ1M CPU Units
with the built-in I/O. Other CPU Units can be programmed only as described
below under "Internal I/O Area."
Serial PLC Link Area
These words are allocated for use with the Serial PLC Link, for data links with
other PLCs. Addresses not used for Serial PLC Link can be used only in the
program, the same as the Work Area.
DeviceNet Area
These words are allocated to Slaves for DeviceNet Remote I/O Communica-
tions. Allocations are fixed and cannot be changed. Words that aren't used by
DeviceNet devices can be used only in the program.
Internal I/O Area
These words can be used only in the program; 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 (WR) before allocating 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 CJ-series CPU Units, so the
program may have to be changed before being used in a new CJ-series PLC if
CIO Area words are used as work words in the program.
Section 9-2