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Special I/O Unit Area Section 4-6
4-6 Special I/O Unit Area
The Special I/O Unit Area contains 960 words with addresses ranging from
CIO 2000 to CIO 2959. Words in the Special I/O Unit Area are allocated to
transfer data, such as the operating status of the Unit. Each Unit is allocated
10 words based on its unit number setting.
Data is exchanged with Special I/O Units once each cycle during I/O refresh-
ing, which occurs after program execution. The words can also be refreshed
with IORF(097).
Each Special I/O Unit is allocated 25 words based on its unit number, as
shown in the following table.
Words in the Special I/O Unit Area that are not allocated to Special I/O Units
can be used in programming.
Forcing Bit Status Bits in the Special I/O Unit Area can be force-set and force-reset.
Special I/O Unit Area
Initialization
The contents of the Special I/O Unit Area will be cleared in the following
cases:
1. When the operating mode is changed from PROGRAM mode to
RUN/MONITOR mode or vice-versa and the IOM Hold Bit is OFF
2. When the power is cycled
3. When the Special I/O Unit Area is cleared from the CX-Programmer
4. When PLC operation is stopped when a fatal error other than an
FALS(007) error occurs (The contents of the Special I/O Unit Area will be
retained when FALS(007) is executed.
Unit number Allocated words
0 CIO 2000 to CIO 2009
1 CIO 2010 to CIO 2019
2 CIO 2020 to CIO 2029
3 CIO 2030 to CIO 2039
95 CIO 2950 to CIO 2959
CPU Bus Unit Area
(10 words/Unit)
CPU Bus UnitCPU Unit
I/O
refreshing or
IORF command
CJ-series Special I/O Unit
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