8 I/O Allocations and Unit Settings
8-26
CJ2 CPU Unit Software User’s Manual
Precautions for Correct UsePrecautions for Correct Use
IORF(097), FIORF(225), IORD (222), and IOWR(223) can be executed for Special I/O Units
from interrupt tasks. When doing so, always disable the Special I/O Unit's cyclic refreshing in the
PLC Setup. If cyclic refreshing is not disabled and either of the following processes is executed in
an interrupt task, a non-fatal error will occur and the Duplicate Refresh Error Flag (A402.13) will
turn ON.
• I/O refreshing is executed using IORF(097) or FIORF(225) for the same Special I/O Unit.
• Data is read or written to or from the memory area using IORD (222) or IOWR(223) for the
same Special I/O Unit.
Whenever disabling a Special I/O Unit's cyclic refreshing, be sure that the I/O for that Unit is
refreshed with IORF(097) or FIORF(225) in the program at least every 11 seconds during opera-
tion. A CPU Unit service monitoring error will occur in the Special I/O Unit if it is not refreshed
every 11 seconds.
z CPU Bus Unit Area (I/O Refreshing)
Data is exchanged each cycle during I/O refreshing of the CPU Bus Unit Area. Basically, 25 words
are allocated to each CPU Bus Unit based on its unit number setting. The number of words actually
used by the CPU Bus Unit varies.
The Special I/O Unit Area ranges from CIO 1500 to CIO 1899 (25 words × 16 Units).
Note The CPU BUS I/O REFRESH instruction (DLNK(226)) can be executed in the ladder program to refresh the
CIO Area words allocated to the CPU Bus Unit of a specified unit number.
z Transfer of Words Allocated in the DM Area
One hundred words are allocated to each Unit according to the unit number.
Note These words are not used for all models of CPU Bus Unit.
DM Area Words for the CPU Bus Units: D30000 to D31599 (100 words × 16 Units)
The contents of these words are transferred at the following times. Which transfers actually take
place depends on the model of the Unit.
• Data transferred when the PLC is turned ON.
• Data transferred each cycle.
• Data transferred when necessary.
Note The CPU BUS I/O REFRESH instruction (DLNK(226)) can be executed in the ladder program to refresh the
DM Area words allocated to the CPU Bus Unit of a specified unit number.
Some models transfer data in both directions, from the DM Area to the Unit and from the Unit to the
DM Area. Refer to the Unit's operation manual for details on data transfers.
CPU Bus Units
CPU Bus Unit Area
25 words/Unit
CPU Bus Unit
CPU Unit
Trans-
ferred in
I/O
refreshing
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