Omron CJ - PROGRAMMING MANUAL 08-2008 Programming Manual page 306

Cycle Time/High-speed Processing
Disabling Special I/O Unit Cyclic Refreshing
Note
268
be sure that refreshing has been completed normally.
Execution condition
2. IORF(097) is used to refresh data for Basic I/O Units and Special I/O Units.
DLNK(226) is used to refresh CPU Bus Units (CIO and DM Area words al-
located to the Units and special data for the Units).
Ten words in the Special I/O Unit Area (CIO 2000 to CIO 2959) are allocated
to each Special I/O Unit based on the unit number set on the front of the Unit.
Data is refreshed between this area and the CPU Unit each cycle during I/O
refreshing, after all of the instructions in the executable tasks have been exe-
cuted.
If many Special I/O Units are installed, the cycle time may become too long
due to the time required for I/O refreshing of the Special I/O Units. To reduce
the I/O refreshing time, cyclic refreshing can be disabled for individual Special
I/O Units in the PLC Setup.
Note If the I/O refreshing interval is too short, the Unit's internal processing may not
be able to keep pace, the Special I/O Unit Error Flag (A40206) will be turned
ON, and the Special I/O Unit will not operate properly.
In this case, the cycle time can be extended by setting a minimum cycle time
in the PLC Setup, or the Special I/O Unit's cyclic I/O refreshing can be dis-
abled in the PLC Setup.
When a Special I/O Unit's cyclic refreshing has been disabled, the Unit's data
will not be refreshed unless the IORF(097) or FIORF(225) (CJ1-H-R only)
instruction is executed for the Unit in the ladder program.
1. If an IORF(097), FIORF(225) (CJ1-H-R only), IORD(222), or IOWR(223)
instruction is being executed for a Special I/O Unit in an interrupt task, al-
ways disable cyclic refreshing for that Special I/O Unit in the PLC Setup.
An interrupt task error will occur if a Special I/O Unit is being refreshed by
cyclic refreshing, and an IORF(097), FIORF(225) (CJ1-H-R only),
IORD(222), or IOWR(223) instruction is executed for that Special I/O Unit.
2. When you want to disable a Special I/O Unit's cyclic refreshing and refresh
the Unit's I/O data only when necessary, execute the FIORF(225) instruc-
tion (CJ1-H-R only) for that Unit.
PLC Setup
When using the CX-Programmer, make the settings on the SIOU Refresh Tab
Page.
Refreshes data for the CPU
DLNK
Bus Unit with unit number 0.
&0
= Flag
Bit "a"
Turns ON bit "a" if data
refreshing fails, enabling the
problem to be detected.
Section 6-1