3-11
3 CPU Unit Operation
CJ2 CPU Unit Software User’s Manual
3-2 CPU Unit Operating Modes
3
3-2-3 Changing the Operating Mode
Some parts of I/O memory, such as the CIO Area and Work area, will be cleared when the operating
mode is changed between RUN or MONITOR mode and PROGRAM mode. These are called non-hold-
ing areas. To hold the contents of these areas when the operating mode is changed, turn ON the IOM
Hold Bit (A500.12) in the Auxiliary Area
*1 Memory is cleared on if the IOM Hold Bit is OFF. If it is ON, data will be held as follows:
*2 The IOM Hold Bit (A500.12) will be turned OFF when a power interruption is reset. To retain the status, select
the IOM Hold Bit Check Box in the Startup Hold Settings Tab Page of the PLC Setup using the CX-Program-
mer, and then transfer the PLC Setup.
*3 The Task Flags will be cleared regardless of the status of IOM Hold Bit (A500.12).
Memory Status after Mode Changes and Power Interruptions
Mode change Non-holding areas Holding Areas
• I/O Area
• Data Link Area
• CPU Bus Unit Area
• Special I/O Unit Area
• Work Area
• Timer PV and Completion Flags
• Index Registers
• Data Registers
• Task Flags
(Auxiliary Area bits/words are held or not
held depending on the address.)
• HR Area
•DM Area
•EM Area
• Counter PV and Completion Flags
(Auxiliary Area bits/words are held or not
held depending on the address.)
RUN or MONITOR to
PROGRAM
Cleared
*1
Held
PROGRAM to RUN
or MONITOR
RUN to MONITOR or
MONITOR to RUN
Held Held
Power interruption
reset
*2
Cleared
*3
Held
I/O Memory
Hold Bit sta-
tus (A500.12)
I/O Memory Output bits allocated to Output Units
Mode
changed
between
PROGRAM
and
RUN/MONI-
TOR
Fatal error Mode
changed
between
PROGRAM
and
RUN/MONI-
TOR
Fatal error
Fatal error
other than
FALS
FALS
executed
Fatal error
other than
FALS
FALS
executed
OFF Cleared Cleared Held OFF OFF OFF
ON
Held Held Held Held OFF:
Values in the I/O memory in
the CPU Unit will be held when
a fatal error occurs, but the
outputs from Basic Output
Units will turn OFF.
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