Omron CP1H CPU UNITS - PROGRAMMING 05-2007, Operation Manual

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Overview of I/O Memory Area
Section 4-1
Note *The following areas of I/O memory will be cleared during mode changes
(between PROGRAM and RUN/MONITOR) unless the IOM Hold Bit is ON:
the CIO Area (I/O Area, Data Link Area, CPU Bus Unit Area, Special I/O Unit
Area, DeviceNet (CompoBus/D) Area, and Internal I/O Areas), Work Area,
Timer Completion Flags, and Timer PVs.
Auxiliary Area Flags and Words
When the IOM Hold Bit is ON, all outputs from Output Units will be maintained
when program execution stops. When the program starts again, outputs will
have the same status that they had before the program was stopped and
instructions will be executed. (When the IOM Hold Bit is OFF, instructions will
be executed after the outputs have been cleared.)
PLC Power ON In order for all data* in I/O memory to be retained when the PLC is turned ON,
the IOM Hold Bit must be ON and it must be protected in the PLC Setup using
the
IOM Hold Bit Status at Startup parameter.
Auxiliary Area Flags and Words
PLC Setup
Name Address Description
IOM Hold Bit A500.12 Specifies whether the I/O memory will be retained or not
when the CPU Unit operating mode is changed
(between PROGRAM and RUN/MONITOR) or when the
power is cycled.
OFF: I/O memory is cleared to 0 when the operating
mode is changed.
ON: I/O memory is retained when the operating mode
is changed between PROGRAM and RUN or
MONITOR.
Name Address Description
IOM Hold Bit A500.12 Specifies whether the I/O memory will be retained or
not when the CPU Unit operating mode is changed
(between PROGRAM and RUN/MONITOR) or when
the power is cycled.
OFF: I/O memory is cleared to 0 when the operating
mode is changed.
ON: I/O memory is retained when the operating
mode is changed between PROGRAM and
RUN or MONITOR.
Name Description Setting Default
IOM Hold
Bit Status
at Startup To retain all data in I/O
memory when the PLC
is turned ON, set the
IOM Hold Bit at startup
parameter to hold the
status of the I/O Hold Bit.
OFF: The IOM Hold Bit is cleared
to 0 when power is cycled.
ON: The status of the IOM Hold
Bit is retained when power is
cycled.
OFF
(Cleared)
Retained
Power ON
I/O memory
CIO and
other areas