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Overview of I/O Memory Area Section 4-1
4-1-3 Clearing and Holding I/O Memory
Note 1. Mode changed from PROGRAM to RUN/MONITOR or vice-versa.
2. The PLC Setup’s IOM Hold Bit Status at Startup setting determines wheth-
er the IOM Hold Bit’s status is held or cleared when the PLC is turned ON.
4-1-4 Hot Start/Hot Stop Functions
Operating Mode Changes
Hot Start
Turn ON the IOM Hold Bit to retain all data* in I/O memory when the CPU Unit
is switched from PROGRAM mode to RUN/MONITOR mode to start program
execution.
Hot Stop
When the IOM Hold Bit is ON, all data* in I/O memory will also be retained
when the CPU Unit is switched from RUN or MONITOR mode to PROGRAM
mode to stop program execution.
Area
Mode changed
1
Fatal error generated
PLC power turned ON
Execution of FALS Other fatal errors PLC Setup set to
clear IOM Hold Bit
status
2
PLC Setup set to
hold IOM Hold Bit
status
2
IOM Hold
Bit OFF
IOM Hold
Bit ON
IOM Hold
Bit OFF
IOM Hold
Bit ON
IOM Hold
Bit OFF
IOM Hold
Bit ON
IOM Hold
Bit OFF
IOM Hold
Bit ON
IOM Hold
Bit OFF
IOM Hold
Bit ON
CIO
Area
I/O Area Cleared Retained Retained Retained Cleared Retained Cleared Cleared Cleared Retained
Built-in Analog I/O Areas
(XA CPU Units only)
Data Link Area
CPU Bus Unit Area
Special I/O Unit Area
Serial PC Link Area
DeviceNet Area
Internal I/O Area
Work Area (W) Cleared Retained Retained Retained Cleared Retained Cleared Cleared Cleared Retained
Holding Area (H) Retained Retained Retained Retained Retained Retained Retained Retained Retained Retained
Auxiliary Area (A) Status treatment depends on address.
Data Memory Area (D) Retained Retained Retained Retained Retained Retained Retained Retained Retained Retained
Timer Completion Flags (T) Cleared Retained Retained Retained Cleared Retained Cleared Cleared Cleared Retained
Timer PVs (T) Cleared Retained Retained Retained Cleared Retained Cleared Cleared Cleared Retained
Counter Completion Flags (C) Retained Retained Retained Retained Retained Retained Retained Retained Retained Retained
Counter PVs (C) Retained Retained Retained Retained Retained Retained Retained Retained Retained Retained
Task Flags (TK) Cleared Cleared Retained Retained Cleared Cleared Cleared Cleared Cleared Cleared
Index Registers (IR) Cleared Retained Retained Retained Cleared Retained Cleared Cleared Cleared Retained
Data Registers (DR) Cleared Retained Retained Retained Cleared Retained Cleared Cleared Cleared Retained
PROGRAM
Retain
I/O memory
CIO and
other areas
MONITOR or RUN
PROGRAM
Retain
MONITOR or RUN
I/O memory
CIO and
other areas