3 CPU Unit Operation
3-8
CP1E CPU Unit Software User’s Manual(W480)
For E-type or N/NA-type (without a battery) CPU Units, the held areas in I/O memory (i.e., Holding
Area, Counter Present Values, Counter Completion Flags, and DM Area) may be unstable when the
power supply is turned ON. Therefore, use one of the following ways to clear these areas.
Clearing All Held Areas to Zero at Startup
Select the Clear retained memory area (HR/DM/CNT) Check Box in the PLC Settings.
Note If the Restore D0- from backup memory Check Box is selected, only the specified words in the DM Area will
be restored from the built-in EEPROM backup memory when the power supply is turned ON.
Initializing Specific Held Areas at Startup
Write the following type of ladder programming.
3-2-4 Initializing I/O Memory at Startup
#0000
BSET
D100
D2047
#0000
BSET
H10
D49
C0
CNR
C255
P_First_Cycle
Example
First Cycle Flag
(A200.11)
C0 to C255 are cleared
to Zero
H10 to H49 are cleared
to Zero
D100 to D2047 are cleared
to Zero