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3. Instructions
• If a holding bit is used for B, the bit status will be retained even during a power interruption.
KEEP(011) can thus be used to program bits that will maintain status after restarting the PLC
following a power interruption. An example of this that can be used to produce a warning display
following a system shutdown for an emergency situation is shown below.
0.02
0.03
Indicates
emergency
situation
0.04
0.05
Reset input
H0.00
• The status of I/O Area bits can be retained in the event of a power interruption by turning ON the IOM
Hold Bit and setting IOM Hold Bit Hold in the PLC Setup. In this case, I/O Area bits used in
KEEP(011) will maintain status after restarting the PLC following a power interruption, just like
holding bits. Be sure to restart the PLC after changing the PLC Setup; otherwise the new settings will
not be used.
Precautions
• If S and R are ON simultaneously, the reset
input takes precedence.
• The set input (S) cannot be received while
R is ON.
• Never use an input bit in a normally closed
condition on the reset (R) for KEEP(011)
when the input device uses an AC power
supply. The delay in shutting down the
PLC's DC power supply (relative to the AC
power supply to the input device) can cause
the operand bit of KEEP(011) to be reset.
This situation is shown on the right.
162
H0.00
0.03
Activates
warning
display
Set
Reset
Status of C
Input Unit
A
CS/CJ/NSJ Series Instructions Reference Manual (W474)
Set
Reset
Status of C
NEVER
A
S
KEEP
120000
R
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