4.
AXCPU
/MELSEC-A
49.2
Power
failure compmrrtion for device data in
tho
Ax
(LATCH
function)
Each individual device of the A2CCPU is reset when the A2CCPU is
powered up. Device will
be
cleared when
a
momentary power
failure occurs for more than 20
msec.
After being reset or cleared,
all
device data is reset to the default values (OFF for bit devices
and
0
for word devices).
The latch function retains
the
device data
in
the event that the
A2CCPU is reset by turning on
the
power or pressing using the
RUN switch or
a
momentary power failure occurs for more than 20
msec.
Sequence program operation is the same regardless whether
the
data is latched or not.
(1
)
Applications
The latch function is used to continue the control by retaining
data such
as
the number of completed products, the number
of defective products, and
the
addresses should a momentary
power failure occur for more than 20 msec.
(2)
Latch devices and latch range setting
(a)
The devices whose data can be latched are listed below:
1) Latch relay (LO to L2047)
2)
Link relay
(BO
to B3FF)
3) Timer
(TO
to T255)
4) Counter
(CO
to C255)
5)
Data register (DO to D1023)
6)
Link register (WO to W3FF)
(b) The latch range
is
set
in the peripheral parameters per
device.
I
c
-i
a
I
3
U
Y
n
d
Device
date within the
htch
range
is
backed
by
the battery
(ABBAT)
installed
to
the
A2C.
(a) The
battery
is
required
even
when operation
is
per-
formed
using
a
ROM
which
stores
the
sequence
program.
(b)
Device
data
within the
latch
range
b
corrupted
if
the
battery connector
is
dmng.(isd from
the
A2C
when
the
A2C
is being turned
off.
J
1
I
U
i
4-20
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18wJeE23e-A
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