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FX Series Programmable Controllers
10.6
Using Battery Backed Devices
For Maximum Advantage
Battery backed devices retain their status during a PLC power down. These devices can be
used for maximum advantage by allowing the PLC to continue from its last operation status
just before the power failure.
For example: A table traverse system is operating, moving alternatively between two limit
switches. If a PLC power failure occurs during the traversing the machine will stop.
Ideally, once the PLC regains its power the system should continue from where it left off, i.e. if
the movement direction was to the left before the power down, it should continue to the left
after the restoration of the power.
Explanation:
Right
traverse
Left
traverse
The status of the latched devices (in this example FX M coils M600 and M601) is retained
during the power down. Once the power is restored the battery backed M coils latch
themselves in again, i.e. the load M600 is used to drive M600.
10.7
Indexing Through Multiple
Display Data Values
Many users unwarily fall in to the trap of only using a single seven segment display to display
only a single data value. This very simple combination of applied instructions shows how a
user can 'page' through multiple data values displaying each in turn.
Explanation:
T h e c o n t e n t s o f 1 0
counters are displayed in
a s e q u e n t i a l , ' p a g e d '
operation.
The paging action occurs
every time the input X11 is
received.
What actually happens is
that the index register Z is
continually incremented
until it equals 9. When this happens the comparison instruction drives M1 ON which in turn
resets the current value of Z to 0 (zero). Hence, a loop effect is created with Z varying between
fixed values of 0 and 9 (10 values). The Z value is used to select the next counter to be
displayed on the seven segment display.
This is because the Z index modifier is used to offset the counter being read by the BCD output
instruction.
Points Of Technique 10
FX
FX
FX
1S
1N
2N
FX
FX
FX
1S
1N
2N
10-5
FX
2NC
FX
2NC
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