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CHAPTER6 FUNCTIONS
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6.3 Latch Function
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6.3 Latch Function
(1) Definition
This function holds data in each device of the CPU module when:
• the CPU module is powered off and then on,
• the CPU module is reset, or
• power failure occurs exceeding the allowable momentary power failure time.
Data in each device of the CPU module is cleared and set back to its default (bit device: off, word
device: 0) without using the latch function.
(2) Application
This function is used to hold the data managed by sequential control and continue control operation
especially when the CPU module is powered off and then on.
(3) Program operation when the latch function is use
Program operation is the same, regardless of the latch status.
(4) Devices that can be latched
The following devices can be latched.(By default, only the latch relay is enabled for latch.)
• Latch relay (L)
• Link relay (B)
• Annunciator (F)
• Edge relay (V)
•Timer (T)
• Retentive timer (ST)
• Counter (C)
• Data register (D)
• Link register (W)
When the battery life-prolonging function ( Section 6.26) is set, the latch relay cannot be
latched.