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CHAPTER 3 CPU MODULE FUNCTIONS
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3.4 Latch Function
3.4 Latch Function
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
• a power failure occurred exceeding the allowable momentary power failure time.
Data in each device of the CPU module are cleared and set back to its default (bit device: off, word device: 0) when
this function is not used. By using this function, the operation can be continued with the previous data even after
powering off the CPU module while the data are managed by a sequential control. Program operation does not change
regardless of the latch
(1) Devices that can be latched
Set the device to latch among the following. (By default, only the latch relay is allowed to be latched.)
When the battery life-prolonging function is set, the latch function is disabled. ( Page 166, Section 3.30)
(2) Latch range setting
Set the following.
Project Window [Parameter] [PLC Parameter] [Device]
• Latch clear is enabled (Latch (1) Start/End): The latch range that can be cleared by remote latch clear
operation
• Latch clear is disabled (Latch (2) Start/End): The latch range that cannot be cleared by remote latch clear
operation
• Latch relay (L) • Link relay (B) • Annunciator (F)
• Edge relay (V) • Timer (T) • Retentive timer (ST)
• Counter (C) • Data register (D) • Link register (W)
• File register (ZR) • Extended data register (D) • Extended link register (W)
Set latch ranges by the start and
end device numbers.
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