Latch Function - Mitsubishi Electric L02SCPU User's Manual And Reference

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 latched.)
• Latch relay (L)
• Edge relay (V)
• Counter (C)
The following devices also can be set when a file register is set to be used in the PLC file.
• File register (ZR)
When the battery life-prolonging function is set, the latch function is disabled. ( Page 198, Section 3.33)
(2) Latch range setting
Set the following.
Project Window  [Parameter]  [PLC Parameter]  [Device]
• Latch clear operation enable range (Latch (1) Start/End): Data in this range can be cleared by a latch clear
operation.
• Latch clear operation disable range (Latch (2) Start/End): Data in this range cannot be cleared by a latch
clear operation.
Set latch ranges by the start and
end device numbers.
88
• Link relay (B)
• Timer (T)
• Data register (D)
• Extended data register (D)
• Annunciator (F)
• Retentive timer (ST)
• Link register (W)
• Extended link register (W)