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6.3 Latch Function
6
FUNCTIONS
(7) Clearing the Latch Range Device Data
The status of devices to which "latch clear" is made is shown in Table6.3.
* : Refer to Section 3.7 for the clearing method.
POINT
File registers (R, ZR) cannot be cleared with latch clear.
Clear the file registers (R, ZR) by performing data clear operation using a
sequence program or GX Developer. (
(8) Precautions
(a) When local device or device initial value is specified
Even if the device has been latch-specified, it will not be latched the when the
local device
or the device initialization is specified.
Note4Note5
(b) Use of battery
The device details of the latch range are maintained with the battery attached to
the CPU module.
• If boot run is executed by the CPU module, the battery is required for latch.
• Take care that, if the battery connector is disconnected from the connector of
the CPU module when PLC is turned off, the latch range device memory is
not retained but becomes undefined.
(c) When start mode of Redundant CPU is hot-start mode
When the start mode is the hot-start mode, the data not set to be within the latch
range are also held. (Except some devices such as the index register and step
relay)
To clear these data, perform latch clear operation (
Section 3.7(2)(b)).
Table6.3 Status when lath clear is performed
Latch setting
Clear/retention after "latch clear"
Devices not specified to be within latch range
Clear
Latch (1) setting (Devices with "latch clear" option)
Clear
Latch (2) setting (Devices without "latch clear"
option)
Retain*
Note4
Note5
Basic
Note6.5
The Basic model QCPU does not support local device designation.
Basic
