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MELSEC-Q
10 DEVICES
10.2.4 Latch relays (L)
(1) Definition
(a) Latch relays are auxiliary relays which can be latched by the programmable
controller's internal latch (memory backup).
Latch relay operation results (ON/OFF information) are saved even in the
following cases:
• When power is switched from OFF to ON.
• When reset occurs.
The latch is backed up by the High Performance model QCPU battery.
(b) Latch relays can be switched OFF by pertorming latch clear for the High
Performance model QCPU. However, the latch relay set as "Latch (2):
Cannot clear with Latch Clear key" at the "Device" tab screen in the “(PLC)
Parameter" dialog box cannot be turned off, even when the RESET/L.CLR
switch/remote latch clear is made for latch clear of it.
(c) There are no restrictions on the number of contacts (N/O contacts, N/C
contacts) used in the program, provided the program capacity is not
exceeded.
X0
L0
T0
Y20
X1
L0
L100
X2
L0
L2047
SET
L0
K20
No restrictions on the quantity used.
L0 switches ON at X0 OFF to ON.
The latch relay (L0) ON can only be used for internal
QCPU processing, and cannot be output externally.
L0 ON/OFF information is output from the output
module to an external destination.
Figure 10.6 Latch Relay
(2) Procedure for external outputs
Outputs (Y) are used to output sequence program operation results to an
external destination.
REMARK
Internal relays (M) should be used when a latch (memory backup) is not required.
See Section 10.2.3 for details on internal relays.
Содержание QCPU (Q Mode)
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