9
DEVICE EXPLANATION
9
- 11
9.2 Internal User Devices
9.2.3 Internal relay (M)
9.2.3 Internal relay (M)
(1) Definition
Internal relays are auxiliary relays used in the CPU module.
All internal relays are switched OFF at the following times:
• When the PLC is powered OFF and then ON
• When the CPU module is reset
• When latch clear operation is executed.( Section 6.3)
(2) Latch execution of internal devices (backed up for power failure)
(a) For Basic model QCPU, High Performance model QCPU, Process CPU
The internal relays cannot be latched (backed up for power failure).
(b) For Redundant CPU
When the start mode is set to the hot start mode, the internal relays are latched
(backed up for power failure). When the start mode is set to the initial start mode,
the internal relays are not latched (backed up for power failure).
(3) Number of used N/O and N/C contacts
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 exceded.
(4) Procedure for external outputs
Outputs (Y) are used to output sequence program operation results to an external
destination.
POINT
Latch relays (L) should be used when a latch (memory backup) is
required.( Section 9.2.4)
Diagram 9.9 Use of internal relays in program
X0
M0
T0
Y20
X1
M0
M100
X2 M0
M2047
SET M0
K20
No restrictions on the quantity used.
M0 switches ON at X0 OFF to ON.
The internal relay (M0) ON can only be used for
internal CPU module processing, and cannot be
output externally.
M0 ON/OFF information is output from the output
module to an external destination.
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