Special Relays, Special Registers - Mitsubishi Electric FR - F700 Programming Manual

Special relays, special registers

3.12 Special relays, special registers
Special relays and special registers are internal relays and data registers, respectively,
whose applications are predetermined by the built-in PLC functions.
They have the following main applications.
(1) Sequence operation check
The special relays and special registers can be used to:
(a)Check the operating status (RUN/STOP)
(b)Detect a fault by the self-diagnostic function
(c)Detect an operation error
(d)Check the scan time
(2) Timing contact
There are special relays that can be used in a sequence program and differ in
operating status.
(a)Normally ON/OFF flag
(b)RUN flag (OFF for 1 scan)
(c)Initial processing flag (ON for 1 scan)
REMARKS
For the special relays and special registers usable with the built-in PLC function,
refer to page 13 .
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