1.
5. INTERNAL RELAYS
Internal relays are built-in functions with PLC. They have other terms widely
used: auxiliary relays, markers, bit storage and coils. Their addresses are ranging
from M0.0 to M255.7
Internal Bit Storage (Markers)
Internal relay Resetting Latch
Motor start/stop using only ONE push button (Task3)

2.
Latching using Set and Reset Coil, S-R and R-S Flip Flop
(Task1)
Set – Reset with Reset priority (Task4)
Set – Reset with Set priority

3.
Master Control Relay
MCR functionality is activated by the MCRA rung.
The rungs between the MCR< and the MCR> (outputs Q4.0, Q4.1) are executed
as follows:
- I0.0 = "1" ( MCR is ON ): Q4.0 is set to "1" if I0.3 is logic "1", or will
remain unchanged if I0.3 is "0" and the logic state of I0.4 is assigned to
Q4.1.
- I0.0 = "0" ( MCR is OFF): Q4.0 remains unchanged regardless of the logic
state of I0.3 and Q4.1 is "0" regardless of the logic state of I0.4.
- In the next rung, the instruction ---(MCRD) deactivates the MCR. This
means that you cannot program any more MCR zones using the
instruction pair ---(MCR<) and ---(MCR>).

4.
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