Siemens NAN 67 Series Wartungshandbuch PDF herunterladen (Seite 248)

20-14

Ladder Logic (LAD) for S7-300 and S7-400

C79000-G7076-C504-02

When the MCRA instruction activates the MCR function, you can create up to eight nested MCR

zones. In the example, there are two MCR zones. The first MCR> instruction works together with the

second MCR< instruction. All instructions between the second set of MCR brackets (MCR<MCR>)

belong to the second MCR zone. The operations are executed as follows:

S If the signal state of input I 0.0 = 1, the signal state of input I 0.4 is assigned to output Q 4.1.

S If the signal state of input I 0.0 = 0, the signal state of output Q 4.1 is 0 regardless of

the signal state of input I 0.4. Output Q 4.0 remains unchanged regardless of the signal state

of input I 0.3.

S If the signal state of input I 0.0 and I 0.1 = 1, output Q 4.0 is set to 1 if the signal state

of input I 0.3 is 1 and output Q 4.1 = input I 0.4.

S If the signal state of input I 0.1 = 0, output Q 4.0 remains unchanged regardless of

the signal state of input I 0.3 and input I 0.0.

I 0.0

I 0.1

I 0.3

Q 4.0

Status Word Bits

BR CC 1 CC 0 OV OS OR STA RLO FC

Write – – – – – 0 1 – 0

I 0.4

MCR>

MCRD

MCR <

MCRA

MCR>

Q 4.1

MCR <

Figure 20-8 Master Control Relay Off

Program Control Instructions

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Siemens NAN 67 Series Wartungshandbuch Seite 248