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Siemens S5-135U/155U User Manual

Page 323

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8-11

System Manual
C79000-G8576-C199-06

Only the flag word (FW) may be accessed during the cyclic program.

Accessing the I/O bytes in the process image will result in alarm loss.
Addressing of the module must therefore be above address 127. Double
accessing of I/O bytes, even from different CPUs, is not permissible (alarm
loss).

The four I/O bytes of a module must be scanned successively and in
ascending order. The scanning of byte n inhibits the input circuit of the
module, and the scanning of byte (n + 3) enables them again.

Make the following settings on the module to operate it with a process alarm
via IB 0:

Step

Action

1

Insert jumpers X3 and X4

2

Set switch row S1 to Off.

3

Set bit 0 on switch row S2 to On, and all other switches to Off.

4

Set switch row S3 to choose whether the interrupt is to be initi-
ated with a positive-going (leading) or negative-going (trail-
ing) edge. The setting of a pair of switches applies to an entire
byte.

S1

3

3

3

Bit 3

IR-D

4

4

4

Bit 4

IR-E

5

5

5

Bit 5

IR-F

6

6

6

Bit 6

IR-G

7

7

7

Bit 7

INT

0

0

0

Bit 0

IR-A

1

1

1

Bit 1

IR-B

2

2

2

Bit 2

IR-C

S2

S3

Byte 0

Byte 1

Byte 2

Byte 3

}

}

}

}

:OFF

:ON

Byte 0: Positive-Going Edge
Byte 1: Negative-Going Edge-
Byte 2: Both Edges
Byte 3: No Process Interrupt

Figure 8-5

Switch Settings for Operation with Process Alarm via IB 0 (Example)

Settings on the
Module

Digital Input/Output Modules