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S5-115U Manual
10.6
Representation of the Digital Input Value
The analog value has the same representation in the three analog input modules.
However, there are differences in the case of analog value evaluation where the individual
analog input modules are concerned, especially bits 0 to 2 (see Figure 10-24).
After an analog signal is converted, the digital result is stored in the module's RAM. Figure 10-24
explains the individual bits of the two bytes.
Byte
Bit
Fault bit; is set in the event of an internal fault; the
Figure 10-24. Representation of the Digitized Measured Value
Bits 0 to 2 are irrelevant for the measured value. They provide information on the measured value
representation. Table 10-17 describes these bits in detail.
Table 10-17. Meaning of Bits 0 to 2 for Analog Input Modules
Bit
Meaning
OV
Overflow bit
F
Fault bit
A
Activity bit
*
An overflow at one measuring point has no effect on the overflow bits of the other channels, i.e. the values on the
other channels are correct and may be evaluated.
EWA 4NEB 811 6130-02b
High-Order-Byte
n
15 14 13 12 11 10
2
2
2
2
2
2
12
11
10
9
8
7
Binary measured value
Activity bit; not used on the AI 466-3LAA
measured value read in is then not valid
Overflow bit; is set when the
measuring range limit is reached
Signal
State
1
1
0
1
Analog Value Processing
Low-Order-Byte
n+1
9
8
7
6
5
4
2
2
2
2
2
2
6
5
4
3
2
1
Meaning of the Signal State
Range exceeded
Wire break
Cyclic scan or "Not active"
(for single scan)
Coding procedure for single scan not yet
terminated
3
2
1
0
2
T
F
Ü
0
*
10-39
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