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S5-90U/S5-95U
Nota
If you used analog inputs as digital inputs and then use the digital inputs as analog
inputs again, accuracy can no longer be guaranteed.
12.2
Output of Analog Values
The bit pattern output by the PLC is converted into analog output voltages or currents at the
outputs.
The following Table shows the various possibilities for the output of analog values via onboard I/Os
and external I/Os.
Table 12-11. Possibilities for the Output of Analog Values
Possibilities for the Output of
Analog Values
Writing analog values into the
process image
Writing analog values to the
outputs via direct I/O access
12.2.1 General Representation of Analog Output Values
The analog output values are written into two bytes as can be seen in the following Table.
Table 12-12. General Representation of the Analog Output Value as Bit Pattern
Bit number
Analog value represent.
Legend:
X
Irrelevant bits
Representation of Analog Value Output via Onboard I/Os
The voltages and currents output depending on the units (in QW 40) are listed in Table 12-13. If the
value in QW 40 exceeds 1024 units, 10 V (or 20 mA) are automatically output. If the sign bit (bit 7 in
the high-order byte) is set (negative value), 0 V (0 mA) will be automatically output.
EWA 4NEB 812 6115-02b
Onboard I/Os
•
Using the T QW 40
operation or
•
Using FB251
•
Using the T PW 40
operation
High-Order Byte
7
6
5
4
3
2
10
9
8
7
6
S
2
2
2
2
2
Analog Value Processing
External I/Os
(Analog Output Module)
•
Using the T QW ... operation
or
•
Using FB251
Not possible
Low-Order Byte
1
0
7
6
5
4
5
4
3
2
1
0
2
2
2
2
2
2
3
2
1
0
X
X
X
X
12-9
- Quick Links:
- All Inputs and Outputs
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