Siemens ET 200S - Page 376

Analog Electronic Modules
12-20
Distributed I/O System ET 200S
EWA 4NEB 780 6024-02 07
12.1.4 Analog Value Representation for Measuring Ranges with
SIMATIC S5
Analog Value Representation
The analog inputs have a resolution of 11 bits + sign (S) or 12 bits + sign (S),
whereas the analog outputs have a resolution of 11 bits + sign (S). Each analog
value is entered in the accumulator with left justification.
Analog values are represented in twos complement.
Analog Inputs
The following table shows the analog value representation of the analog electronic
modules with analog inputs. For the lower resolutions, the lower bits are filled
with “0”.
Table 12-25Analog Value Representation of the Analog Inputs (SIMATIC S5 Format)
Resolution
Analog Value
Bit number 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Significance of the bits S 2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
x E O
S 2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
x x E O
Sign
The sign (S, +/–) of the analog value is always in bit number 15:
 “0” ³ )
 “1” ³ *
Irrelevant Bits
Irrelevant bits are marked “x”.