Technical Specifications
7-94
ET 200X Distributed I/O Device
EWA 4NEB 780601602-06
7.21.4 Analog value representation for measuring ranges with
SIMATIC S5
Analog value representation
The analog inputs have a resolution of 12 bits + plus/minus sign, whereas the
analog outputs have a resolution of 11 bits + plus/minus sign. Each analog value is
entered in the accumulator with left justification.
The analog values are represented in the form of a twos complement.
Analog inputs
The following table shows the analog value representation of the expansion
modules with analog inputs:
Table 7-50 Analog 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 +/
–
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 F Ü
Sign
The sign (+/–) of the analog value is always in bit number 15:
”0”
”1”
Irrelevant bits
Irrelevant bits are marked ”x”.
Diagnostic bits
Bit numbers 0 and 1 are reserved for diagnostic functions, whereas bit number 2
does not have a function.
E = error bit (0 = no wire break; 1 = wire break)
O = overflow bit
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