Siemens SIMATIC S7-300 Module data - 5 Representation of the Analog Values of Analog Modules

S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
5-1
Representation of the analog values of analog
modules
5
Introduction
This chapter describes the analog values for all measuring or output ranges supported by
the analog modules.
Analog to digital conversion
The CPU only processes the analog values in binary format.
Analog input modules convert the analog process signal to a digital format.
Analog output modules convert digital output values to analog signals.
Representation of analog values at a resolution of 16 bits
The digitized analog value applies to input and output values of the same nominal range.
Analog values are output as real numbers in two's complement. The resultant assignment:
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Bit values 2
15
2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
Sign
The sign of the analog value is always set at bit 15:
● "0" → +
● "1" → -
Resolution < 16 bits
On analog modules with a resolution of < 16 bits, the analog value is stored left-aligned. The
unused least significant bit positions are padded with zeros ("0".)