Analog Value Representation Of Analog Input Modules - Siemens SIMATIC S5-100U System Manual

S5-100U
11.4

Analog Value Representation of Analog Input Modules

Each analog process signal has to be converted into a digital format, to be stored in the process
image input table (PII). The analog signals are converted into a binary digit that is written in one of
the following ways:
• In one byte (466-8MC11)
• In two bytes (the remaining analog input modules)
Each bit position has a fixed value in powers of two (see Tables 11-4 and 11-14). Analog values
are represented in two's complement.
The following tables show the analog value representations of the different analog inputs in 2-byte
format. You will need this information to program FB250 and FB251 (see section 11.6).
Table 11-4. Representation of an Analog Input Value as Bit Pattern
Bit Number
Analog Value Represent.
Key: S Sign bit
X Irrelevant bits
E Error bit
OV Overflow bit
Analog value representation for analog input modules 464-8...
Table 11-5. Analog Input Module 464-8MA11, -8MF11, -8MB11 (Bipolar Fixed-Point Number)
Measured Value
Units
in mV
>4095 100.0 1000.0
4095 99.976 999.75
2049 50.024 500.24
2048 50.0 500.0
1024 25.0 250.0
1 0.024
0 0.0
-1 - 0.024
-1024 - 25.0 - 250.0
-2048 -50.0 -500.0
-2049 -50.024 -500.24
-4095 -99.976 -999.75
<-4095 -100.0 -1000.0
464-8MA11/-8MA21 "No linearization"
464-8MF11 (2x±500 mV)
464-8MB11 (4x±1 V)
EWA 4NEB 812 6120-02b
High Byte
7 6 5 4 3
S 2 11 2 10 2 9 2 8
0="+", 1="-"
0= no wire break; 1=wire break
0= Measured value 4095 units at the most
1= Measured value greater than or equal to 4096 units
High Byte
2000.0 0 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1
1999.5 0 1 1
1000.48 0 1 0
1000.0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
500.0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
0.24 0.48 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
0.0 0.0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-0.24 -0.48 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0
- 500.0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0
-1000.0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
-1000.48 1 0 1 1 1 1 1 1 1 1 1 1 1 0 0 0
-1999.5 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
-2000.0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1
(4x±50 mV)
Analog Value Processing
2 1 0 7 6 5
2 7 2 6 2 5 2 4 2 3 2 2
Low Byte
1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 1
Low Byte
4 3 2 1 0
2 1 2 0 X E OV
Range
Overflow
0 0 0
Overrange
0 0 0
Nominal range
Overrange
Overflow
11-11