Siemens SITRANS LG250 Operating Instructions Manual page 82

Examples of telegram configuration
In the following you will see how the modules can be combined and how the appendant data tel-
egram is structured.
Example 1
•
AI FB1 (OUT)
•
AI FB2 (OUT)
•
AI FB3 (OUT)
Byte- 1 2
No.
Format IEEE-754-Floating point
value
Value AI FB1 (OUT)
Example 2
•
AI FB1 (OUT)
•
Free Place
•
Free Place
Byte-No.
Format
Value
Note:
Data format of the output signal
Byte2 Byte1 Byte0
Byte4 Byte3
Status Value (IEEE-754)
Fig. 39: Data format of the output signal
The status byte corresponds to profile 3.02 "Profibus PA Profile for Process Control Devices" coded.
The status "Measured value OK" is coded as 80 (hex) (Bit7 = 1, Bit6 ... 0 = 0).
The measured value is transferred as a 32 bit floating point number in the IEEE-754 format.
Byte n
Bit Bit Bit Bit Bit Bit Bit
4
7 6 5 3 2 1
2
VZ 2 7 2 6 5 2 4 2 3 2
Sign
Exponent
Bit
(Exponent - 127)
Value = (-1) VZ 2
Fig. 40: Data format of the measured value
82
3 4 5 6
Status IEEE-754-Floating point
AI FB1
1 2
IEEE-754-Floating point value
Bytes 6-15 are not used in this example.
Byte n+1
Bit Bit Bit
Bit Bit Bit Bit
0
7 6 5 4 3 2
2
2 0 2 2 -2 2 -3 2 -4 2
2 1 -1
Significant
(1 + Significant)
SITRANS LG250 - Operating Instructions
7 8 9
Status
value
AI FB2 (OUT) AI FB2
3
AI FB1 (OUT)
Byte n+2
Bit Bit Bit Bit Bit
Bit
Bit
7 6 5 4
1 0
2 2 -9 2 -10 -11 -12 -13 -14 -15 -16 -17 2
2 -6 2 -7 -8
-5
Significant
10 11 12 13
IEEE-754-Floating point
value
AI FB3 (OUT)
4
Status
AI FB1
Byte n+3
Bit Bit Bit
Bit Bit Bit
3 2 1 0 7
6 5
2 2 2 2 2 2 2 -18 -19 -20 -21 -22 -23
14 15
Status
AI FB3
5
Bit
Bit Bit Bit
Bit
4
3 2 1 0
2 2 2 2
2
Significant
PBD-51041053