Siemens SITRANS F M TRANSMAG 2, Руководство по эксплуатации, Страница: 96 / 114

Profibus Communication
B.4 Input Data (from Slave to Master)
SITRANS F M TRANSMAG 2
94
Operating Instructions, 11/2009, A5E00102775-07
B.4 Input Data (from Slave to Master)
The input data are useful data (measured values) transferred from the device to the master
in the following format with the "Data_Exchange" service: Every measured value consists of
5 bytes which are made up of a floating point value according to IEEE-754 (4 bytes) for the
measured value itself and the corresponding measured value status (1 byte). In the
PROFIBUS telegram, the measured value is transmitted first and then the corresponding
status.
Table B- 1 Measured value format
Byte Bit
No. 7 (MSB) 6 5 4 3 2 1 0 (LSB)
1 VZ E
2
7
E
2
6
E
2
5
E
2
4
E
2
3
E
2
2
E
2
1
2 E
2
0
M
2
-1
M
2
-2
M
2
-3
M
2
-4
M
2
-5
M
2
-6
M
2
-7
3 M
2
-8
M
2
-9
M
2
-10
M
2
-11
M
2
-12
M
2
-13
M
2
-14
M
2
-15
4 M
2
-9
M
2
-9
M
2
-9
M
2
-9
M
2
-9
M
2
-9
M
2
-9
M
2
-9
VZ: sign: 0 positive, 1 negative E: Exponent M: Mantissa
Status bytes
The status bytes consist of three components:
● Quality (the MSBs 6 and 7):
describes the basic quality of the corresponding measured value
● Substatus (bits 2 to 5):
Differentiates the quality of the corresponding measured value
● Limits (the LSBs 0 and 1):
indicate exceeding of the limit value
Table B- 2 Status byte format
Byte Bit
No. 7 (MSB) 6 5 4 3 2 1 0 (LSB)
5 Quality Substatus Limits
These components may adopt the following values in SITRANS F M: