Application profile, 1 function blocks, 2 data structure of function block output values – KROHNE MFC 300 Profibus User Manual
Page 25: 1 float value
APPLICATION PROFILE
4
25
MFC 300
www.krohne.com
07/2014 - 4001086802 - AD MFC 300 PROFIBUS R02 en
4.1 Function blocks
The PROFIBUS MBP interface is based on the PROFIBUS PA Profile Version 3.0 and supports the
following blocks:
• 1 physical block.
This block contains the parameters defined in PA Profile 3.0.
• 1 transducer block for Coriolis mass flow devices.
This block provides the parameters and functions defined in PA Profile 3.0.
• 8 Analog Input (AI) function blocks.
As default: Mass Flow / Density / Medium Temperature / Volume Flow / Concentration 1 /
Concentration 2 / Concentration Mass Flow 1 / Concentration Mass Flow 2 /.
• 3 totalizer (TOT) function blocks.
As default the first and the third totalizers will totalize "Mass" and the second one will totalize
"Volume".
4.2 Data structure of function block output values
The data structure of function block outputs consists of 5 bytes: a 4 byte float value (Float Format
according IEEE Standard 754 Short Real Number) followed by a 1 byte status value. If all 11
function block outputs have been configured (see above), 55 bytes will be transmitted.
4.2.1 Float value
Example of float format
Example (binary): 40 F0 00 00 (hex) = 0100 0000 1111 0000 0000 0000 0000 0000
Formula:
Formula:
Formula:
Formula:
value = (-1)
VZ
* 2
(Exponent – 127)
* (1 + Mantissa)
value = (-1)
0
* 2
(129 – 127)
* (1 + 2
-1
+ 2
-2
+ 2
-3
)
value = 1 * 4 * (1 + 0.5 + 0.25 + 0.125)
value = 7.5
Byte n
Byte n+1
Bit7
Bit6
Bit7
Bit6
VZ
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
2
-1
2
-2
2
-3
2
-4
2
-5
2
-6
2
-7
Exponent
Mantissa
Byte n+2
Byte n+3
Bit7
Bit7
2
-8
2
-9
2
-10
2
-11
2
-12
2
-13
2
-14
2
-15
2
-16
2
-17
2
-18
2
-19
2
-20
2
-21
2
-22
2
-23
Mantissa
Mantissa