Cyclic Data Exchange - Endress+Hauser PROline prosonic flow 93 Operating Instructions Manual
Profibus-dp/-pa ultrasonic flow measuring system
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- Function manual (226 pages) ,
- Operating instructions manual (168 pages) ,
- Brief operating instructions (40 pages)
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PROline Prosonic Flow 93 PROFIBUS-DP/-PA
!
Endress+Hauser
6.4.1
Cyclic data exchange
Structure of a cyclic data telegram
In the case of PROFIBUS-DP/-PA, the cyclic transmission of analogue values to the
automation system is effected in data blocks 5 bytes in length. The measured value is
portrayed in the first 4 bytes in the form of floating point numbers in accordance with
IEEE 754 standard (see IEEE floating point number). The 5th byte contains status
information pertaining to the measured value which is implemented in accordance with
the Profile 3.0 Specifications (see Page 96). The status is indicated on the device
display (if present), (see Page 58).
Note!
An exact description of the data types can be found in the slot/index lists in the
"Description of Device Functions" manual.
IEEE floating point number
Conversion of a hexadecimal value into an IEEE floating point number for measured
value detection.
The measured values are shown in numerical format IEEE-754 in the following manner
and are transferred to the Class 1 master:
Byte n
Bit 7
Bit 6
Bit 0
7
6
5
4
3
2
1
Sign
2
2
2
2
2
2
2
Exponents
sign
Formula value = (-1)
Example: 40 F0 00 00 hex= 0100 0000 1111 0000 0000 0000 0000 0000 binary
0
(129-127)
Value = (-1)
* 2
* (1 + 2
2
= 1 * 2
* (1 + 0.5 + 0.25 + 0.125)
= 1 * 4 * 1.875 = 7.5
Block model
The process variables and control blocks transmitted by Prosonic Flow 93 during cyclic
data exchange are as follows:
Process variables
– Volume flow channel 1
– Sound velocity channel 1
– Flow velocity channel 1
– Volume flow channel 2
– Sound velocity channel 2
– Flow velocity channel 2
– Average volume flow
– Average sound velocity
– Total volume flow
– Volume flow difference
– Average flow velocity
– Totalizer 1–3 incl. controls
– Display value
– Control block for manufacturer-specific functions
Byte n+1
Bit 7
Bit 6
Bit 0
0
-1
-2
-3
-4
-5
-6
-7
2
2
2
2
2
2
2
2
Mantissa
(exponent -127)
* 2
* (1 + mantissa)
-1
-2
-3
+ 2
+ 2
)
Assignment to the AI Blocks
Process variables which can be
assigned as required to the Analog
Input function blocks AI 1...AI 8.
Cannot be assigned to the Analog
Input function blocks AI 1...AI 8.
6 Commissioning
Byte n+2
Bit 7
Bit
0
-8
-9
-10
-11
-12
-13
-14
-15
2
2
2
2
2
2
2
2
Mantissa
Byte n+3
Bit 7 Bit 0
-16
-23
2
...2
Mantissa
99
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