3 data format of the output signal – VEGA VEGAPULS 56 Profibus PA User Manual
Page 85
VEGAPULS 56 Profibus PA
85
Technical data
8.3 Data format of the output signal
Byte4
Byte3
Byte2
Byte1
Byte0
Status
Measured value (IEEE-754 Format, see below)
Status byte:
The status byte corresponds to profile 3,0 "Profibus PA Profile for Process Control Devices“
coded. The status "Measured value OK“ is coded as 80 (hex) (Bit7 = 1, Bit 6 … 0 = 0).
Measured value:
The measured value is transmitted as 32 Bit floating point figure in IEEE-754 format.
Byte n
Byte n+1
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
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
Sign
Exponent
Mantissa
Byte n+2
Byte n+3
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
Bit
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
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
Formula:
Measured value = (-1)
VZ
• 2
(Exponent - 127)
• (1 + Mantissa)
Examples:
41 70 00 00 (hex) = 0100 0001 0111 0000 0000 0000 0000 0000 (bin)
Meas. value
= (-1)
0
• 2
(130 - 127)
• (1 + 2
-1
+ 2
-2
+ 2
-3
)
= 1 • 2
3
• (1 + 0.5 + 0.25 + 0.125)
= 1 • 8 • 1.875
= 15.0