VEGA VEGABAR 86 Profibus PA - Operating Instructions - Manual (Page 65)

65
11 Supplement
VEGABAR 86 • Profibus PA
45042-EN-131107
Example 1
•
AI FB1 (OUT)
•
AI FB2 (OUT)
•
AI FB3 (OUT)
Byte-
No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Format IEEE-754-Floating point
value
Status IEEE-754-Floating point
value
Status IEEE-754-Floating point
value
Status
Value AI FB1 (OUT) AI FB1 AI FB2 (OUT) AI FB2 AI FB3 (OUT) AI FB3
Example 2
•
AI FB1 (OUT)
•
Free Place
•
Free Place
Byte-No. 1 2 3 4 5
Format IEEE-754-Floating point value Status
Value AI FB1 (OUT) AI FB1
Note:
Bytes 6-15 are not used in this example.
Data format of the output signal
Byte4 Byte3 Byte2 Byte1 Byte0
Status Value (IEEE-754)
Fig. 33: 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 Byte n+1
Bit
7
VZ
Exponent
Bit
6
2
Bit
5
2
Bit
4
2
Bit
3
2
Bit
2
2
Bit
1
2
Bit
0
2
Bit
7
2
Bit
6
2
Bit
5
2
Bit
4
2
Bit
3
2
Bit
2
2
Bit
1
2
Bit
0
2
Sign
Bit
Significant
7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7
Byte n+2 Byte n+3
Bit
7
2
Significant
Bit
6
2
Bit
5
2
Bit
4
2
Bit
3
2
Bit
2
2
Bit
1
2
Bit
0
2
Bit
7
2
Bit
6
2
Bit
5
2
Bit
4
2
Bit
3
2
Bit
2
2
Bit
1
2
Bit
0
2
Significant
-9 -10 -11 -12 -13 -14 -15 -16 -17 -18 -19 -20 -21 -22 -23 -8
Value = (-1) VZ 2 (Exponent - 127) (1 + Significant)
Fig. 34: Data format of the measured value
Coding of the status byte associated with the PA output value
You can find further information for the coding of the status byte in the Device Description 3.02 on
www.profibus.com.