53
10 Supplement
VEGACAL 62 • Profibus PA
30025-EN-160331
egram is structured.
Example 1
(standard setting) with distance value and additional cyclical value:
•
AI (PA-OUT)
•
Additional Cyclic Value
Byte-No.
1
2
3
4
5
6
7
8
9
10
Status
Status
Status
Status
(FB1)
IEEE-754-
Floating point value
PA-OUT
(FB1)
IEEE-754-
Floating point value
Additional Cyclic
Value
Format
Value
Example 2
with distance value without additional cyclical value:
•
AI (PA-OUT)
•
Free Place
Byte-No.
1
2
3
4
5
Status
Status
(FB1)
IEEE-754-
Floating point value
PA-OUT
(FB1)
Format
Value
Data format of the output signal
Byte4 Byte3 Byte2 Byte1 Byte0
Status
Value (IEEE-754)
Fig. 29: Data format of the output signal
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, 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. 30: Data format of the measured value
Coding of the status byte associated with the PA output value
Status
code
Description according to
Profibus standard
Possible cause
0x00
bad - non-specific
Flash-Update active
0x04
bad - configuration error
– Adjustment error
– Configuration error with PV-Scale (PV-Span too small)
– Unit irregularity
– Error in the linearization table
