VEGA VEGASCAN 850 Profibus DP signal output - Manual (Page 7)

Profibus DP signal output VEGASCAN 850 7
Transfer of measured value
3 Transfer of measured value
The VEGASCAN DP-Gateway is configured
as DP-Normslave either with 50 byte consist-
ent input data and 2 byte consistent output
data with 6 byte consistent input data and 6
byte consistent output data. The DP master
transmits control information via the outputs
to VEGASCAN, to which VEGASCAN an-
swers respectively, outputting the data as
input information to the DP master.
3.1 Format for transfer of measured
value
Measured values and PC/DCS values
The measured values of the measurement
loops created on VEGASCAN are imaged
according to the way described in chapter
"2 PC/DCS output in VEGASCAN“ to the input
bytes of the Profibus master. They are avail-
able in VEGASCAN as so-called PC/DCS
values for collection.
A PC/DCS value consists of 6 bytes.
Structure of a measured value
Measured values of VEGASCAN consist of 2
bytes signed data. This means that the value
range comprises max. +32768 to -32767.
Structure of a PC/DCS value
A single PC/DCS value in VEGASCAN con-
sists of 6 bytes and is composed as follows.
PC/DCS value
Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6
Add. info High-Word Low-Word
Measured value
Index Status high low high low
The real measured value is in the low word of
the measured value and has a length of 2
bytes and is signed, this means that the
value range is +32768 to -32767.
The 2 bytes of the high word of the measured
value are actually not used, they are filled
with the value zero.
In addition to the PC/measured value,
VEGASCAN provides one byte per DCS
value for the PC/DCS index and another byte
for information on the actual status of the
measured value.
The PC/DCS output number is transmitted in
the byte index. The status describes the
condition of the respective measured value.
The content of the measured value is only
valid if the respective status has the value
zero.
If a status value unequal zero is returned, the
status value and the respective value in the
measured value field must be taken into
consideration for a detailed error diagnosis.
The following list explains possible errors:
Status Meas. value Meaning
0x00 0xXXXX valid measured value
0x80 0xXXXX old meas. value (pro-
bably connection inter-
rupted)
0xFE 0x0000 no measured value
available (not config-
ured)
0xFF 0xFFFF no VEGASCAN con-
nected
0xFF 0x00XX Error information of a
single measurement
loop
XX = Error type
0xFF 0x8000 Error information of a
single measurement
loop
Error type is not defined