VEGA VEGASCAN 850 Modbus signal output - Manual (Page 6)

6 Modbus signal output VEGASCAN 850
High-Byte Low-Byte Unit Status
Measured value Add. info
DCS value
Octet 1 Octet 2 Octet 3 Octet 4
4 Format for transfer of measured
values
Measured values and DCS values
The measured values of VEGASCAN 850 are
imaged according to the way described in
chapter "1.2 Data image in VEGASCAN 850“
to the input registers of the Modicon 584.
They are available in VEGASCAN for collec-
tion as so-called DCS values.
A DCS value reserves two register ad-
dresses, it consists of 2 double words, i.e. 4
bytes.
A complete overview on the image of the
DCS values in the input register of Modicon
or alternative addressings can be found in
chapter "1.6 Measured value image“.
Structure of a measured value
Measured values of VEGASCAN consist of 2
octets reserving signed data. This means
that the value range comprises max. +32768
to -32767.
Structure of a DCS value
A single DCS value in VEGASCAN consists
of 4 octets and is composed as follows:
The real measured value has a length of 2
octets and is signed, this means that the
value range is between +32768 and -32767.
In addition to the measured value,
VEGASCAN provides one octet per DCS
value for information on the unit of measure-
ment and an additional octet for information
on the actual status of the measured value.
The octet for the unit of measurement is not
presently used, it is always filled with the
value zero.
The status describes the mode of the re-
spective two measured value octets. The
content of the measured value octet 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 0x0000 no measured value
available (not config-
ured)
0xFF 0xFFFF no VEGASCAN con-
nected
0xFF 0x00XX Error information of a
single measurement
loop
XX = kind of error
0xFF 0x8000 Error information of a
single measurement
loop
Kind of error is not
defined
Format for transfer of measured values