User guide

VEGACOM 557 Profibus DP 25
5 Transfer of measured value
As DP norm slave, the VEGACOM 557 DP
gateway is either configured with 50 Byte
consistent input data and 2 Byte consistent
output data or with 6 Byte consistent input
data and 6 Byte consistent output data (see
chapter „6 Operating mode VEGACOM
557“)
. The DP master transmits via the inputs
control information to VEGACOM 557, to
which VEGACOM 557 r esponds accor dingly,
making the data available to the DP master
as input information.
5.1 Format for transfer of measured
value
Measured values and PC/DCS values
The measured values of the VEGA process-
ing systems (VEGAMET or VEGALOG) con-
nected to VEGACOM 557 are reproduced on
the input bytes of the Profibus master as
described in chapter 4. They are available in
VEGACOM 557 as so-called PC/DCS values.
A PC/DCS value consists of 6 Byte.
Structure of a measured value
Measured values of VEGALOG or VEGAMET
processing system are transferred to VEGA-
COM 557 as 2 Byte signed data. This means
that the value range comprises max.
+32.768 up to -32.767.
Structure of a PC/DCS value
An individual PC/DCS value in VEGACOM
557 consists of 6 Byte and is structured as
follows:
PC/DCS value
Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6
Additional info. High word Low word
Measured value
Index Status
high
low high low
Transfer of measur ed value
The real measured value is in the low word of
the measured value and with a length of 2
Byte and signed, this means that the value
range is +32768 up to -32767.
The 2 Byte of the high word of the measured
value are not used at present - they are filled
with the value zero.
In addition to the measured value, VEGA-
COM 557 provides per DCS value one Byte
for the PC/DCS index and another Byte for
information on the current measured value
status.
The PC/DCS output number is transferred in
the byte index. The status describes the
conditions of the respective measured value.
The contents of the measured value is only
valid if the respective status has the value
zero.
If the status value is not equal to zero, the
status value and the respective value in the
measured value field must be taken into
account for a detailed error diagnosis. The
following list explains the possible errors:
Status M eas. valueMeaning
0x00 0xXXXX valid measured value
0x01 0xXXXX simulated meas. value
(only on VEGAMET 509
and 512)
0x80 0xXXXX old meas. value (prob-
ably connection sepa-
rated)
0xFE 0x0000 there is no meas. value
available (not config-
ured)
0xFF 0xFFFF there is no VEGAMET or
VEGALOG connected
0xFF 0x00XX failure message of an
individual meas. loop
XX = error type
0xFF 0x8000 failure message of an
individual meas. loop
Error type not defined