VEGA VEGACOM 557 Modbus protocol - Manual (Page 40)

40 VEGACOM 557 Modbus
Parameter adjustment of VEGALOG or VEGAMET in RTU mode
VEGACOM 557 also provides the option of enquiring and modifying different parameters of
the VEGALOG or VEGAMET signal conditioning instruments (relating to measurement loop).
The following list gives an overview of the affected parameters:
Parameter name possible access mode
Density reading writing
Relay switching point (top) reading writing
Relay switching point (bottom) reading writing
Integration time reading writing
Scaling (0 %) reading writing
Scaling (100 %) reading writing
Current offset reading writing
Activate offset adjustment – writing
Independent of the connected VEGA signal conditioning instrument (VEGAMET or VEGA-
LOG), the enquiry or modification of parameters is made via the Profibus always according to
the same procedure via the function codes 16 (= Preset Multiple Registers) and 04 (Read
Input Registers).
With the command "Preset Multiple Registers“ the data for the parameter enquiry are trans-
ferred to VEGACOM 557. For reading access, 3 register words are necessary and for writing
access 4 register words.
After VEGACOM 557 has confirmed the transfer, a cyclical enquiry must be made with a sec-
ond command "Read Input Registers“ (function code 04), to get the information that the
processing is finished. VEGACOM 557 signals an Exception Code "Slave Device Busy“,
(0x06) until either the data has been processed or the processing time has elapsed. As start
address are valid, e.g. 30500, 31500 or 32500, etc. for the Modicon or 499, 1499 or 2499, etc.
when accessing via your own self-written communication driver.
For further information, please contact one of our employees.
Data transmission with Modbus RTU