FCI ST100A Series, Installation, Operation And Maintenance Manual

Page: 86 / 170

OPERATION ST100A Series Flow Meter
78 Fluid Components International LLC
Figure 58 – ST100A Series Configuration Software Modbus Tab, Serial Interface Configuration
ST100A Series Modbus Commands
With the Modbus protocol the instrument data is read and written via multiple register access. The following public function numbers are
defined for communication with the ST100A Series: 03, 04, and 06.
Table 20 – ST100A Series Modbus Function Codes
Function Code Description Register Group
03
Read Holding Registers:
•
Flow, Temperature, Totalizer, Pressure
•
Flow unit, Temperature unit, Totalizer unit, Pressure unit
•
Totalizer Enable/Disable Status register
4xxxx
04
Read Input Registers:
•
Flow, Temperature, Totalizer, Pressure
•
Flow unit, Temperature unit, Totalizer unit, Pressure unit
3xxxx
06
Write Single Register:
•
Reset Totalizer counter
•
Enable Totalizer
•
Disable Totalizer
4xxxx
See Table 23 (page 82 ), Table 24 (page 83 ), and Table 25 (page 83 ) for Modbus engineering unit codes, exception codes, and register
information, respectively.
ST100A Series Process Data Registers
Two data type registers are set up in the ST100A Series to access the process data. One uses integer data registers (4000) and the other
uses the Daniel extension data registers (5000).
All designated registers must be read for each variable value to extract the floating-point number. Conversion must be started manually
with the 4000 registers. The Daniel extension handles the read and conversion automatically. To use the Daniel extension the master must
support the Daniel extension function.
Totalizer Description
The ST100A Series through the Modbus channel offers the flow Totalizer value through three different register groups organized into two
forms of floating point data types. Registers 5103 and 5104, offer the flow Totalizer as a double precision floating point value in the
Modbus Daniel extension protocol. Registers 4105, 4106, 4107, and 4108 offer the flow Totalizer as a double precision floating point value