Fluid Components Intl ST51A - ST51 A;ST75 A;ST75 AV Modbus Commands; ST51 A;ST75 A;ST75 AV Process Data Registers; Table 19 - ST51 A;ST75 A;ST75 AV Modbus Function Codes

ST51A/ST75A/ST75AV Mass Flow Meters OPERATION
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ST51A/ST75A/ST75AV 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 ST51A/ST75A/ST75AV: 03 and 04.
Table 19 – ST51A/ST75A/ST75AV Modbus Function Codes
Function Code
Description
03
Holding Register Read Only – Process Data
Holding Register Read/Write – Service Data
04
Read Input Register for all Process Data
Read Input Register for all Service “Start/Stop” Totalizer and Adjust K Factor Parameters
Refer to Table 20 (page 58), and Table 22 (page 64) for Modbus register information and engineering unit codes, respectively.
ST51A/ST75A/ST75AV Process Data Registers
Two data type registers are set up in the ST51A/ST75A/ST75AV 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.