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Appendix E MODBUS Commands Series 24-HP Instruction Manual
IM-24-HP E-1
Appendix E Modbus Communication
Applicable Flow Meter Models
Sierra Innova-Mass® Mass Flow Meters, Models 240 and 241 with Modbus communication pro-
tocol and firmware version 3.00.02 and above.
Overview
This document describes the preliminary implementation of the Modbus communication protocol
for use in monitoring common process variables in the Sierra Innova-Mass® Vortex flow meter.
The physical layer utilizes the half-duplex RS-485 port, and the Modbus protocol.
Reference Documents
The following documents are available online from www.modbus.org.
Modbus Application Protocol Specification V1.1
Modbus Over Serial Line Specification & Implementation Guide V1.0
Modicon Modbus Protocol Reference Guide PI–MBUS–300 Rev. J
Menu Items
The following menu items are in the Output Menu and allow selection and control of the
Modbus communication protocol.
Address
When the Modbus protocol is selected, the Modbus address is equal to the user program-
mable device address if it is in the range 1…247, in accordance with the Modbus specifica-
tion. If the device address is zero or is greater than 247, then the Modbus address is inter-
nally set to 1.
Comm Protocol
The Comm Protocol menu allows selection of “Modbus RTU Even,” “Modbus RTU Odd,” or “Mod-
bus RTU None2,” or “Modbus RTU None1,” (non-standard Modbus) with Even, Odd and None re-
ferring to the parity selection. When even or odd parity is selected, the unit is configured for 8 data
bits, 1 parity bit and 1 stop bit; with no parity, the number of stop bits is 1 (non-standard) or 2.
When changing the protocol, the change is made as soon as the Enter key is pressed.