In-Situ Aqua TROLL 400 Modbus and SDI-12 Reference Guide - Manual (Page 63)

Byte Offset Field Description Type Value
18-21 Device Serial Number ulong
22-23 Max Message/Response Size
(bytes)
ushort
24-25 Max Baud Rate ID ushort
26-27 CRC
The specific field values such as device ID, baud ID, etc. are documented in the sections that
follow.
8.11 Instrument Manufacturer Data Types
Modbus defines all I/O in terms of 2 byte blocks called registers. Modbus does not formally
define blocks for floating point values or strings. In the manufacturer’s implementation, these
fundamental types and others are handled by combining two or more registers. The
manufacturer data type implementations are defined in the following sections.
8.11.1 Short
A 2-byte signed integer contained in a single register data address. IEEE standard.
Where S = sign bit
8.11.2 Unsigned Short
A 2-byte unsigned integer contained in a single register data address. IEEE standard.
8.11.3 Long
A 4-byte signed integer contained in two register data address’s. IEEE standard.
Where S = sign bit
Byte 2 Byte 3 Byte 1 Byte 0
SXXX XXXX XXXX XXXX MSB LSB XXXX XXXX XXXX XXXX
Byte 1 Byte 0
XXXX XXXX XXXX XXXX
MSB LSB
Byte 1 Byte 0
SXXX XXXX XXXX XXXX
MSB LSB
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