Despatch Protocol 3 Modbus Communications - Manual (Page 12)

A BOUT T HIS M ANUAL Modbus Programming Manual
12 Version 2
Copyright © 2012 by Despatch Industries.
All rights reserved. No part of the contents of this manual may be reproduced, copied or transmitted in any form or by any
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retrieval systems without the written permission of Despatch Industries, unless for purchaser's personal use.
The Modbus parameter register addresses are detailed in the following sections.
The Access column indicates if a parameter is read only (RO) or if it can also be written to
(R/W).
Note:
Some parameters that do not apply for a particular configuration will accept reads and
writes. Read only parameters will return an exception if an attempt is made to write values
to them.
1.4.8. Data Formats
Data can be read or written in three formats: Integer Only, Integer with 1 Decimal Place and
Floating Point Number.
The Modbus Address column shows the register address for each parameter in integer format.
Other formats can be calculated from the Integer Only address.
When working in Hexadecimal, the format calculations are:
Address for Integer with 1 Decimal Place = Integer address plus 0x4000
Address for Floating Point = Integer address multiplied by 2, plus 0x8000
When working in Decimal, the format calculations are:
Address for Integer with 1 Decimal Place = Integer address plus 16384
Address for Floating Point = Integer address multiplied by 2, plus 32768
Example Register Address Calculations
Calculating Parameter Register Addresses
Integer Only Integer+1 Floating Point
Register Address
Calculation (hex) Address Address + 0x4000 Address x 2 + 0x8000
(dec) Address Address + 16384 Address x 2 + 32768
Address Example:
(For Process Variable) (hex) 0x0407 0x4407 0x880E
(dec) 1031 17415 34830
Data Value Returned:
If actual Value = 23.9 decimal (hex) 0x00, 0x17 0x00, 0xEF
0x41, 0xBF, 0x33, 0x33
(dec) 23 239
23.9 as floating decimal
Address Example:
(For Selected Setpoint) (hex) 0x101F 0x501F 0xA03E
(dec) 4127 20511 41022
Data Value Returned:
If Value = 1 (Alternative SP) (hex) 0x00, 0x01 0x00, 0x0A
0x3F, 0x80, 0x00, 0x00
(dec) 1 10 1.0
as floating decimal