9400200990 Rev I DGC-2020 Modbus™ Communication i
APPENDIX B • MODBUS™ COMMUNICATION
TABLE OF CONTENTS
INTRODUCTION..........................................................................................................................B-1
General Overview ..................................................................................................................B-1
Intended Use of the Communications Protocol .....................................................................B-1
DETAILED DESCRIPTION OF DGC-2020 MODBUS PROTOCOL............................................B-1
Modbus Protocol Overview....................................................................................................B-1
Serial Transmission Details ...................................................................................................B-2
Message Framing / Timing Considerations ...........................................................................B-2
Error Handling and Exception Responses.............................................................................B-2
DETAILED DGC-2020 MESSAGE DEFINITION .........................................................................B-2
Device Address......................................................................................................................B-2
Function Code and Data Block ..............................................................................................B-2
DATA FORMATS .........................................................................................................................B-5
Short Integer Data Format (INT8)..........................................................................................B-5
Integer Data Format (INT16)..................................................................................................B-5
Long Integer Data Format (INT32).........................................................................................B-6
Floating Point Data Format....................................................................................................B-6
Double Precision Data Format (DP) ......................................................................................B-7
Triple Precision Data Format (TP) .........................................................................................B-7
Error Check ............................................................................................................................B-7
Interdependence of Preset Multiple Register Data................................................................B-7
MAPPING - DGC 2020 Parameters into MODICON ADDRESS SPACE....................................B-8
Table Conventions.................................................................................................................B-8
Legacy Parameter Table........................................................................................................B-8
Current Parameter Table .....................................................................................................B-21
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