9400200990 Rev K
DGC-2020 Modbus
Communication
i
APPENDIX B
MODBUS COMMUNICATION
TABLE OF CONTENTS
Modbus COMMUNICATION .........................................................................................B-1
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
Device Address Field......................................................................................................................B-1
Function Code Field........................................................................................................................B-1
Data Block Field..............................................................................................................................B-2
Error Check Field............................................................................................................................B-2
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
Read Holding Registers..................................................................................................................B-3
Return Query Data..........................................................................................................................B-3
Preset Multiple Registers, Non-Broadcast & Broadcast.................................................................B-4
Preset Single Register, Non-Broadcast & Broadcast .....................................................................B-4
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-6
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-22
Breaker Management ...................................................................................................................B-22
Bias Control Settings ....................................................................................................................B-23
Pulse Outputs ...............................................................................................................................B-24
Bus Condition Detection ...............................................................................................................B-24
Senders.........................................................................................................................................B-25
System Configuration and Status .................................................................................................B-25
Control ..........................................................................................................................................B-28
Communication.............................................................................................................................B-29
Protection......................................................................................................................................B-29
Alarms...........................................................................................................................................B-33
Metering ........................................................................................................................................B-36
Tables Table B-1. Exception Response Codes ....................................................................................................B-2
Table B-2. Floating Point Format...............................................................................................................B-6
Table B-3. Legacy Parameter Table .........................................................................................................B-9
