Data Sheet
Copyright © Roboteq Inc. 2018. All Rights Reserved. i
Table of Contents
1. Introduction ....................................................................................................................................... 1
1.1 What is Modbus ...................................................................................................................................... 1
1.2 Modbus object types .............................................................................................................................. 1
1.3 Protocol versions .................................................................................................................................... 1
1.4 Communication and devices ................................................................................................................... 2
1.5 Frame format .......................................................................................................................................... 2
1.5.1 Modbus RTU frame format ............................................................................................................. 2
1.5.2 Modbus ASCII frame format ............................................................................................................ 3
1.5.3 Modbus TCP frame .......................................................................................................................... 3
1.6 Function Codes ....................................................................................................................................... 3
2. Roboteq Implementation ................................................................................................................... 4
2.1 Supported Functions ............................................................................................................................... 4
2.1.1 Read Input Registers (0x04)............................................................................................................. 4
2.1.2 Write Multiple Holding Registers (0x10) ......................................................................................... 5
2.1.3 Exception responses ........................................................................................................................ 5
2.2 Supported Modes ................................................................................................................................... 7
2.2.1 Modbus RTU over TCP (2)................................................................................................................ 7
2.2.2 Modbus TCP (1) ............................................................................................................................... 8
2.2.3 Modbus RS232/RS485 ASCII ............................................................................................................ 9
2.3 Register Address Calculation ................................................................................................................ 10
2.4 Controller Configuration ....................................................................................................................... 11
3. Appendix A: Commands Mapping ..................................................................................................... 12
3.1 Command Mapping .............................................................................................................................. 12
3.2 Query Mapping ..................................................................................................................................... 12
4. Appendix B: CRC Calculation ............................................................................................................. 14