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SIF5600 - Manual - 03 - 2008
8.4 APPeNDIX A4 - MODBUS PrOtOcOL
Thytronic SIF5600M (v 2.02b) - Serie-N system - 31/05/2005
SIF5600M Protection relay: ModBus Map - rev. 0101
CONTENTS (v1.00-16.07.04)
Section 1 INTRODUCTION
Section 2 DATA ORGANIZATION
2.1 General
2.2 DATA type
2.3 DATA interface Modbus protocol
Section 3 MODBUS
3.1 General
3.2 Modbus communication
3.3 Standard message framing
3.4 CRC: Cyclical Redundancy Check
3.5 Transmission order of data elements
3.6 Function 03: Read WREG
3.7 Function 04: Read RREG
3.8 Function 06: Write single register WREG
3.9 Function 16: Write single or multiple register WREG
3.10 Function 08: loopback diagnostic test
3.11 Exception responses
Section 4 DATA STRUCTURE FORMAT
4.1 Format description
4.2 Format description example
Section 5 MODBUS COMMUNICATION EXAMPLE
5.1 WREG writing in Modbus communication
5.2 WREG reading in Modbus communication
Section 6 RREG structures description
Section 7 WREG structures description
Section 8 Command messages index
Section 9 Defaults index
Section 1 INTRODUCTION
The protection implements Modbus RTU protocol in remote RS485 half-duplex or local RS232 connection.
The following operation are supported:
- data reading
- configuration parameters reading and modifying
- command actuation
- communication network test
Section 2 DATA ORGANIZATION
2.1 General
Data are structured in WORD, or REGISTERS according to ModBus terminology:
data registers are always 16 bit (two bytes) wide.
In the afterwards only the term “register” will be used.
Two class of registers are provided:
- class RREG: read only registers
- class WREG: read/write registers
2.2 Data type
Five tipologies of basic data are employed:
- INT Stands for numerical values within 0...65535 range.
ModBus maps it into one register.
- LONG Stands for numerical values inside range 0...4294967295 max.
ModBus maps it into two contiguous registers.
- ENUM Single selection of one of N elements, inside range 0,1,2 ... 65535 max.
ModBus maps it into one register.
- B16 Multiple selection of some of N elements, with N(max) = 16.
Each bit stands for one element: 0=off, 1=on.
ModBus maps it into one register.
- B32 Multiple selection of some of N elements, with N(max) = 32.