EV/DV300 Series Power Meter
V:2.0 Revised October 2018
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Chapter 4: Communications
4.1 Modbus Protocol Introduction
The Modbus RTU protocol is used for communication in EV300 series meter. The data format
and error check field are defined in Modbus protocol. The half-duplex query and respond
mode is adopted in Modbus protocol. There is only one master device in the communication
net. The others are slave devices waiting for the query of the master.
1. Transmission mode
The transmission mode defines the data structure within a frame and the rules used
to transmit data. The mode is defined in the following table that is compatible with
Modbus RTU mode.
Coding System
8-bit binary
Start bit
1
Data bits
8
Parity
NO parity
Stop bit
1 bit
Error checking
CRC (Cyclical Redundancy Check)
2. Protocol
2.1 Frame
The message frame should contain four parts, address of the slave device, function
code define action of slave device, data of action and error check field.
Table 4.1 Data Frame
Address
Function
Data
Check
8-Bits
8-Bits
N x 8-Bits
16-Bits
2.2 Address field
The address field of a message frame contains eight bits. Valid codes are in the range
of 0-255 decimal. When a message is sent from a master to a slave device the function
code field tells the slave what kind of action to perform.
