AccuEnergy AcuDC 241, User Manual

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This chapter will mainly discuss how to operate the meter via communication port using
software. To master this chapter, you should be familiar with Modbus and read other
chapters of this manual to make sure that you have a good understanding of the functions
and applications of this product.
This chapter includes: Modbus protocol, communication format and communication
address table.
4.1 MODBUS-RTU Protocol
Modbus RTU protocol is used for AcuDC 240's communication. Data format and error check
methods are defined in Modbus protocol. The half duplex query and respond mode is
adopted in Modbus protocol.
Modbus allows master device (PC, PLC etc.) to communicate with slave devices, it will not
allow data exchange between slave devices. Therefore, terminal devices will not engage the
communcation link at initialization, only responsed to the master’s request.
1. Transmission mode
The mode of transmission defines the data structure within a frame and the rules used to
transmit data.

Coding System 8 bit

Start Bit 1 bit

Data Bits 8 bit

Parity Even/Odd/None 2/None 1

Stop Bit 1/2 bit

Error Checking CRC