AccuEnergy Acuvim II, User Manual

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This chapter will mainly discuss how to handle the meter via the communication
port using software. It is highly recommanded that previous chapters be read
before moving onto Chapter 5, a familiarity with Modbus would also be helpful.
6.1 Modbus Protocol Introduction
Modbus
TM
RTU protocol is used for communication in Acuvim II series meters.
Data format and error check methods 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 network. The others are slave devices,
waiting for the query of the master.
Transmission mode
The mode of transmission defines the data structure within a frame and the
rules used to transmit data. The mode is defined in the following which is
compatible with Modbus RTU Mode*.
Framing
Address Function Data Check
8-Bits 8-Bits N×8-Bits 16-Bits
Table 6-1 Data Frame Format
Address Field
The address field of a message frame contains eight bits. Valid slave device
Coding System 8-bit binary
Start bit 1
Data bits 8
Parity no parity
Stop bit 1
Error checking CRC check
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