Serial Communications - Invertek Drives Optidrive Series User Manual

10.

Serial communications

10.1. RS-485 communications
Optidrive HVAC has an RJ45 connector located within the wiring enclosure of the drive. This connector allows the user to set up a drive
network via a wired connection. The connector contains two independent RS485 connections, one for Invertek's Optibus Protocol and one for
Modbus RTU / BACnet.
The electrical signal arrangement of the RJ45 connector is shown as follows:
The Optibus data link is used for connection of Invertek peripherals and inter-drive communication. .
The Modbus interface allows connection to a Modbus RTU network as described below.
10.2. Modbus RTU Communications
10.2.1. Modbus Telegram Structure
The Optidrive HVAC2 supports Master / Slave Modbus RTU communications, using the 03 Read Holding Registers and 06 Write Single Holding
Register commands. Many Master devices treat the first Register address as Register 0; therefore it may be necessary to convert the Register
Numbers detail in section 12.2.2 by subtracting 1 to obtain the correct Register address. The telegram structure is as follows:-
Optidrive HVAC User Guide V2.00
Command 03 – Read Holding Registers
Master Telegram Length
Slave Address 1 Byte
Function Code (03) 1 Byte
st
1 Register Address 2 Bytes
No. Of Registers 2 Bytes
CRC Checksum 2 Bytes
Command 06 – Write Single Holding Register
Master Telegram Length
Slave Address 1 Byte
Function Code (06) 1 Byte
Register Address 2 Bytes
Value 2 Bytes
CRC Checksum 2 Bytes
www.invertekdrives.com
Not Used
Not Used
0 Volt
Optibus / Remote Keypad / PC Connection -
Optibus / Remote Keypad / PC Connection +
+24 Volt Remote Keypad Power Supply
RS 485- Modbus RTU / BACnet
RS 485+ Modbus RTU / BACnet
Warning:
This is not an Ethernet connection.
Do not connect directly to an
Ethernet port.
Slave Response
Slave Address
Function Code (03)
Starting Address
st
1 Register Value
nd
2 Register Value
Etc...
CRC Checksum
Slave Response
Slave Address
Function Code (06)
Register Address
Register Value
CRC Checksum
Length
1 Byte
1 Byte
1 Byte
2 Bytes
2 Bytes
2 Bytes
Length
1 Byte
1 Byte
2 Bytes
2 Bytes
2 Bytes
45