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64
Optidrive P2 Elevator User Guide V2.30
Serial communications
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17.
Serial communications
RS-485 communications
Optidrive P2 Elevator drive has an RJ45 connector on the front of the control panel. 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. Both connections can be used simultaneously.
The electrical signal arrangement of the RJ45 connector is shown as follows:
CAN-
CAN+
0 Volt
Optibus / Remote Keypad / PC Connection -
Optibus / Remote Keypad / PC Conn
+24 Volt Remote Keypad Power Supply
RS 485- Modbus RTU
RS 485+ Modbus RTU
Modbus RTU Communications
Modbus Telegram Structure
The Optidrive P2 Elevator drive 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 detailed in section 17.2.2 & 17.2.3 by subtracting 1 to obtain the correct Register address. The telegram structure is as
follows:-
Command 03 – Read Holding Registers
Master Telegram
Length
Slave Response
Length
Slave Address
1
Byte
Slave Address
1
Byte
Function Code (03)
1
Byte
Starting Address
1
Byte
1
st
Register Address
2
Bytes
1
st
Register Value
2
Bytes
No. Of Registers
2
Bytes
2
nd
Register Value
2
Bytes
CRC Checksum
2
Bytes
Etc...
CRC Checksum
2
Bytes
Command 06 – Write Single Holding Register
Master Telegram
Length
Slave Response
Length
Slave Address
1
Byte
Slave Address
1
Byte
Function Code (06)
1
Byte
Function Code (06)
1
Byte
Register Address
2
Bytes
Register Address
2
Bytes
Value
2
Bytes
Register Value
2
Bytes
CRC Checksum
2
Bytes
CRC Checksum
2
Bytes