Rtu Mode - INVT Goodrive3000 Series Operation Manual

Goodrive3000 series medium voltage VFD
Master
Shielded twisted pair
Converter
RS cable max.
GND
PC
Figure 8.5 is the star connection. Terminal resistor should be connected to the two devices which have
the longest distance. (1# and 15#device)
It is recommended to use shield cables in multiple connection. The basic parameter of the devices, such
as baud rate and digital check bit in RS485 should be the same and there should be no repeated
address.

8.3.2 RTU mode

8.3.2.1 RTU communication frame format
If the controller is set to communicate by RTU mode in Modbus network every 8bit byte in the message
includes two 4Bit hex characters. Compared with ACSII mode, this mode can send more data at the
same baud rate.
Code system
· 1 start bit
· 7 or 8 digital bit, the minimum valid bit can be sent firstly. Every 8 bit frame includes two hex characters
(0...9, A...F)
· 1 even/odd check bit . If there is no checkout, the even/odd check bit is inexistent.
· 1 end bit (with checkout), 2 Bit(no checkout)
Error detection field
· CRC
The data format is illustrated as follows:
A+
B-
A+ B-
1# 2#
Figure 8.3 Chrysanthemum connection
485 +
485-
Ground
RS232- 485
INVT
VFD
length 15m
:
Address 1
Figure 8.4 Chrysanthemum connection applications
1#
32#
Figure 8.5 Star connection
3#
485+
485 -
Ground Ground
INVT
VFD
Address 2 Address n
15#
-248-
MODBUS protocol
31#
120Ω
485 +
Terminal
resistor
485-
INVT
VFD