Rtu Mode - INVT Goodrive 310-UL Series Operation Manual

GD310-UL series VFD
Figure 10-5 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.

10.3.2 RTU mode

10.3.2.1 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 below:
11-bit character frame (BIT1–BIT8 are the data bits)
Start bit BIT1
10-bit character frame (BIT1–BIT7 are the data bits)
Start bit BIT1
32 #
Figure 10-5 Star connection
BIT2 BIT3 BIT4
BIT2 BIT3 BIT4
1 #
Main control
devices
15 #
BIT5 BIT6 BIT7
BIT5 BIT6
-192-
Communication protocol
BIT8 Check bit End bit
BIT7 Check bit End bit