Salicru CV30, Руководство пользователя, Страница: 101 / 140

Communication protocol 101 - 140
Figure 2 Chrysanthemum connection applications
Figure 3 is the star connection. Terminal resistor should be connected to the two devices which have the
longest distance. (1# and 15#device)
Figure 3 star connection
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.
7.2.2 RTU mode
7.2.2.1 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 digital bits)
Start bit BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7 BIT8 Check bit End bit