Chapter 8 Appendix
Appendix A: Serial Communications
AC drive, provide the RS485 communication interface, and adopt the ModBus communicatio-
n protocol of international standard to make master- slave communication. Users can realize
centralized control by PC/ PLC, upper computer controlling and so on( set the controlling co-
mmand, operation frequency, correlation function code parameters change, inverter working
state and fault information monitoring, etc. ) , so as to adapt to specific application requirem-
ents.
1.Protocol content
The Modbus serial communication protocol defines the frame content and using form of
asynchronous transmission in serial communication, including: host polling and broadcast
frame, slave response frame format; frame content of host organization includes: slave
address ( or the broadcast address) , performing commands, data and error checking, etc. ;
slave response is also using the same structure , content including: action confirmation, data
returning and error checking, etc. if error happens when slave is receiving frame, or cannot
achieve the requirements of the host, it will organize a fault frame as a response feedback to
the host.
2.Application way
AC drive access the controlling network of “single master multiple slave” with Rs232/RS485
bus.
3.Bus structure
( 1) The interface way RS485 hardware interface
( 2) Transmission mode
Asynchronous serial and half- duplex transmission mode. At the same time only one betwe-
en the host and the slave can send data and the other receives data. In the process of serial
asynchronous communication, data is sending in the form of message, and frame by frame.
( 3) Topological structure
Single master multiple slave system. Slave address set range from 1
～
247, 0 as the broadc-
ast address, andeach slave address in the network has uniqueness. This is the foundation of
guaranteeing Modbus serial communication.
4.Protocol specification
The communication protocol of AC drive is a kind of master-slave Modbus co-mmunication
protocol with asynchronous serial, and in the network only one device ( host) can establish-
protocol( called “query/ command”) . Other device ( slave) can only respond to “query/
command” of the host with the provided data, or make corresponding action according to the
-202-
C
h
a
p
te
r
8
Peaco Support FC280 Series VFD User Manual
www.peacosupport.com [email protected] Free Shipping Worldwide Reliable Supplier
PEACO SUPPORT
