Abstract: In order to solve the communication problem between the 32-bit MCU(Microcontroller Unit) and the DC
(Direct Current) governor，a communication method and implementation process based on the Modbus bus protocol
is proposed． The 32-bit MCU selects the STM32F103 chip as the communication host，and the DC governor uses
the ETD DC790P as the communication slave． The method can realize the communication structure of a host multi-
slave，and realizes communication between a 32-bit MCU host and a plurality of DC governor slaves． The host
sends a command to the slave through the protocol，and the slave receives the command to make an action and
responds to the host through the protocol． Ｒepeated experiments have proved that the communication method based on Modbus protocol can accurately realize the communication between the host and multiple slaves，and can
accurately realize the control of the motor speed and torque of the 32-bit MCU． And the Modbus implementation
method has the advantages of high stability，strong anti-interference ability and high portability．

Key words: Modbus bus protocol, direct current (DC) governor, STM32 chip, master-slave communication