US Patent 10346332 Slave device

When a data request is sent from a master device in master-slave communication, a slave device determines whether a piece of data requested by the data request among data stored on the slave device side has been updated after previous transmission of the piece of data. If the piece of data has been updated, the slave device sends the updated piece of data as a response to the data request. If the piece of data has not been updated, the slave device suspends a response to the data request. Thus, a communication system is built which can reduce network processing load and the volume of communication data in the case where the master device periodically acquires data from the slave device.