Communication device, communication system and communication control method

A communication device comprising:

• a processor;
• and
• a communication part that is configured to communicate with one or more slaves, wherein the processor has a function of executing
• communication processing of causing the communication part to transmit a data frame including main data to the one or more slaves in a first period, and
• setting processing of setting N second periods, where N is an integer of 2 or more, within the first period and a slot for performing communication of sub-data other than the main data for each of the N second periods,
• the data frame includes the slot during a transmission period of the main data,
• the main data includes a plurality of main data pieces,
• the processor is configured to divide the plurality of main data pieces in the N second periods, the divided main data pieces being transmitted in the communication processing, and
• the processor is configured to set the second period based on at least one of the first period, a data size of the main data, and a data size of the sub-data in the setting processing.