A communication control circuit that performs the process of receiving a
response to send data in synchronous transfer mode within a certain
period of time without using an external control circuit. A permissible
time calculation section calculates permissible time for receiving
response data corresponding to send data sent to each of communication
nodes connected to a serial bus from data length of the send data, data
length of the response data, and a number of the communication nodes to
which the send data is sent on the basis of communication cycles
specified in the synchronous transfer mode. A response time management
section determines whether the response data received as a response to
the send data sent via the serial bus is received within the permissible
time calculated by the permissible time calculation section. As a result,
time taken to receive the response data corresponding to the send data is
guaranteed.