Abstract: A multi-bus real-time message transmitter including a buffer memory for temporarily storing transmission messages, each of the transmission messages containing transmission time data designating time that the transmission message is to be sent, a plurality of transceivers connected to a plurality of bus lines, respectively, the plurality of transceivers sensing statuses of the corresponding bus lines, outputting the resultant bus line status data, sending the transmission messages stored in the buffer memory to the corresponding bus lines and sending messages received from the corresponding bus lines to the buffer memory, a timer for generating an interrupt signal at a fixed period and counting real-time, and a protocol processor for determining a network status in response to the bus line status data from the plurality of transceivers, setting a time window whenever the interrupt signal is generated by the timer, the time window having a time width different according to the determined network status, and co