DATA PROCESSOR

PURPOSE: To attain the processing of a byte mode and a non-byte mode by connecting an extended unit with serial links and parallel buses to execute data transfer and a processing related with the data transfer on the parallel buses. CONSTITUTION: An extended unit 22 is provided with a means which executes the initial selection of a byte mode device, a device reconnecting means, a means which transfers a control frame having a device address to a channel 15, a means which continues data transfer in response to a continuous frame from the channel 15 and a means which transfers a frame indicating the disconnection of control units 19a and 19b to the channel 15. Then, the reception of the frames on serial links 18 and 20 of the channel 15, data transfer on parallel buses 24 and the processing related with the data transfer are executed. Therefore, the processing of the byte mode and the non-byte mode is executed by this extended unit 22.