PURPOSE: To make it possible to control various transmission control procedures in one communication control module.

CONSTITUTION: In an initial state, processor 13 is controlled by firmware of ROM 14, and interprets commands of a central processing unit (arithmethic control unit and main memory), and reads and stores firmware data from the main memory into RAM 15. After that, the communication control module is mainly controlled by firmware of RAM 15. Firmware in RAM 15 can set the synchronous system of receiving/transmission by controlling URTLSI 17 as well as controls the transmission procedures. Further, the transmission clock can be generated in URTLSI, and also, the transmission speed can be freely set by firmware, so that it is possible to cope with various communication systems by using one communication control module.