BIDIRECTIONAL BUS CONTROL UNIT

PROBLEM TO BE SOLVED: To eliminate the need to decide a function stop block and eliminate the erasure of a memory by resetting function blocks in order from a block which is not under memory control if one function block causes bus abnormality. SOLUTION: A microcomputer 1 which has a bidirecitonal bus 2 of one system and plural reset terminals controls plural function blocks 3 5. Then reset lines are provided by the function blocks 3-5 and if the bus line becomes abnormal (for example, a communication is disabled owing to the suction of the current of the bus line by the function block 4), the blocks 3 and 4 having no memory are reset first in order. When the bus recovers from the abnormality, the system in put back into normal operation. Consequently, the blocks are efficiently reset so that the destruction of memory data is evaded as much as possible, and the system can be put back into the normal operation.