Optical glass containing bismuth oxide having good defoamability. Operation mode setting means incorporated in the electronic device executes signal assignment on a plurality of data pins peculiar to an operation mode indicated by the acquired operation mode information, thereby switching a data transfer width, and allowing the card-shaped device to operate in the operation mode. Each of the child stations sends a corresponding maintenance signal if necessary, and the parent station controls state transition by using the maintenance signal concerning on the mini slot signal for each of the child stations.