PURPOSE: To attain the control of two devices different from the basic specification by means of a common controller by giving a function identifying a device to the controller and allowing a host system to recognize the state of the device connected to the controller by loading its identification signal.

CONSTITUTION: Before a host system 2 gives a command controlling devices FD0W3 actually, the host system 2 senses at first the content of a device identification SW31. The host system 2 compares the content of its identification signal with a device number to be controlled and recognizes which of an A type device of a device 48 TPI or a B type device of 96 TPI the device number is. In order to initialize an FDC33 and a VFO34 into a proper state, a command is given to an initial set register 32. When each LSI of FDC33 and VFO34 is initialized, the host system 2 executes conventional READ and WRITE. The initializing of load FC33 and VFO34 for the identification signal minimizes the effect of the floppy device on access time.