RX631 the interrupt of usb's detach

The microcontroller is RX631,the USB module operates as host controller .
Peripheral equipment is mass stroage calss.the description of the interrupt of DTCHE is USB Disconnect detection Interrupt in RX631's datasheet .while USB is running unplug the Peripheral equipment  the  DTCH's interrupt is not occurred, the condition of this interrupt ? what is the interrupt when Peripheral equipment unplug ?