Abstract: A jumper (60) is provided as a control input means for switching operation modes of a CardBus controller (42). Also, a bidirectional bypass path (40A, 66, 58A) is provided in parallel with the controller. When a passthrough mode signal (64) from the jumper exhibits an inactive state, the controller is enabled for operation and the bypass path is disabled for operation, thereby to cause the controller to be operated in its normal mode. On the other hand, when the passthrough mode signal exhibits an active state, the controller is disabled for operation and the bypass path is enabled for operation, thereby to cause predetermined signals on PCI bus signal lines (40A), or signals on CardBus signal lines (58A) corresponding with the predetermined signals to be output on the CardBus or PCI bus as they are via the bypass path. In order to inspect transactions on the PCI bus, a PCI bus analyzer or exerciser is connected to a PC card slot (44A), to which the bypass path is connected.