| 摘要 |
PURPOSE:To achieve an easy switch inspection without requiring detection of a high-impedance state by allowing an off state of a switch for transmitting a signal to be inspected by H and L of an output signal line. CONSTITUTION:A unit switch 22 has AND gates 30-36 and an OR gate 40 and then an OR gate 44 and AND gates 42 and 46 at a path to a signal line Y. An input signal line consists of main lines X0-X3 and auxiliary lines X0'-X3', an output signal line consists of a main line Y0 and an auxiliary line Y0', and then selection information signal lines O0-O3 are input. Then, the signals X0-X3 are input to the corresponding gates 30-36 along with the signals O0-O3 and the output is connected to a signal line Y0 through a gate 40. On the other hand, the signal lines X0'-X3' and O0-O3 are input to the gates 42 and 44 and are connected to the signal line Y0' through a gate 46, thus enabling it to be checked whether the switch is turned off or not by examining a state of the signal line Y0 when the state of the signal line Y0' is L (switch off). |
