Patent ID: 7622953

Claim:
A selector having a test mode to detect a fault, said selector comprising: a data output terminal; a test output terminal; a first tri-state device having an output connected to said data output terminal; a second tri-state device having an output connected to said data output terminal; and a tester operable to output a first logical value or a second logical value to said test output terminal according to whether a voltage of said data output terminal is higher or lower than a threshold value in the test mode, said tester being operable to convert an intermediate potential occurring in said data output terminal into the first logical value and to output the first logical value to said test output terminal when said first tri-state device outputs a high level signal to said data output terminal and said second tri-state device outputs a low level signal to said data output terminal in the test mode, wherein said tester includes: a semiconductor switch that has one end connected to said data output terminal, is on in the test mode, and is off when not in the test mode; and an inverter having an input connected to an other end of said semiconductor switch and an output connected to said test output terminal.