| 摘要 |
PURPOSE:To efficiently and easily perform an AC test with less number of input- output terminals exclusively used for the test, by constituting a ring oscillating circuit utilizing a two-way input-output terminal and internal logical circuit. CONSTITUTION:At the time of normal operation, a test mode signal arriving through a pin 27 exclusively used for test is ''1'' and an output buffer 26 is under a disable condition. Therefore, a two-way terminal 21 acts an an input terminal only and an input signal is propagated so an internal circuit as Sig1. On the other hand, a signal supplied through the pin 27 at the time of test mode becomes ''0''. Therefore, an input buffer 25, inverter elements 28-2n, and ouput buffer 26 are coupled in a ring and function as a ring oscillating circuit. When an oscillating frequency is observed from the two-way terminal 21 by utilizing this, the AC characteristic of the internal circuit can be presumed easily. |
