| 摘要 |
PURPOSE:To make it possible to easily select LSI from the outside by measuring AC characteristics by an oscillation frequency meter, by oscillating the critical pluse of a logical circuit in LSI. CONSTITUTION:A NAND circuit 29, AND circuits, NAND circuits 22, 20 and an OR circuit 26 are connected by connections 102, 103, 105, 106 to form a loop path and an oscillator circuit controllable by the signal of a terminal 59 is constituted. Now, when the terminal 59 is fixed to ''0'', the output of the NAND circuit 29 comes to ''1'' and, therefore, the input from the connection 102 from the AND circuit comes to ''1''. Next, when the terminal 59 is fixed to ''1'' and terminals 51-56, 58 to ''1'' while terminals 55, 57 to ''0'', the loop path consisting of the connections 102, 103, 105, 106 is oscillated. If this oscillation frequency is measured from the outside by an oscillation frequency meter, the AC characteristics of a logical circuit 2 can be calculated.
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