| 摘要 |
<p>PURPOSE:To evaluate a ring oscillator by providing a logic gate circuit for first and second selecting circuits and a feedback resistor between the output of the logic gate circuit and an input for external oscillation and defining the output of the logic gate circuit as an output for external oscillation. CONSTITUTION:An AND gate 12 defines the input signal of an external input terminal X1 and an output signal A of a ring oscillator 30 as inputs. When a programmable read only memory (PROM) cell is written or read and a high level is inputted to an oscillator control signal 14, the external input terminal X1 of the oscillator is set to the high level and the NAND gate 12 is turned to an active state. At such a time, when the output signal A of the ring oscillator 30 is changed from a low level to the high level, the reverse phase to the output of the ring oscillator 30 is outputted to the output of the NAND gate 12, namely, to an external output terminal X2 of the oscillator. Thus, the write current or read current of the PROM can be evaluated while being related to a ring oscillator frequency and a manufacture process condition.</p> |
