Patent ID: 7746183

Claim:
An apparatus comprising: a plurality of ring oscillator blocks activated in response to an enable signal externally inputted thereto for outputting measurement result values; a decoder for selectively outputting one or more of the measurement result values from the ring oscillator blocks; and a statistics assistor for receiving output values from the decoder for a predetermined period and outputting a maximum value, a minimum value and an average value from the received values, wherein each of the ring oscillator blocks comprises: an enable stable unit for readjusting a period of the enable signal to a period of a system clock pulse and outputting the resulting enable signal; a ring oscillator for generating a pulse with a certain period based on a value of the enable signal outputted from the enable stable unit; an on-unit clock for selectively outputting the system clock pulse based on the value of the enable signal outputted from the enable stable unit; a rising counter operating at any one of a rising edge and falling edge of the pulse generated by the ring oscillator; a falling counter operating at any one of the rising edge and falling edge of the pulse generated by the ring oscillator; and a REF counter for receiving the system clock pulse outputted from the on-unit clock, the REF counter operating at a rising edge of the received system clock pulse.