Abstract: An on-chip clock waveform generator for generating from an externally supplied clock (EFI) an on-chip (internal) clock with a 50% duty cycle having a clock rate of 1/2, 1, or 2 times that of EFI, is based on a tapped delay line with a tap-to-tap differential delay of approximately 1% of the external clock (EFI) period. The waveform generator detects the tap at which a full period of delay occurs between delay line input and the tap. By knowing the tap for a first full period delay the generator determines the taps at which the 1/4, 1/2, and 3/4 period waveform states can be observed. The pulses corresponding to fractional periods, are used to generate standard pulse width streams that correspond to 1/4 period intervals. A programmed multiplexer/selector selects the proper sequence from these pulse streams to drive an RS flip-flop in order to produce the output 50% duty-cycle clock running at 1/2, 1, or 2 times the external (EFI) clock.

Abstract: An on-chip clock waveform generator for generating from an externally supplied clock (EFI) an on-chip (internal) clock with a 50% duty cycle having a clock rate of 1/2, 1, or 2 times that of EFI, is based on a tapped delay line with a tap-to-tap differential delay of approximately 1% of the external clock (EFI) period. The waveform generator detects the tap at which a full period of delay occurs between delay line input and the tap. By knowing the tap for a first full period delay the generator determines the taps at which the 1/4, 1/2, and 3/4 period waveform states can be observed. The pulses corresponding to fractional periods, are used to generate standard pulse width streams that correspond to 1/4 period intervals. A programmed multiplexer/selector selects the proper sequence from these pulse streams to drive an RS flip-flop in order to produce the output 50% duty-cycle clock running at 1/2, 1, or 2 times the external (EFI) clock.