A
video decoder (52, 152) including a digital-control oscillator (DCO) (60, 160) is disclosed. The DCO (60, 160) includes a first flying-
adder frequency synthesis circuit (74S) that measures an input
signal frequency, such as the horizontal
sync frequency of an input video
signal. A frequency control word (FREQ) is generated in response to this input
signal frequency, and is applied to a second flying-
adder frequency synthesis circuit (74), which in turn selects the appropriate phases for leading and trailing edges of the output
clock signal (PIX_CLK).
Phase tuning of the output
clock signal (PIX_CLK) can be effected by using an alternate flying-
adder frequency synthesis circuit (74′) architecture, in combination with a phase signal (PH) generated by a digital controller (61). Multiple phase-tuned sample clocks (PIX_CLK_A, PIX_CLK_B, PIX_CLK_C) can be similarly generated from multiple flying-adder frequency synthesis circuits (174A, 174B, 174C), each controlled by the frequency control word (FREQ) and a corresponding phase signal (PHA, PHB, PHC). Video
mode control logic (65, 165) can also be implemented by way of a similar DCO architecture. The DCO (60) may be used to generate a
clock signal at a large frequency multiple relative to the input signal, outside of the
video decoder context.