A clock generator circuit generates a sequence of clock signals equally
phased from each other from a master clock signal. The clock generator is
formed by inner and outer delay-locked loops. The inner delay-locked loop
includes a voltage controlled delay line that delays a reference clock
applied to its input by a plurality of respective delays. Two of the
clock signals in the sequence are applied to a phase detector so that the
signals at the outputs of the delay line have predetermined phases
relative to each other. The outer delay-locked loop is formed by a
voltage controlled delay circuit that delays the command clock by a
voltage controlled delay to provide the reference clock to the delay line
of the inner delay-locked loop. The outer delay-locked loop also includes
a phase detector that compares the command clock to one of the clock
signals in the sequence generated by the delay line. The outer
delay-locked loop thus locks one of the clock signals in the sequence to
the command clock. As a result, all of the clock signals in the sequence
generated by the delay line have respective predetermined phases relative
to the phase of the command clock. One of the clock signals in the
sequence is selected by a multiplexer to clock a command data latch at a
time corresponding to the delay in coupling a command data bit to the
latch.