Circuits, methods, and apparatus that prevent control signals from
changing state while the control signals are being used to delay a read
strobe signal. An exemplary embodiment of the present invention provides
a control circuit that provides a plurality of control bits to a delay
line, where the delay line delays or phase shifts a read strobe signal a
duration, where the duration depends on the state of the control bits.
The delayed read strobe signal is used to clock one or more data
registers. To avoid undesired changes in the duration that the read
strobe signal is delayed, the control bits are retimed before being
provided to the delay line. A specific embodiment waits for an edge of
the strobe signal to be output by the delay line before providing the
control bits to the delay line. Another specific embodiment waits until
no edge of the strobe signal is being delayed by the delay line before
providing the control bits to the delay line.