A first transparent latch receives a first synchronised
signal changing its
logic state synchronously with respect to a
clock signal. A second transparent latch receives a second synchronised
signal output by the first latch. When the
clock signal has a first
logic state the first latch has a non-responsive state and the second latch has a responsive state, and when the
clock signal has a second
logic state the first latch has the responsive state and the second latch has the non-responsive state. The change in logic state of a third synchronised signal output by the second latch is guaranteed to occur in a particular half-cycle of the
clock signal, irrespective of process /
voltage / temperature (PVT) variations of the circuitry.
Clock recovery circuitry may have rising-edge and falling-edge latches; circulating
control pattern verification circuitry; data synchronising circuitry for converting parallel data clocked by a first
clock signal into serial data clocked by a second
clock signal asynchronous with the first clock signal; and
data recovery circuitry for producing an offset clock signal which suits a data eye shape of a received serial
data stream.