A margin circuit for controlling skew between first and second signals in order to determine margin, includes a variable delay circuit and a margin controller. Based on a current code value, the delay circuit applies a delay to the second signal to generate a delayed second signal. The margin controller generates the current code value for the variable delay circuit to be any one of a plurality of available code values. In one embodiment, the margin circuit is a write margin circuit that generates a first clock signal and a delayed second clock signal used to generate transmit (TX) clock and data signals having a non-zero phase offset between them. In another embodiment, the margin circuit is a read margin circuit that applies a phase offset between receive (RX) clock and data signals to enable the RX clock signal to be used to recover data from the RX data signal.