Mechanism for automatically aligning data signals and strobe signals on a source synchronous bus

Abstract

An apparatus is provided that compensates for misalignment on a synchronous data bus. The apparatus includes a replica radial distribution element, a bit lag control element, and a synchronous lag receiver that is configured to receive one of a plurality of radially distributed strobes and a data bit, and that is configured to delay registering of the data bit by a propagation time. The replica radial distribution element is configured to receive a first signal, and is configured to generate a second signal, where the replica radial distribution element comprises replicated propagation path lengths, loads, and buffering of a radial distribution network for a strobe. The bit lag control element is configured to measure a propagation time beginning with assertion of the first signal and ending with assertion of the second signal, and is configured to generate a value on a lag bus that indicates the propagation time. The synchronous lag receiver has a first plurality of matched inverters, a first mux, and a bit receiver. The first plurality of matched inverters is configured to generate successively delayed versions of the data bit. The first mux is coupled to the first plurality of matched inverters, and is configured to receive a value on a lag bus that indicates the propagation time, and is configured to select one of the successively delayed versions of the data bit that corresponds to the value. The bit receiver is configured to receive the one of the successively delayed versions of the data bit and one of a plurality of radially distributed strobe signals, and is configured to register the state of the one of the successively delayed versions of the data bit upon assertion of the one of a plurality of radially distributed strobe signals.