Lossless transfer of events across clock domains

Abstract

Transfer circuits () for monitoring in a monitor clock domain target events that occur in a target clock domain () are disclosed. Some embodiments () impose significant constraints on the domain clocks and include: an event detector (); a sending circuit () that changes the value of a request signal () with each event; and a receiving circuit () that detects changes in the request signal. Other embodiments work for a broader range of clocks and include: a counter () that generates an incremental count () of event occurrences while a transfer is taking place; sending and receiving registers () for the incremental count; the request sending and receiving circuits (), where the request signal changes value for each transfer of the incremental count; and sending and receiving circuits () for an acknowledgement signal.