Method and circuit for providing handshaking to transact information across multiple clock domains

Abstract

A method and circuit for handshaking information across multiple clock domains within an electronic system. The environment of the present invention includes an electronic or computerized system having at least two subsystem domains (a first domain and a second domain) operating at different clock rates (a first clock and a second clock). The present invention includes a handshake circuit coupled between the first and second domains for providing the required handshaking signals to control the transfer of data between the first domain (master) and the second domain (slave). An information bus is coupled between the domains. The handshake circuit is such that double synchronization is not required and the design of the present invention is dynamic such that it is operable between clock domains of varying frequency. The present invention utilizes the asynchronous input of a flip-flop circuit to catch the pertinent handshaking signals between clock domains. The D input and the clock input of the flip-flop circuit are coupled to the master clock domain and the master clock domain receives a ready signal back. When ready is asserted, the master domain may assert a request (from the master domain) over the D input and hold data. The Q output is coupled to a request (to the slave domain) which is also coupled as an input to a NOR circuit. An acknowledge signal is coupled to the asynchronous flip-flip input as a clear and also coupled to the second input of the NOR circuit. The output of the NOR circuit generates the ready signal.