Patent ID: 7966468

Claim:
An apparatus for speculatively transferring a read request from a first clock domain to a second clock domain, said read request being compliant with a source synchronous read request protocol providing that said read request includes an address portion representing an address and an address strobe latching signal having a latching edge for latching said address portion and an address strobe occurring later in time than said address portion and said address strobe latching signal, said address strobe providing an indication of the validity of the read request, the apparatus comprising: a latch configured to latch said address portion from said first clock domain into said second clock domain in response to said latching edge of said address strobe latching signal; a pointer generator in said first clock domain to generate a write pointer in response to detecting said latching edge of said address strobe latching signal, said write pointer indicative of said read request and a safe clock edge in the second clock domain for crossing over said address portion into said second clock domain within a time window defined by a timing budget and jitter effects and adjusted by a checking module to select a safe time to return valid data; and request logic in said second clock domain configured to generate a read command to a memory responsive to said address portion and said write pointer; wherein said apparatus includes a first mode of operation to transfer said read request speculatively without validating said read request prior to synchronizing the read request into the second clock domain and prior to transferring the read request from the first clock domain to the second clock domain, said apparatus is configured to validate said read request subsequent to generating said read command; and wherein said apparatus includes a second mode of operation to transfer said read request from said first clock domain to said second clock domain subsequent to validating said read request.