A synchronous semiconductor memory device performs input/output of data in synchronization with an externally applied external clock signal or a data strobe signal in a test operation mode. An operation of an internal circuit in the test operation mode is performed in synchronization with a dock signal...http://www.google.com/patents/US6259647?utm_source=gb-gplus-sharePatent US6259647 - Synchronous semiconductor memory device allowing easy and fast test
