Expanded operating frequency synchronous semiconductor memory device having wave pipeline structure and wave pipeline control method thereof

Abstract

Synchronous semiconductor memory devices and methods of operating are provided. The device has a latency N and includes a memory cell array, a stack unit having N storage units and a frequency detector that provides an output signal based on the relationship of the frequency of operation clock to a predetermined frequency. A control circuit controls the stack unit in response to the output signal of the frequency detector. The control circuit latches data read from the memory and controls the stack unit so that the latched data is stored from a clock cycle when a read command is sent until an N-th cycle afterwards if the clock frequency is greater than the predetermined frequency and delays the latched data for one cycle and controls the stack unit so that the delayed data is stored from one cycle after the read command is sent until an N+1 cycle afterwards.