Semiconductor memory device having fixed CAS latency in normal operation and various CAS latencies in test mode

摘要

A semiconductor memory device having a fixed CAS latency during a normal operation and various CAS latencies during a test mode. The semiconductor memory device a master signal generator for generating a master signal in response to a power-up signal and a latency test signal. A plurality of fuse information units generate fuse information signals in response to the power-up signal and the master signal. A plurality of mode register set (MRS) address information units receive address bits during an interval where an address window signal is activated to generate MRS address latch signals in response to a MRS addressing signal. A CAS latency determining unit generates CAS latency select signals in response to the fuse information signals and the MRS address latch signals, wherein the CAS latency select signals provide a fixed CAS latency during a normal mode of operation of the semiconductor device and varying CAS latencies during a test mode of operation of the semiconductor device.