Method and device for masking ringing in a ddr sdram

Abstract

A DDR SDRAM operates at a double data rate by accessing the bursts of data having a burst length in accordance with the rising and falling edges of each pulse of a DQS signal. A ringing may occur in the DQS signal causing write failures. To mask the ringing, a DQS buffer generates a first access signal at the rising edge of each DQS pulse generated in presence of the data burst. The DQS buffer also generates a second access signal at the falling edge of each DQS pulse. Each of the first and second access signals includes a finite number of pulses based on the total number of rising and falling edges of the DQS signal. Two consecutive data bursts are accessed together for a write operation for each pair of the consecutive first and second access signals. After accessing all data bursts, a mask time is calculated to disable the DQS buffer, by which the ringing is masked.