US 7,590,025 B2
Systems and methods for clean DQS signal generation in source-synchronous DDR2 interface design
Yong Wang, Shanghai (China); Liang Zhang, Shanghai (China); and Xin Liu, Shanghai (China)
Assigned to Integrated Device Technology, Inc., San Jose, Calif. (US)
Filed on Dec. 19, 2007, as Appl. No. 12/4,177.
Prior Publication US 2009/0161452 A1, Jun. 25, 2009
Int. Cl. G11C 8/18 (2006.01)
U.S. Cl. 365—233.1  [365/193] 15 Claims
OG exemplary drawing
 
8. A digital system for generating a signal to synchronize DQ data transfer in memory interface design, the apparatus comprising:
a first input configured to receive a strobe signal having a preamble period before and post-amble period after data transfer burst synchronization signal edge transitions;
a second input configured to receive a signal indicating the timing location of the strobe signal preamble period;
a counter configured to count edge transitions of the received strobe signal that correspond with DQ data transfer following the preamble period and generate a corresponding output signal;
a first digital circuit configured to receive the output signal from the counter and a delayed output signal from the counter and to generate an output signal indicating the completion of strobe signal edge transitions corresponding with DQ data transfer based on the result of a logical AND operation performed on the output signal from the counter and the delayed output signal from the counter;
a trigger configured to assert a signal indicating when the strobe signal enters and exists the preamble and post-amble periods respectively, based on the signal received from the first digital circuit and the second input configured to receive a signal indicating the timing location of the strobe signal preamble period; and
a second digital circuit configured to receive the signal generated by the trigger and the received strobe signal and generate a output signal based on the result of a logical AND operation performed on the signal generated by the trigger and the received strobe signal.