Cycle independent data to echo clock tracking circuit
First Claim
1. A memory system for a high speed double data rate (DDR) memory which generates a data signal and an echo clock signal, comprising:
- a memory controller clocked by a master clock signal;
a random access memory (RAM) array receiving input from said memory controller and outputting a global data signal;
a comparator for receiving the global data signal and the master clock signal to determine a delay timing there between; and
a variable delay circuit for receiving said delay timing signal and generating a delayed pipelined clock signal for simultaneously latching out said data signal and said echo clock signal.
1 Assignment
0 Petitions
Accused Products
Abstract
A comparator and variable delay circuit are provided to maintain the tracking between data and echo clocks in a double data rate (DDR)RAM device. This is accomplished by providing a global data signal (dummy data signal) that tracks with the actual memory array data. This global data signal is compared to the timing of the RAM clock (CLOCK) to determine a delay time between the two by which the pipeline clocks (CLKRISE/CLKFALL) must be delayed. As a result, the pipeline clocks are pushed out as needed so that they always transition after the array data arrives at the output latch. Therefore, as cycle time decreases, both echo clocks and data are pushed out identically and maintain their required tracking.
75 Citations
7 Claims
-
1. A memory system for a high speed double data rate (DDR) memory which generates a data signal and an echo clock signal, comprising:
-
a memory controller clocked by a master clock signal; a random access memory (RAM) array receiving input from said memory controller and outputting a global data signal; a comparator for receiving the global data signal and the master clock signal to determine a delay timing there between; and a variable delay circuit for receiving said delay timing signal and generating a delayed pipelined clock signal for simultaneously latching out said data signal and said echo clock signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
Specification