Methods and computer program products for determining simultaneous switching induced data output timing skew

Abstract

A method of determining timing skew between data outputs of a memory device can include writing a predetermined data pattern to a memory device at a first operational frequency that is less than a normal operational frequency used to write non-predetermined data to the memory device. The memory device is read to output the predetermined data pattern therefrom at a second operational frequency that is greater than the first operational frequency and about equal to a normal operational frequency used to read non-predetermined data from the memory device. Timing skew is determined between outputs from the memory device based on the actual time when the predetermined data is provided from the memory device.

1 . A method of determining timing skew between data outputs of a memory device comprising:
 writing a predetermined data pattern to a memory device at a first operational frequency that is less than a normal operational frequency used to write non-predetermined data to the memory device;   reading the memory device to output the predetermined data pattern therefrom at a second operational frequency that is greater than the first operational frequency and about equal to a normal operational frequency used to read non-predetermined data from the memory device; and   determining timing skew between outputs from the memory device based on the actual time when the predetermined data is provided from the memory device.   
   
   
       2 . A method according  claim 1  wherein the predetermined data pattern is selected to generate delay in reading the memory device due to switching of voltage levels at the outputs of the memory device. 
   
   
       3 . A method according to  claim 2  wherein determining timing skew between outputs from the memory device comprises:
 setting a minimum delay time estimated to be when data would be output from the memory device without the delay due to switching;   measuring an output time when the predetermined data becomes valid at the outputs; and   determining the delay by subtracting the minimum delay time from the output time.   
   
   
       4 . A method according to  claim 1  wherein determining timing skew between outputs comprises determining the timing skew for each output of the memory. 
   
   
       5 . A data training method performed in a memory device which does not include an additional device for data training, the method comprising:
 (a) writing a predetermined data pattern to the memory device;   (b) reading a data pattern from the memory device; and   (c) determining a delay time in data transmission by measuring a delay time between the read data pattern and the predetermined data pattern,   wherein a speed at which the predetermined data pattern is written to the memory device is less than a normal operating speed of the memory device, and   a speed at which the data pattern is read from the memory device is equivalent to the normal operating speed of the memory device;   wherein (b) the reading of the data pattern comprises:   (b1) operating the memory device at the normal operating frequency; and   (b2) reading the data pattern from the memory device at the normal operating frequency; and   wherein (b) the reading of the data pattern further comprises (b2) selecting a pin of the memory device which performs data training.   
   
   
       6 . The data training method of  claim 5 , wherein (a) the writing of the predetermined data pattern comprises:
 (a1) operating the memory device at a frequency less than a normal operating frequency of the memory device; and   (a2) writing the predetermined data pattern to a predetermined cell of the memory device.   
   
   
       7 . The data training method of  claim 5 , wherein (b) the reading of the data pattern comprises:
 (b1) operating the memory device at the normal operating frequency; and   (b2) reading the data pattern from the memory device at the normal operating frequency.   
   
   
       8 . The data training method of  claim 7 , wherein (b) the reading of the data pattern further comprises (b2) selecting a pin of the memory device which performs data training. 
   
   
       9 . The data training method of  claim 5 , wherein (b) the reading of the data pattern further comprises (b3) setting a minimum delay time in data transmission. 
   
   
       10 . The data training method of  claim 9 , wherein (c) the determining of the delay time in data transmission comprises:
 (c1) measuring a delay time between the read data pattern and the predetermined data pattern;   (c2) determining the delay time in data transmission using the measured delay time and the minimum delay time; and   (c3) storing the determined delay time, and selecting another pin of the memory device when it is determined that all pins of the memory device are not checked.   
   
   
       11 . A computer program product for determining timing skew between data outputs of a memory device comprising a computer readable medium having computer readable program code embodied therein, the computer readable program product comprising:
 computer readable program code configured to write a predetermined data pattern to a memory device at a first operational frequency that is less than a normal operational frequency used to write non-predetermined data to the memory device;   computer readable program code configured to read the memory device to output the predetermined data pattern therefrom at a second operational frequency that is greater than the first operational frequency and about equal to a normal operational frequency used to read non-predetermined data from the memory device;   computer readable program code configured to determine timing skew between outputs from the memory device based on the actual time when the predetermined data is provided from the memory device.   
   
   
       12 . A computer program product according  claim 11  wherein the predetermined data pattern is selected to generate delay in reading the memory device due to switching of voltage levels at the outputs of the memory device. 
   
   
       13 . A computer program product according to  claim 12  wherein the computer readable program code configured to determine timing skew between outputs from the memory device comprises:
 computer readable program code configured to set a minimum delay time estimated to be when data would be output from the memory device without the delay due to switching;   computer readable program code configured to measure an output time when the predetermined data becomes valid at the outputs; and   computer readable program code configured to determine the delay by subtracting the minimum delay time from the output time.   
   
   
       14 . A computer program product according to  claim 11  wherein the computer readable program code configured to determine timing skew between outputs comprises computer readable program code configured to determine the timing skew for each output of the memory. 
   
   
       15 . A method of determining timing skew between data outputs of a memory device comprising:
 determining timing skew between outputs from the memory device based on a difference between the actual time when predetermined data is provided from the memory device and a minimum delay time.   
   
   
       16 . A method according to  claim 15  wherein the predetermined data is written to the memory device at a relatively slow speed in comparison to a speed at which the predetermined data is read from the memory device.