>In many cases, metastability in flip-flops can be avoided by ensuring=20 >that the data and control inputs are held constant for specified=20 >periods before and after the clock pulse, called the setup time (tsu)=20 >and the hold time (th) respectively. These times are specified in the=20 >data sheet for the device, and are typically between a few nanoseconds=20 >and a few hundred nanoseconds for modern devices. It seems that the "nanoseconds" in above paragraphs should have been "picoseconds". As an example, for a DDR2 SDRAM device such as Micron MT47H64M8 the DQ = input setup time tDS and input hold time tDH relative to DQS are 300ps and 175ps respectively. Regards, Abe Riazi ServerWorks ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu