Metastability in Flip Flops and logic circuits

Many faults in digital circuit design, specially those using flip flops can be traced to the phenomenon of metastability. It is something that for a long time was not even recognized as an error source. However, a number of design engineers including the author of this article have personally experienced the tragedy of logic failure owing to metastability. In most instances the failure is hard to spot and can take its toll on the engineer trying to debug a malfunctioning logic circuit. Sometimes the problem is made even more catastrophic because the circuit may function quite well under certain conditions and fail under others. It can literally drive the design engineer up the wall! In analog and mixed signal design, whether it is a lower frequency circuit or a higher frequency circuit the causes and effects of metastability remain about the same. For those readers who may have experienced this and wish to investigate further, please review the paper on metastability in the "Engineer's Corner" in the Signal Processing Group Inc., website located at http://www.signalpro.biz.