I find this extremely hard to believe. In order to be useful with
asynchronous inputs, flip-flops should have internal positive feedback
(dynamic ones usually don't). Then the probability of metastability
decreases exponentially with time, measured in time constant units. If
I recall correctly, this time constant is the reciprocal of the
flip-flop's gain bandwidth product, or in other words the feedback
loop delay divided by the open-loop gain. The time constant is
probably a few picoseconds in state-of-the-art CMOS.
When you connect two flip-flops after each other, and only use the
last output, you essentially double the available time for positive
feedback. As the relationship is exponential, this could mean an
improvement from a MTBF of once per second to once in the lifetime of
the universe. I would expect that Hamlet manuscript from those famous
apes before seeing four _seconds_ long metastability in a usable
flip-flop.
Best regards,
-- Per Torstein Roeine email: [email protected] University of Oslo phone: +47 22 85 24 52 Dept. of Informatics, Microelectronics Group fax: +47 22 85 24 01 Box 1080 Blindern, N-0316 OSLO, NORWAY**** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****