Xref: utzoo comp.lsi:400 sci.electronics:2598
Path: utzoo!mnetor!uunet!ingr!b11!xenon!kerl
From: kerl@xenon.UUCP (Dan Kerl)
Newsgroups: comp.lsi,sci.electronics
Subject: metastability in ASIC synchronizer implementations
Message-ID: <26@xenon.UUCP>
Date: 24 Mar 88 22:00:46 GMT
Organization: Intergraph Corp. Huntsville, AL
Lines: 32
Keywords: synchronizer, flipflop, metastable, gate-array, standard cell


I'm new to this group,  I apologize if I missed any previous discussion
on this topic.

I am currently involved in a design that is going to silicon. A design
issue that is currently worrying me is the implementation of flag
synchronizers that are reliable at high clock rates (around 25 Mhz). I
can't really afford package pins (and their associated propagation
delay) necessary to place these flops externally - they need to be on
the chip.

Being burned by poor metastable characteristics in the past,  I am
somewhat leary of flipflops as implemented in gate-arrays. There also
seems to be a total lack of useful information from ASIC vendors on this
subject. Apart from suggestions of multiple-ranking,  I have gotten
nothing.

I am interested in hearing about any experiences that any of you may
have had concerning metastable effects in various synchronizer designs, 

as well as any suggestions on how to handle this phenomenon in the scope
of the somewhat limited design options that the gate-array/standard-cell
methodoligy offers. Also,  I would appreciate any good references. You
can send me email if you'd like, or just post the stuff.

					Thanks!   - Dan
				
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* Daniel L. Kerl			Intergraph Corp.   M/S CR1105  *
* UUCP:  ihnp4!ingr!b11!xenon!kerl	one Madison Industrial Park    *
* PHONE: 205-772-6118			Huntsville, Alabama 35807-4201 *
************************************************************************