An Engineer's Literary Notebook

Exploring the real and surreal connections between poetry and engineering

Of Contentment and Metastability

Posted by xbanguyen on August 5, 2009

There is probably an interesting lesson in etymology explaining the origin of the words contentment and contention.   Contentment is a state of mind that follows the ebullient feeling one gets after figuring out that signal contention due to the asymmetrical rise and fall times  of an inverter is the cause of a failed data transfer.   Such are the moments  that make engineering an appealing profession.  There is an underlying sense of optimism in our line of work because we believe that for every engineering problem there is at least one solution.  We’ll keep looking until it’s found.  And somewhere along the way, if we shift our perspectives just a little when letting our left brains rest, we’ll also find that certain technical words carry their own kind of charm.

Consider clock domain crossing.   The word domain and demesne share the same Latin root.  I like them both, but that is the subject of another post. The idea that we can create multiple domains of time holds a certain attraction (because it gives us an illusion of being in control, to have dominion, over time?)   Nevertheless we don’t take clock domain crossing lightly because just like any time we transcend a boundary, there are dangers. In this case it is metastability.  Technical cautions aside, there are such opposing forces in a single word, metastability, that give it a certain cachet.  The bipolar nature of digital signals is such that signals that fall within that forbidden window will oscillate, not at all a desirable state of being.  So just like the “watch out for the baobabs”  warning reiterated by the pilot who befriended the Little Prince in the Sahara, I would like to reiterate a similar warning to the young engineering students to watch out for unsynchronized signals when crossing clock domains.  And yes, just like it is easy to pull out the seedling baobabs from the tiny planet, it is easy to add a couple of flip flops to prevent the potential disaster.

Speaking of opposing forces, they can be found in this stanza of a favorite poem by Dylan Thomas, a fitting way to end this post.


The force that through the green fuse drives the flower
Drives my green age; that blasts the roots of trees
Is my destroyer.
And I am dumb to tell the crooked rose
My youth is bent by the same wintry fever.

The force that through the green fuse drives the flower
Drives my green age; that blasts the roots of trees
Is my destroyer.
And I am dumb to tell the crooked rose
My youth is bent by the same wintry fever.


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