Clock Domain Crossing Issues

The target audience for this post is digital system design engineers; knowledge of digital design is assumed.

What are clock domains?

When they first became an issue, clock domain crossings (CDCs) were determined by the inability of static timing analysis (STA) tools to determine the timing relationship between two individual signals. To a certain extent, that’s still true. The problem is one of scale. When you only had one clock, the problem did not exist. When you had two or three clocks, the problem was manageable as a small number of exceptions. When you have dozens or hundreds of clocks, CDCs are no longer exceptions; there are just too many of them. 

Demo vs. Training: What’s the difference?

For anyone involved in supporting customers of any non-trivial commercial software product, it is very important to understand the distinction between a product demo and product training.

Ideally, demos are pre-sales and training is post-sales.

No Incumbents! (Off Topic)

We have a dysfunctional Federal government. Clogging congressional phone lines must be only a precursor to the real solution, which is this: do not vote for incumbents. If ever there was a time to heed the old truism that politicians are like diapers (they need to be changed periodically, and for much the same reason), it is now. Yet every two years, most of the voters across the country expect every other district to throw out their bastards while refusing to throw out their own. Re-election rates are obscene, and the average congresscritter seems to have little incentive to push for real change. Partisanship has ensured that districts are drawn to favor one party over the other. The sad truth is, we have the government that we deserve. That can all change if we all just once hold our nose (a little harder) and pull the lever for the other guy.

No Incumbents!

The internet has a learning curve (O.T.)

Far from being a ‘digital democracy,’ the Internet is dominated by the opinions of rich, powerful people, according to a study from the University of California, Berkeley.

You needed to fund a study to figure that out? Hey, whadya know, the internet has a learning curve! If you thought “the Internet would give the poor and disenfranchised a voice” and are disappointed that they haven’t dropped everything else in their lives to (learn how to) use it, and in the meantime, the wealthy and educated have used some of their copious spare time to take the lead, was hindsight really necessary? You didn’t see this coming? Sorry to break it to you, but a couple of decades is not enough time to create a world where money does not equal political power, no matter how revolutionary the proposed mechanism might be.

Microsoft Office 2007 help for Office 2003 folk

I don’t know about you, but I have yet to get used to the menu structure of Office 2007, so different from the familiar one in Office 2003. It has always struck me as change for its own sake, throwing off imitators like OpenOffice, and more in the service of Microsoft than of users. It would seem that someone in the Evil Empire has seen the light and offered an olive branch. You can now download a new feature that offers help in finding commands from Office 2003 in Office 2007. I don’t know how long it’s been around, but the video demo from the link was recorded in March 2010. I don’t have a copy of Office 2007 yet, so I’m have no way of trying this out for myself, but I know I’ll eventually need it, so I present the information here as much to preserve the idea for myself as to help spread the word in my own limited way.

What is defragmenting a hard drive?

There is a recommended procedure on personal computers called “defragmenting.” What follows is a layman’s description of how a hard drive works and why defragmenting is important.

Scan Chain Diagrams

A reader named Anand suggested diagrams for the scan test basics article. I’m happy to oblige.

Handguns for home defense? (O.T.)

In light of this week’s Supreme Court decision, here are a few words of advice from a former marksmanship instructor to anyone tempted to run out and buy a handgun for home defense.

LinkedIn Presentations

I have two LinkedIn tutorial presentations available, an older Basic PDF file, and a newer Advanced PPS file. Of course, at the rate LinkedIn changes things, neither of these presentations is entirely up-to-date (that would require a great deal of maintenance), but both are still useful.

More Scan Test Basics

One of the highest-traffic articles I’ve written for this blog is Scan Test Basics. It seems fitting to review that article and add a few more thoughts on this topic.