NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

OLD News #1

Terminators for Silicon Explorer

In a recent review of a flight design using SX-A devices for prototype (and SX-S devices for flight), it was found that the connections for the diagnostic probe did not have series terminations. This does not affect operation of the flight device. However, the diagnostic probe may give errors when troubleshooting; this is NOT the time when you want your test equipment giving you more errors to troubleshoot.

Of course, the requirement for series terminations was not obvious, as previous generations of Actel devices did not require series terminations. Making it less obvious, the data sheet doesn't mention in the text¹ that series terminations should be put on the board; the supplied figures neglects them also. So this is an easy one to miss with the requirement for the flight board buried in the Silicon Explorer operating manual. We've seen this before and I'll be sending in a note to the Actelians to update their data sheet.

Here's an application note that I wrote:

silicon_explorer_terminations.htm

Cheers,

-- rk

¹ I just checked the data sheet again and looked in the obvious places and couldn't find it.

In my new OLD (Office of Logic Design) position, I am now making some of my informal e-mail lists semi-formal. These mailings will have pointers to tech tips that can [hopefully] proactively prevent errors from getting into flight designs or make things go faster and smoother. I have included an array of people from a number of organizations; different NASA Centers, ESA, etc., as you all may distribute to people in your own organizations. Please let me know if you are on this list in error or if someone should be added to it. This list is targeted towards those that either will design or review flight digital electronics.  [Note for this web-based release: to become a recipient on this mailing list, please send e-mail to: richard.b.katz@nasa.gov.

All application notes are uploaded onto my www site. New additions are noted on the what's new page. I will give these mailings from time to time; too much and they will be filtered and ignored - too little and not enough information flows. So I'll try and hit a good balance.

whats_new.htm

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