Re: [SystemSafety] Critical Design Checklist

From: Sean M. Beatty < >
Date: Tue, 27 Aug 2013 17:12:25 -0400


Here is a list of a dozen potential problems in real-time embedded systems software, many of which aren't caught by traditional testing methods. Perhaps this will be useful to you, even though it's a very specific domain. Of course, these problems are only safety-critical if they could result in triggering a hazard ..  

  1. Mathematical operations, especially fixed point (scaled integers)
  2. How are expected errors handled?
  3. Does the Risk Analysis or FMEA identify other potential errors, which aren't handled?
  4. Hardware Interfaces

. Initialization

. Noise on sensor (and other) inputs

. Power up and power down behavior

. Power usage (sleep) modes

. Watchdog timer

. ADC and DAC turn-on delays

. EEPROM interface

5. Resource Usage (RAM, ROM, and EEPROM must also be adequately sized)

. Adequate stack for worst case

. Intermediate data

. Data shared between Interrupt Service Routines and application

. Data shared between tasks of different priorities

6. Any possibility of deadlock

7. Schedulability of all tasks

8. Maximum task response times

9. Other task timing constraints (jitter, end-to-end requirements)

  1. Non-deterministic structures
  2. Task precedence constraints
  3. Uncontrolled priority inversion

Hope this helps!  


Sean M. Beatty


High Impact Services, Inc. 317-774-9895

23 S. 8th Street, Suite 100 Fax: 317-219-0437

Noblesville, IN 46060      

From: systemsafety-bounces_at_xxxxxx [mailto:systemsafety-bounces_at_xxxxxx Driscoll, Kevin R
Sent: Monday, August 26, 2013 4:38 PM
To: systemsafety_at_xxxxxx Subject: [SystemSafety] Critical Design Checklist  

For NASA, we are creating a Critical Design Checklist:

. Objective

w Too easy to just check "yes" without doing sufficient work

w Instead, "What have you done ..."

w Prove what you have done is sufficient

. We are looking for inputs to include in this checklist

. Do you have any inputs that should be included?

w Where are the bodies buried?  

We are finishing the Checklist by next week and would like to include any good questions you may have that we have overlooked. Realizing this is an imposition on your time, I am hoping some of you would be so kind as to spend just a few minutes to send questions or even question fragments.  



I am also looking for unusual failure scenarios to add to my collection,
like those I've described in my series of "Murphy was an Optimist"
presentations (e.g.


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Received on Tue Aug 27 2013 - 23:12:44 CEST

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