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« DO-178B Gyan | Main | Selecting Aerospace Software Supplier - view from the other side »

July 31, 2007


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Fadi Mhanna

Fantastic blog you have going here. Thank you for all the information.


It is a most interesting and informative blog to explore about DO178B.


Hi Amitabh,

Do you have any documents for software component testing (CTT or low level testing) and hardware / software integration (HSI) testing?



@Divya, sorry about that.
The link used to work. Or I thought it did :(
Will check up.
Meanwhile try this:;jsessionid=CAF01012B14ADBF4732918E4667C6971?doi=
I just tried and this one works. It will download directly. Meanwhile I will try and fix the original link


Hi Amitabh,

The link is not working.

can you please help.


1. You need to obtain 100% structural coverage. Period. You could do it by any one of the tests or by a combination of all. It is easier to obtain structural coverage by LLT. However, the trend is now to obtain as much structural coverage at higher levels of testing as possible; and then compete the remaining ones by LLT. I think DO-178C will recommend this.

2. You need to integrate one of the existing over the counter tools, such as, RTRT, LDRA, with HSIT. The vendors should help you do this. If you have skilled engineers you should be able to do this yourself, you need to use a debugger.


Hi Amitabh
1. Is 100 % Structural coverage(basing on the level of the software)is needed for all levels of testing i.e., HSIT,SIT,LLT? or is it ok like if i got complete 100 % coverage in SIT and i don't worry about the coverage part in LLT level or vice versa....

2. what are the normal practices for carrying out HSIT? In our company we use NI based Lab View set up for HSIT... and using this set up coverage part can't be what u suggest to achieve coverage in HSIT?

Please reply so that it will be helpful...


hi Amitabh

At section 5.2.2 d its mentioned that "Control flow and data flow should be monitored when safety related requirements dicatate for example Watch dog timers ,reasonableness checks and cross channel comparisions"

From the above statement is it mandoatory that safety system requirement to be present for watch dog timer. For our project this requirement is a derived high level requirement.
Second question is that can you please clarify what reasonableness checks exactly means?

Please reply for my above queries.



How to qualify a in-house developed verification tool as per DO-178B ? Pls help me on this...

Kirana Veerhu

Hi Amitabh,
Your posts on DO178B are good and thought provoking. Recently i have attended DO178B training and i need to face a rather tough test :) Do you have any questionaire on DO178B to make things easier for me?
Thanks in advance :)


Hi, I was browsing (Google) once again just for the actual meaning of the acronym MC/DC, not so easy to remember, and ran into one of your articles. You have an interesting blog from what I've read so far. Regards.

Chris Scutcher

I'd just like to say that reading your blog has been extraordinarily helpful for me.

I am fresh out of Uni and have begun work at a company that specialises in safety critical software.

I am currently trying to get to grips with the DO-178B and I am very thankful for you blog and the information you've got here.

So thanks a bunch!


I recommend that you start where all of us start. The NASA Technical Memorandum: A Practical Tutorial on Modified Condition / Decision Coverage (MCDC).
Here is the link:
If this does not help you may send me (either on this blog or to my e-mail id) the cases you are struggling with, and I shall be glad to help.

Veena Shankari

whenever i browse for DO178B information..I bump up into this website.

I need an help with respect to MCDC .
I really find it difficult to select text cases if number of variables is more than 3.

Can u kindly help me posting some basic of MCDC.I have not worked in any Level A softwares .

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