"Implementation details" in code versus DO-178
This article discusses the degree of freedom in implementation of code versus low level requirements, for compliance with DO-178, and for DALs A, B, C.
Some people are talking about “implementation details” but they often have difficulties to know what is behind this wording and what is DO-178 compliant or not. This article does not address the complete flow of declination from high level requirements to architecture and low-level, but has the unique objective to discuss what the “implementation details” at code level means.
Example with LLR: "If input I1 is < 100 LSBs or > 500 LSBs, an error shall be sent to …" (traced to HLR: If input i1 is < 1VDC or >5VDC, an error shall be sent to …). Extract from Hw/Sw interface document: Input I1 is red from ADC, at address XXX. Possible value is between 0 and 1024 LSBs. 1 LSB = 10mVDC.
Beside are 3 different examples of code matching the DO-178 and one which is not matching.