Microcontroller Selection Questions and Answers

Answer: C

Correct answer: industrial and automotive products with long production lives

A longevity programme is a commitment to supply a part for ten or fifteen years. It matters where the product will be built for a decade and where a change of microcontroller means requalification, safety recertification and possibly customer approval - costs that dwarf the part price. A consumer product refreshed annually and a one-off instrument have no such exposure.

Answer: D

The point is technical rather than commercial: a pin- and register-compatible part from another vendor, or another family, that the board and the firmware can accept. Two distributors selling the same single-sourced part gives no protection at all.

Answer: A

Wrestling a design into a part that barely fits costs engineering time and delays revenue, and the saving on a hundred thousand units may be less than the salary spent. That trade is precisely why the cheapest part is often the wrong one.

Answer: B

Weeks are lost to a debugger that cannot see a variable or a probe that drops the connection, and the cost falls on every engineer on the project. It is the criterion most often ignored in a paper comparison and most often regretted.

Answer: C

The certification requires evidence about the part's failure modes and the diagnostics that detect them, which only the vendor can supply. Parts sold for such use come with a safety manual and often with a self-test library.

Answer: D

The qualification is exactly the body of evidence an automotive customer requires, so what it covers is why it is demanded. A part without it may be electrically identical and will still not be accepted onto a vehicle programme.

Answer: A

Appliance safety standards require the controller to detect its own failures, and the library supplies tested routines that check registers, RAM, flash and the clock. Writing and certifying such tests oneself is a substantial undertaking.

Answer: B

Working on the bench at twenty degrees and failing at minus twenty is the signature of a temperature grade problem, and the oscillator and the converter are usually the first to go. The other three would fail identically at any temperature.

Answer: C

A drop-in replacement needs no board change and no driver work, which is exactly why the family was chosen. Rewriting in assembler buys perhaps a fifth at enormous cost, and changing vendor restarts the driver and toolchain work.

Answer: D

A datasheet's feature list counts functions across the whole device, and the multiplexing table is where it emerges that the second SPI shares pins with the converter inputs. Checking it takes an hour and saves a board respin.