Microcontroller Selection Questions and Answers

Answer: C

The first two are the essential reading discipline. Typical figures are not tested and not guaranteed; only the minimum and maximum columns are, which is why a design that depends on a typical value is a design that will fail somewhere in the batch.

Answer: D

Correct answer: the guaranteed operating temperature range

Temperature grade is a device-level parameter given in the electrical characteristics, not a routing question. The other three are exactly what the multiplexing table answers: whether two functions contend for the same pin, whether the debug pins can be reassigned, and which timer channels can be brought out where the layout needs them. Discovering a conflict after layout is one of the more expensive mistakes in this work.

Answer: A

The silicon is the same but the smaller package simply does not bond out every signal, so the third UART or the extra timer channels are inaccessible. Memory, speed and grade are set by the ordering code independently of the package.

Answer: B

An asynchronous link tolerates roughly two per cent of combined error across ten bit times, and an untrimmed RC oscillator can be several per cent over temperature. Some parts trim their oscillator against a USB or network reference, which changes the answer.

Answer: C

One per cent of the sixteen milliampere span is 160 microamperes, one part in a hundred, and eight bits gives one part in 256. In practice ten or twelve bits would be specified so that noise and non-linearity leave the one per cent intact.

Answer: D

Flash is a large fraction of a microcontroller's die area and therefore of its price, so paying for twenty-five times what is needed is money thrown away at any volume. Endurance and vector placement are unaffected by size.

Answer: A

Rise time into a stated load is what determines whether the waveform is still recognisable at the far end, and the datasheet gives it as a curve or a table. The current limits matter for steady loads rather than for capacitive switching.

Answer: B

One sample working at double its rating says nothing about the next ten thousand across temperature and process spread, and raising the supply beyond its own maximum compounds the problem. The whole value of a specification is that it holds for every part.

Answer: C

A part sleeping at two microamperes behind a regulator drawing fifty is a design sleeping at fifty-two, and the effort spent on the microcontroller is wasted. Low quiescent regulators, or running direct from the cell, are the answers.

Answer: D

A device rating covers handling in manufacture, not a discharge to the finished product's connector, and a transient suppressor and series resistance are what stand between the two. Every exposed connector needs that treatment whatever the part's own rating.