4.2.7 Explain the function of a given circuit.
(No teaching notes for this one.)
JSR Notes:
Really, the only thing we have to go on here is the example on page 251, and the two questions on 252. Given that this is indeed what is meant by the assessment statement, it’s a pretty good kind of a question to test many of the things from this Topic; you need to produce a truth table, a full Boolean expression, and a reduced expression.
So note, in particular, how the truth table is made: it’s backwards from the way you’ve done it before; you’re given the furthest right column, so you read off the full Boolean expression based on that. Take all of the true conditions – in the case of page 251, the 1, 3, 4 5 or 7 column, and make them 1 (be carefully, since decimal row ‘1’ is actually the second.). Then fill in the ABC columns the normal way (0000 1111, 0011 0011, 01 01 01 01), and now read off the lines.
Be sure to take a very good look at the two questions on page 252 as well; remember that besides the vague assessment statement itself, 252 and 253 are all we have to go on.