I am stuck on a homework problem that I have difficult time understanding:
Draw the state diagram of the circuit described below, with detailed
explanations:A detection circuit has two inputs, x1 and x2, such that an output z
will become 1 as soon as 4 consecutive input pulses are received and
the 4-bit sequence contained at least two x1 pulses. Assume the
sequences consisting x1 and x2 may not overlap.
Could anyone clarify this question for me? Does a "pulse" by definition means when an input goes from 0 to 1, then to 0? When it says "4 consecutive input pulses" does it mean for both inputs, x1 and x2? I am not getting the whole picture together…
Best Answer
The use of the word "consecutive" might be a bit confusing.
The condition means that the output goes active after four consecutive pulses, of which at least two are on x1. In other words, it doesn't simply need to see two pulses on x1, there have to be two x1 pulses in the last 4 pulses.
Thus the sequence:
X1 X2 X2 X2 X1
contains 2 X1 pulses, but not within 4 consecutive pulses, whereas
X1 X2 X2 X1 contains 2 X1 pulses within 4 consecutive pulses.