www.bbcnoun.com.ng 9/10 One of the major drawbacks to the use of asynchronous counters is that high-frequency applications are limited because of internal propagation delays What is a shift register that will accept a parallel input and can shift data left or right called? bidirectional universal A 4-variable AND-OR circuit produces a 1 at its Y output. Which combination of inputs is correct? A = 0, B = 1, C = 1, D = 0 A ripple counters speed is limited by the propagation delay of each flip-flop The output of a standard TTL NAND gate is used to pull an LED indicator LOW. The LED is in series with a 470- resistor. What is the current in the circuit when the LED is on? 7.02 Ma Why should a LED be pulled LOW from a logic gate rather than pulled HIGH? LOW-level current is larger. Why is the Schmitt trigger needed in the 60-Hz TTL-level clock pulse generator? to provide a sharp pulse waveform To operate correctly, starting a ring counter requires presetting one flip-flop and clearing all the others What happens to the parallel output word in an asynchronous binary down counter whenever a clock pulse occurs? The output word decreases by 1. What type of register would shift a complete binary number in one bit at a time and shift all the stored bits out one bit at a time? SISO