topic/MSI Logic Circuits

Question No	Title	Type	Marks
1298.	Which statement below best describes the function of a decoder?	MCQ	5
1299.	One can safely state that the output lines for a demultiplexer are under the direct control of the:	MCQ	5
1300.	Refer to the figure given below. The logic function generator being implemented with the multiplexer in this circuit produces a constant LOW on the output. TheABCinputs are checked and appear to be pulsing; also, the 0–7 and EN inputs are checked with the scope and all appear to be at 0 V. A check with the DMM confirms that power is on. What is the problem, and what should be done to correct it?	MCQ	5
1301.	Refer to the keyboard encoder in figure (a). Sometimes when the 5 key is pressed, the system attached to the keypad does not respond. The 5 input on the 74147 is monitored with a digital storage scope while repeatedly pressing the 5 key, and the waveform in figure (b) is obtained; the P above the trace indicates the points at which the technician pressed the key. What is most likely wrong with the circuit?	MCQ	5
1302.	The BCD/DEC decoder shown in figure (a) is examined with a logic analyzer and the results are shown in the waveforms in figure (b). What, if anything, is wrong with the circuit?	MCQ	5