Suppose that AB and CD are 2-bit unsigned binary numbers
(a) Find the truth table for the function F with 4 inputs A, B, C, D to satisfy the following condition
if AB>= CD, then F = 1, otherwise F = 0 enter image description here
(b) implement 8x1 multiplexer using 3x8 decoder and 3-state buffers
Am I right?
-
1\$\begingroup\$ Isn't an 8x1 multimplexer supposed to have 8 data inputs? \$\endgroup\$Wouter van Ooijen– Wouter van Ooijen2018年06月18日 06:03:47 +00:00Commented Jun 18, 2018 at 6:03
-
\$\begingroup\$ Yes, why......? \$\endgroup\$김태후– 김태후2018年06月18日 06:33:30 +00:00Commented Jun 18, 2018 at 6:33
-
\$\begingroup\$ The drawing after (b) seems to answer subquestion (a), not (b). \$\endgroup\$Wouter van Ooijen– Wouter van Ooijen2018年06月18日 06:35:10 +00:00Commented Jun 18, 2018 at 6:35
-
\$\begingroup\$ Thank you.. I've seen next (c) Design the logic diagram for the truth table of (a) using the circuit of (b). this is that.. \$\endgroup\$김태후– 김태후2018年06月18日 07:00:46 +00:00Commented Jun 18, 2018 at 7:00
-
\$\begingroup\$ The output OR gate is not needed, only one gate is active , the outputs must be connected together \$\endgroup\$Dorian– Dorian2018年06月18日 12:27:05 +00:00Commented Jun 18, 2018 at 12:27
2 Answers 2
a) You are wrong. Your truth table has several wrong entries, e.g. 0001 should be 0, not 1.
b) The drawn in OR gate though is wrong. With all but one input floating it is anyones guess what the output of an OR gate would be. Simply connect all the outputs together without further logic.
c) Your idea of connecting 1 and NOT D input signals to the 3-state buffers though is right. Except your bad truth table makes the result wrong. You also need 0 input for some.
a. The truth table for a part is wrong. A in case of 0010, F should be 0 not 1. Please correct the truth table.
b. Since the truth table is wrong, the given answer for this part is also incorrect. However, the idea of putting together the circuit is correct, just eliminate the or gate at output as only one of the tri-state buffer will be active at a time and rest outputs are in high impedance state. You will also need to connect some inputs to 0 and D as well.
All the best