CET 3116 Homework Quiz 7

What is the purpose of a decoder's enable inputs?

- To disable the decoder outputs so that all outputs will be inactive - To allow the decoder to respond to the inputs to activate the correct output gate

One would normally expect a 16-input multiplexer to have a minimum of:

16-input data lines and four input select lines

How many input lines would be required for a 1-of-8 decoder?

3

A 1-of16 decoder IC has ________ data input connection(s).

4

A BCD-to-decimal decoder has ________ data input lines and ________ data output lines.

4, 10

A multiplexer with three select, or address, lines can select one of ________ inputs.

8

A multiplexer/data selector is a logic circuit that:

Accepts data inputs from several lines and allows one of them at a time to pass to the output.

Decoders are normally used whenever:

An output or group of outputs is to be activated only when a specific combination of inputs occur.

A three-line-to-eight line decoder has inputs CBA where A is the LSB. The output AND gates are labeled Q0 through Q7. The output of AND gate Q4 should be active when the inputs are:

CB'A'

The primary differences between a decoder and an encoder are:

Decoders may have more than one input line active but only one output line active at any given time. Encoders will have only one input active but may have more than one output line active at any given tine.

A BCD to decimal decoder would be required to have:

Four input lines and ten output lines

The output lines for a demultiplexer are under the direct control of the:

Input data-select lines.

A demultiplexer accepts data from:

One input line and transfers it to multiple output lines.

The given figure depicts a circuit that implements a 3 variable function F(A,B,C) using a 4 to 1 Multiplexer. The truth table specify the behavior of the multiplexer. Which one of the three options given realizes the circuit?

Option 1

Internal computer registers that store data are often connected to the computer data bus lines by:

Tri-state buffers.

Usually, a decoder circuit without bubbles on the outputs has only one output HIGH while all the other outputs are LOW.

True

A certain BCD-to-decimal decoder has four input lines and 10 output lines. If four input lines are capable of 16 possible combinations and only 10 output combinations are required, why have four inputs?

With three input lines the maximum number of output combinations would be limited to eight.

What is another name used for a multiplexer?

data selector

The given figure depicts a circuit that implements a two outputs, 4 variable functions f1(a,b,c,d) and f2(a,b,c,d) using a 4 to 10 line decoder 7442 and two three input nand gates. Which functions f1 and f2 realizes the circuit?

f1(a,b,c,d)= a'b'c'd+ a'b'cd' + a'bc'd' f2(a,b,c,d)= a'bc'd'+ a'bcd + ab'c'd

The figure shows a typical circuit for a BCD to Seven Segment Decoder driving a Seven Segment Display and the diferent configuarations of the led for each character. If the inputs to the decoder are A=B=C=D=0 which outputs are high?

g' is the only output that is high.

The parallel data from a branch bank's computer terminal is to be transferred over telephone lines to the main bank's computer. You would expect to find a __________ at the transmitting end and __________ a at the receiving end.

multiplexer, demultiplexer