# 8 to 1 MUX w/ two 4 to 1 MUX and one 2 to 4 BIN/DEC decoder

• whoareyou
In summary: You could use a single input to the 2:4 decoder and tie off the other input. Use the one input as a High/Low MUX select line, which generates two OE~ signals at the output of the 2:4 decoder...In summary, the problem statement is incorrect and the schematic is not correct.
whoareyou

## Homework Statement

Draw a diagram to show how to implement a 8 to 1 multiplexer with two 4 to 1 multiplexers and a 2 to 4 binary to decimal decoder.

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## The Attempt at a Solution

I know that I'm going to need another select line (S2) since an 8 to 3 multiplexer has 3 select lines but I've been struggling with the decoder. I have no idea what purpose the decoder should serve. Any help would be appreciated :).

whoareyou said:

## Homework Statement

Draw a diagram to show how to implement a 8 to 1 multiplexer with two 4 to 1 multiplexers and a 2 to 4 binary to decimal decoder.

/

## The Attempt at a Solution

I know that I'm going to need another select line (S2) since an 8 to 3 multiplexer has 3 select lines but I've been struggling with the decoder. I have no idea what purpose the decoder should serve. Any help would be appreciated :).

What is a "2 to 4 binary to decimal decoder"? Is that a typo? 2 binary bits to a 4-bit decimal representation? Can you post a schematic of the logic arrangement of this decoder?

berkeman said:
2 binary bits to a 4-bit decimal representation?

Yes, exactly!

Like this, except with 2 inputs and 4 outputs, and I guess we could also assume positive logic (so no inverters on the output side). The decoder could also have a chip select / enable line but I'm still not seeing how to implement it.

What you are describing is a 2:4 DeMux, which has nothing to do with decimal. Are you sure you have the problem statement correct?

Umm, no. A demultiplexer is the opposite of a multiplexer. A decoder is just like the picture I attached above. For example, if all the inputs are high except A2 then in binary that's 11 so pin 11 on the output side would be high (ie. without those inverters on the chip in the picture above.) This decoder has no select lines, but a demxer would.

whoareyou said:
Umm, no. A demultiplexer is the opposite of a multiplexer. A decoder is just like the picture I attached above. For example, if all the inputs are high except A2 then in binary that's 11 so pin 11 on the output side would be high (ie. without those inverters on the chip in the picture above.) This decoder has no select lines, but a demxer would.

Ah, I guess you're right. It's a decoder function, not a demux (routing) function.

Still, there is no "decimal" component to the decode function, which makes me wonder if the problem statement is correct...

You could think of it as a regular decoder then, 2 inputs and 4 outputs. I guess the "binary to decimal" thing is just a way for us to understand how the decoder works.

Do the 4:1 MUX chips have output enables?

They could, yeah. So the decoder would control whether or not the multiplexer is enabled? I tried thinking about that but then the decoder has 4 outputs but there are only be 2 enables (1 for each multiplexer) ...

whoareyou said:
They could, yeah. So the decoder would control whether or not the multiplexer is enabled? I tried thinking about that but then the decoder has 4 outputs but there are only be 2 enables (1 for each multiplexer) ...

Think about using only one input to the 2:4 decoder and tie off the other input. Use the one input as a High/Low MUX select line, which generates two OE~ signals at the output of the 2:4 decoder...

## What is a 8 to 1 MUX?

A 8 to 1 MUX (multiplexer) is a digital logic circuit that selects one of 8 input signals and passes it to the output based on the control input.

## How does a 8 to 1 MUX work?

A 8 to 1 MUX has 8 input lines, 3 control lines, and 1 output line. The control lines determine which input line is passed to the output line. Each control line represents a binary number where the number of digits corresponds to the number of inputs. The combination of control input signals determines which input is selected.

## What is the purpose of having two 4 to 1 MUX and one 2 to 4 BIN/DEC decoder in a 8 to 1 MUX circuit?

The two 4 to 1 MUX and one 2 to 4 BIN/DEC decoder are used to reduce the complexity of the circuit. They help in selecting the appropriate control input signals for the 8 to 1 MUX, making the overall circuit more efficient.

## What are the advantages of using a 8 to 1 MUX w/ two 4 to 1 MUX and one 2 to 4 BIN/DEC decoder?

The main advantage of using this type of circuit is that it reduces the number of control input signals required for the 8 to 1 MUX. This results in a simpler and more efficient circuit design. It also allows for easier expansion of the circuit if more inputs are needed in the future.

## What are some practical applications of a 8 to 1 MUX w/ two 4 to 1 MUX and one 2 to 4 BIN/DEC decoder?

This type of circuit is commonly used in digital systems for signal selection and routing, such as in data multiplexing, address decoding, and input/output selection. It is also used in memory modules, data storage devices, and communication systems.

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