8-Bit Ripple Carry Multiplier using 4-Bit Adders

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In summary, an 8-bit multiplier can be created using 4-bit adders by connecting the outputs of each stage to the input of the next stage.
  • #1
tmlee2
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Hey Everyone,

I want to design an 8-bit Multiplier, using 4-bit Adders. I created a Ripple Carry Multiplier using 16 4-bit adders, but after debugging realized it doesn't work. I got this schematic off of a 4-bit multiplier i saw online, but can't find the link to it anymore.

Here is the schematic I created:
8546963078_894888afed_z.jpg



SUMMARY HOW IT WORKS:
Mantissa 1 (A7-A0) go into A7-A0 of each ADDER stage.
Mantissa 2 (B7-B0) go into the CI of each ADDER stage.
0’s go into the first stage of B7-B0, to initialize it.
The output of each stage (X7-X0) go into the input of next stage (B7-B0).
The results (P7-P0) are on the CO of each stage, and the outputs of the last stage (X7-X0) are P15-P8.

If someone could please help me correct it or see any mistakes or know of any another way to create an 8-bit multiplier using 4-bit adders. Thank you for your time and help!
 
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  • #2
Its in the adressing take the lower 4 bits connect to the one 4 bit adder. Take the upper 4 bits to the second adder. Have the same signal activate both Chip enable pins. you will have to connect the output of a3to a1 of the second 4bit adder. This will essentially make 2 4bit adders act as one 8bit adder. a
A0to A3 connect output a3 to A0 input of second adder. On the
second adder adress as A4 to A7

edit forgot to mention each output of the adder needs to connect to the input of the next bit.
Ao output to A1 input a1 ouptut to a2 input repeat till A7
 
Last edited:
  • #3
Thank you for your feedback, but the IC's I am using (74HC283) do not have an enable pin, so that solution won't work, I should have listed that before.

EDIT: Do you know any 4-bit adder ICs with an enable on it? That would be very helpful.
 
Last edited:
  • #4
The method I described was utilizing a flip flop circuit as an adder. The chip you described works differently. Its been sometime for me on the circuit I described I would recommend you post the datasheet for the chip you have. I am on my phone atm so would be tricky for me to do so.
However the datasheet may provide the answer you need at least it will help us with your circuit.
 
  • #5
  • #6
I have found a solution to my problem, I can do what you described above but need 2-input AND gates to drive each stage and still use my 4-bit Adder ICs. Thank you for your help!
 
  • #7
No problem glad you found the solution
 

1. What is an 8-Bit Ripple Carry Multiplier using 4-Bit Adders?

An 8-Bit Ripple Carry Multiplier using 4-Bit Adders is a digital circuit that performs multiplication of two 8-bit binary numbers using four 4-bit adders. It uses the ripple carry method, where each adder in the circuit performs addition one bit at a time, with the carry out from each adder being propagated to the next adder.

2. How does an 8-Bit Ripple Carry Multiplier using 4-Bit Adders work?

The multiplier works by breaking down the multiplication operation into a series of additions. Each adder takes two bits from the multiplicand and multiplier, along with the carry in from the previous adder, and produces a sum and a carry out. The carry out is then fed into the next adder, creating a ripple effect until all the bits have been processed.

3. What are the advantages of using 4-Bit Adders in an 8-Bit Ripple Carry Multiplier?

Using 4-bit adders allows for a more efficient use of resources, as 4-bit adders are smaller and require fewer logic gates compared to an 8-bit adder. This results in a smaller circuit and faster processing time. Additionally, using multiple 4-bit adders allows for a modular design, making it easier to test and troubleshoot the circuit.

4. What are the limitations of an 8-Bit Ripple Carry Multiplier using 4-Bit Adders?

One limitation is that the ripple carry method used in this multiplier can result in longer processing times compared to other multiplication methods, such as carry-save or Wallace tree. Additionally, as the multiplier only uses 4-bit adders, it can only handle 4-bit operations at a time, making it less efficient for larger numbers.

5. What are some potential applications of an 8-Bit Ripple Carry Multiplier using 4-Bit Adders?

This type of multiplier is commonly used in digital signal processing applications, such as in microcontrollers or digital signal processors, where speed is not a critical factor. It can also be used in other applications that require multiplication of smaller binary numbers, such as in cryptographic algorithms or error-correcting codes.

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