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I'm looking for a flowchart explanation of how both of these 32-adder Multiplication hardware pieces work:

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The other:

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An example of how the flowchart could describe the hardware is seen here:

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I'd honestly just like the flowchart so I have a better understanding of what's going on.

Best, and thank you!

Dan
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  • What exactly are you trying to do? – Evan Carslake Apr 16 '15 at 20:47
  • There is no sequential control in the schematics, just combinatorial logic. No flowchart applies. That said, these look like sloppy handouts, at best: the numbers don't add up. In the first diagram, it says `Product 64 bit` - with 31 single bit lines to it and explicitly marked 32 from the leftmost "ALU". (Providing "0"-inputs to ALUs but the least significant one is a bonus - from the very same oversight/misconception.) The second one is a real turn-off, adding 32-bit values _of different significance_ in "32-bit ALU"s, never bothering with carries from less significant partial products. – greybeard Apr 18 '15 at 07:02

1 Answers1

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Out of the first two diagrams, only the first seems to be partially correct. I've seen the second diagram in Computer-Organization-Design, and for me it is not correct as well (or atleast I can't decipher that :-)).

So let me try to explain only the first diagram

Mcand = Multiplicand register

Mplier0 = 0th bit of the Multiplier register (lsb)

Mplier1 = 1st bit of the Multiplier register

Mplier31 = 31st bit of the Multiplier register (msb)

Mcand.Mplier1 is performing logical "AND" operation Multiplicand and Multiplier first bit. e.g. if Mcand is 1101 and Mplier1 is 1 the result is 1101, and if Mplier1 is 0, the result is 0000

Now the top-right most ALU has two inputs

  • Left input: Mcand.Mplier1 a 32 bit value, as explained above.
  • Right input's 32 bit value is made by, 31st bit is zero as shown. And rest of the 30 bits are most signficant bits of Mcand.Mplier0 except the 0th bit. 0th bit goes directly to set Product0 bit (i.e. 0th bit of the Product register)

Now the ALU at the second layer (or row), has two inputs as well.

  • Left input: Mcand.Mplier2 a 32 bit value, as explained above.
  • Right input's 31st bit has to be the "carry out" of the first ALU, the diagram sets it to zero, which seems to be incorrect. Rest of the 31 bits are set from most significant 31 bits of the output of first ALU. The remaining 0th bit output of first ALU goes directly to set Product1 bit.

This is repeated for the remaining 30 ALUs.

SwiftArchitect
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Ruwan Janapriya
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