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Hardware Multiplier

Discussion in 'Electronic Design' started by Rich, Under the Affluence, Oct 26, 2005.

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  1. 4 x 4 hardware multipllier!

    OK, it ain't much, and I have no idea if it will work, except watching
    the bits all follow their little truth tables in my mental simulator ...
    I drew this in Xiilinx, but have no idea yet how to run a simulation,
    or dump it to the bitstream that could program the chip (BTW, did I
    say that a prospective client has sent me a "CPLD 95XL DEMO BOARD"?
    He sent it to me in case I got this one gig, which I think that by
    chatting him up on the telephone, I inspired him to find a better,
    cheaper faster way, and so talked myself out of a job, but as a sort
    of gratituity, I think he's going to let me keep the board. And the
    Software. :)

    Anyway, there was talk of a hardware multiplier, and I've wanted to
    do this since I grasped the concept of "barrel shifter", so I've
    drawn a schematic - the Xilinx S/W doesn't have an obvious "save
    as", so I screencapped it in PSP. The little labels on the inputs
    to the AND gates are 'multiplier(3:0)', expanded, as are the
    inputs across the top. The multiplier comes in on the left, and
    the product comes out the bottoj.

    Anybody up to callng my bluff? ;-P ;-P ;-P

  2. Mac

    Mac Guest

    Your gif was almost illegible.

    You know, you can just imply a hardware multiplier in verilog or
    VHDL, and I'm pretty sure the tool will make the inference for you.

    If you want me to test your multiplier, can you put up the design

    There is a free version of the Xilinx software (webpack), by the way,
    which will easily handle small designs like this. And there is a free
    simulator, too, which you download separately. It's Modelsim, XE (xilinx

    In fact, you could do a fair amount of design work with nothing more than

  3. Rich Grise

    Rich Grise Guest

    Sorry for that. You shouldn't really need to read the lables to
    see that it's and gates and 1-bit adders, but the top four lines
    are multiplicand(3:0), the four down the left are multiplier(4:0),
    with multiplier(0) on top, and the 8 outputs at the bottom are
    product(7:0). The labels on teh intermediate and inputs are just
    multiplier(3:0), because I didn't want to squeeze in wires - they
    just stairstep their way down.
    Oh, yeah, but that's not what I wanted to do. I wanted to see if I
    could slap one together with adders and gates. :)
    Well, I can, but I'm not very proud of them - I should have had the
    tutorial open on the side, because there's some stuff I've left out
    and some stuff I have yet to do. I was kind of jazzed at getting
    the schematic this far, because building a hardware multiplier (or
    even just drawing one) has been a dream since I heard of such a
    thing. :)
    Yeah, that's exactly what I'm using, in schematic entry mode. Like I said,
    I still have some RTFM to do to get into any more depth.
    Exactly - and the thing that prompted it is that this client sent
    me a little "Demo Board" about 2 1/2" x 4 1/2" with an XC9572 on
    it and 64 I/O header pins. :)

    So, when I get a round tuit, I'll not only simulate this thing,
    but bring the inputs out to pins, and use the LEDS for outputs,
    and actually run it!

  4. Rich, Under the Affluence wrote...
    Nope, the job is still sitting there, like an unscratched itch.
    I just haven't written up the spec and fired off the P.O. yet.
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