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Microprocessor MC68000. Pls help me!

  1. Oct 25, 2007 #1
    One of my major subjects in this semester is Microprocessor, MC68000. I have a hard time with this subject. Please help me to answer certain questions:

    1)Design address decoder for following devices
    - RAM(128Kbyte) with initial address of $400000
    -ROM(32kbyte) with initial address of $000000
    -I/O with address between $800000-$80001F

    2) Write a program which satisfies the equation: y= x(square) + z
    y is a 16bit unsigned number which store in $1000
    x and z is a 8 bit unsigned number which store in $1002-$1003
  2. jcsd
  3. Oct 25, 2007 #2

    jim mcnamara

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    Do you know the instruction set for the Motorola chip? You need to know that already.

    What work have you done so far? Please you show us.
  4. Oct 26, 2007 #3
    The questios listed all are the theoritical question. We do not have to design the real circuit. For the first question, I already have the answers. But pls help me for the 2nd question.
  5. Oct 26, 2007 #4
    For the square part use a look-up table and an index to count up to x and read the table (which should contain the square of each x values). The rest is straightforward; addition.
  6. Oct 26, 2007 #5


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    the 68K has a multiply instruction. both signed and unsigned. squaring a number is trivial.
  7. Oct 26, 2007 #6
    Sorry to say that I don understand at all what's going on at the moment. I'm thinking of using multiplication before, but the requirements for it really make me confuse. Besides that, if squaring a number is trivial, then can I assume that y=z? If not, what should I do? What are $1000, $1002,$1003? Is it a memory address at address register?
  8. Oct 27, 2007 #7
    You're right. But it -depending on the numbers- takes more clock cycles than doing it with a LUT.
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