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Homework Help: 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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    Staff: Mentor

    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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