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Buses in CPU One Byte

  1. Mar 3, 2017 #1
    In a CPU there are eight wires (buses) connected to the register components.
    which means the data can travel 8 bits as a time ? if the register is 32 bit and the value i want to store in a specific register the data must be travel 4 times in a row and store the binary value to a register?
  2. jcsd
  3. Mar 3, 2017 #2
    If the wires really represents one bit, then yes.
    However, I've never heard of such weird CPU architecture where 32 bit registers had only 8 bit internal buses. Could you please give more details?

    Alternative is, that actually it's a 64 bit CPU where the 'wires' would represent a byte. Then to transfer 32 bit would require just one cycle of 'half-bus'.
  4. Mar 3, 2017 #3
    OK it's just a simple 8 bit CPU. Kind of like part of the good old 6502 (with some differences).
    There is no 32 bit register: those are four independent 8 bit registers. Let's name them R0 to R3. There is one more 'accumulator' register providing one input for the 8 bit ALU, and also there is one 'result' register for the output of the ALU.

    The ALU requires two input byte. One is provided by the accumulator, which you have to load with the data you want to use: one is provided by the register block.
    All the addressing and such is missing.

    What's now happening on the picture is that according to the 'instruction' the control unit sets the ALU to do something between the content of the accumulator and R0.
    The result available from the 'result' register.
  5. Mar 3, 2017 #4
    You mean "Instruction Address Register" & "Memory Address Register" ?
    Apart from those what else is missing ? Can i follow this diagram to learn ?
    Last edited: Mar 3, 2017
  6. Mar 3, 2017 #5
    Can't tell: compared to a 6502-like architecture there is only a few things missing (also, there are a few extra): compared to a 8085 or Z80, many things are missing or connected the wrong way.
    It would be good to know if there was a specific CPU family for the diagram or it's just a sketch.

    For 6502 reference you can check here. Apart from the explanation and some sequences there is also a data path there.
  7. Mar 3, 2017 #6
    I want to learn more briefly. Is thee any book you can suggest me which might be good fit for me.
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