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  1. #1
    Member level 3
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    Dec 2004
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    Is special bus often used in 8-bit CPU system?

    We often see AHB or APB in SOC system using ARM CPU and other bus such WISHBONE is also used in some 32-bit CPU system.
    But in my design case,a 8-bit CPU(ex.8051) is enough to read/write the 8-bit control/status registers in the co-processors(maybe 3 or 4).And i want to make the co-processors access the data in the RAM directly,which is to be processed.So i am trying to design a bus to connect the CPU,the processors ,and an arbiter is also needed.But i can hardly find a 8-bit bus design in the papers.So i want to know whether my design is realizable and resonable or not? Thanks!
    As an alternative,I can connected all the control/status registers and RAM to the 8-bit CPU and map them as outside RAM.But the CPU will take over all the data transfers,which takes more time compared to using a bus.

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  2. #2

    Is special bus often used in 8-bit CPU system?

    if the processor will not connect other device designed by others, you can use any bus, of course the data is 8 bits, even you can define a bus by yourself

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  3. #3
    Full Member level 4
    Points: 3,420, Level: 13

    Join Date
    Jun 2005
    26 / 26

    Re: Is special bus often used in 8-bit CPU system?

    As u r planning for an soc, u can define a ur own particular bus which suits all ur devices, i.e 8 bitdata bus and supports 2 or 3 masters and an arbiter for these masters.
    Even though u use AHB bus u can use only 8-bit bus, There are four strobes for example for a 32 bit bus i.e
    0-7 bits, 0001
    8-15 bits, 0010
    16-23 bits, 0100
    24-31 bits,1000
    if u use 1111 then the data is 32 bits
    and also u can use HBurst and HSize in the AHB protocol


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