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Sunday, February 26, 2012

Difference between MAX and MIN mode


Maximum mode
Minimum Mode
When MN/MX(bar) low 8086 is in maximum mode.
When MN/MX(bar) high 8086 is in minimum mode.
In maximum mode 8086 generates QS1,QS0,S0(bar),S1(bar),S2(bar), LOCK(bar),RQ(bar)/GT1,RQ(bar)/GT0 control signals.
In minimum mode 8086 generates INTA(bar), ALE, DEN(bar), DT/R(bar), M/IO(bar), HLDA,HOLD and WR(bar) control signals.
So clearly there are multiple processors in the system.
There is only one processor in the system minimum mode.
Whereas in maximum mode interfacing, master/slave and multiplexing and several such control signals are required

In maximum mode a bus controller is required to produce control signals. This bus controller produces MEMRDC, MEMWRC, IORDC, IOWRC, ALE, DEN, DT/R control signals.
In minimum mode no interfacing or master/slave signals is required.


In minimum mode direct RD WR signals can be used. No bus controller required. A simple demultiplexer would do the job. of producing the control signals. This demultiplexer produces MEMRD, MEMWR, IORD, IOWR control signals.
Maximum mode 8086 system

Minimum mode 8086 System

14 comments:

  1. third point is wrong......
    there is single processor in mim mode....
    while multiple processor in max mode...

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    Replies
    1. Thank you Diya for pointing out the errors. So i have updated the post with correct points an some more points. Thank you again.

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  2. thanks, it is some useful information

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    Replies
    1. you are welcome... keep visiting....

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  3. Aren't ALE,DEN,DTR found in min mode?

    This point is confusing:


    This bus controller produces MEMRDC, MEMWRC, IORDC, IOWRC, ALE, DEN, DT/R control signals.

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  4. why is there bar over certain pins in 8086? What does tat indicate? please help

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    Replies
    1. Bar indicates active low signals.
      These signals will be 'ON' on input 0 bit and 'OFF' on input 1bit.

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    2. Bar indicates active low signals.
      These signals will be 'ON' on input 0 bit and 'OFF' on input 1bit.

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    3. Thank you Akansha. Do that mean MX (bar) indicates MAX mode is applicable only when the input bit is 0? If so, what will happen at pin 26 or pin 29 when the input is 1?

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    4. For some signals to get output without any delay we try to give ACTIVE LOW signals.So,if you find any BAR on any pin of mp/mc then it means tgat it is ACTIVE LOW...

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    5. For some signals to get output without any delay we try to give ACTIVE LOW signals.So,if you find any BAR on any pin of mp/mc then it means tgat it is ACTIVE LOW...

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  5. The diag is taken from which text book

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    Replies
    1. Advanced Microprocessors and Peripherals by AK Ray and KM Bhurchandi.

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  6. It is noted that in minimum mode, the processor cannot be accessed by other master. So what is the importance of HOLD and HLDA pin in 8086 minimum mode configuration?

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