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help me to make a ic tester using 8085 microprocessor

Discussion in 'General Electronics Discussion' started by jayadratha, Jan 6, 2012.

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  1. jayadratha

    jayadratha

    10
    0
    Jan 6, 2012
    I have a problem in regarding this project. that is input pin output pins are different for some ics. 7402 have 2,3 pins as input and 1 as output and in 7400 1,2 as input and 3 as output. so in runtime how can i change the circuit for input output by checking the ic number have to test? please help me, i really need your help friends.........

    and if i connect 5volt in the output of mux or demux is the ic will be damaged? please help :( :eek:
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    Essentially you're asking how to identify a 74 series logic IC.

    It's really tricky.

    In most cases the power supply pins are in predictable places, but do you wish to allow for the IC being inserted incorrectly?

    Also how do you intend to detect how many pins the device has?

    The easiest way to go about this (once you've determined the power supply pins) is to apply a weak pull up on each pin. This is safe because the resistance is high, and it can be really weak because TTL will float high if left disconnected.

    If any pin is still low, it's clearly an output.

    You can then go from pin to pin pulling each pin (weakly) low. If it stays high, its an output. If any other pin changes state then it's clearly an input and those other pins are clearly outputs.

    You may have difficulty with pins that can be either inputs or outputs, or which are tri-state.

    Once you've determined which pins are definitely inputs and outputs (it will be a subset of the pins) then you can compare this to all known 74 series ICs, dismissing any that are obviously incorrect.

    Then it is a case of trying to determine from the list of what remains, which chip you have.

    Then, presumably, you go ahead and test the functionality completely.

    It's a non-trivial project.
     
  3. jayadratha

    jayadratha

    10
    0
    Jan 6, 2012
    actually i can't understand what to do. in all 14pin ics input and output pin numbers are not same. so if i make the circuit for a ic then how i can change dynamically in runtime for other ic? Actually i want a general circuit in which if microprocessor send 8bits then those 8bits will go to the desired input pins of the ic. In all ic the input pins are not same, and thats the problem. :(
     
  4. jayadratha

    jayadratha

    10
    0
    Jan 6, 2012
    actually i can't understand what to do. in all 14pin ics input and output pin numbers are not same. so if i make the circuit for a ic then how i can change dynamically in runtime for other ic? Actually i want a general circuit in which if microprocessor send 8bits then those 8bits will go to the desired input pins only of the ic. In all ic the input pins are not same, and thats the problem. Please help me friends..............:)
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    Don't start multiple threads for the same question. It annoys the moderators
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    The simple answer is to use a newer uC that has at least 14 I/O pins and connect one to each pin of the IC under test.

    You just change the pin functions from input to output as required.
     
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