Z80 issue, need help NOW

Discussion in 'General Electronics Chat' started by Robin Mitchell, Mar 15, 2011.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    199
    hi everyone,

    Have not got long...Im making a z80 computer for a uni interview which is tommorow. It was working until today....

    Here are two problems..
    My EEPROM has a power supply of 5V, I checked this. Why is it that when the Z80 enables the chip the data lines are about 3.5V

    The Z80 also has a suply of 5v. Why is it that too the control pins are about 4v and not 5?

    I send the halt instruction from the eeprom (01110110) and i know that it is in the memory but the z80 does not execute the halt. (i checked the data pins and wires etc....)

    Thanks very much :D
    Robin
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
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    How about schematics ;) It could be that something is loading the CPU to much. Do you use buffers on the data and address bus
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    Just a guess here, but a lot of the logic of this era was related to TTL. TTL uses 3.4V for a logic 1, and less than 0.7V for a logic 0.
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Do you measure with a scope or DMM? Remember the signals are very dynamic
    on a CPU
     
  5. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    199
    sorry guys, fixed it XD
    My bloody fault....forgot to connect A10 from the EEPROM, twas floating :D

    All is good... Oh i dont have the schematics as they are on my other computer AND there are no buffers :p
     
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