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5188Re: Address Displays

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  • Al W,
    Mar 6 9:30 AM
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      Nathan,

      An address display will be a big help when you are entering data or
      looking at various memory locations but one thing that you need to
      consider is that the address won't always be correct when you stop a
      RUNNING program to look at the display.

      The reason is the address buss is used for various data transfer
      operations by the 1802 chip internally and most 1802 designs don't have
      a synchronized halt process. Somtimes you stop at the right time and
      sometimes you don't. You can decode the various states and cause the
      address bytes to always reflect the proper data but that adds a little
      to the complexity.

      One of my 1802's has individual led's on the address buss and when the
      ubiquituous binary counter program is running you can see the upper
      address bits changing in time with the data bits. Guess how the D
      register gets transferred to the output data buss!

      My 1802 also is timed for a synchronous halt so that one can step
      through a program exactly one whole instruction at a time but I never
      use that feature. Guess I shouldn't have wasted time designing it in.

      Al Winfrey
      ....



      --- In cosmacelf@yahoogroups.com, rileym65 <no_reply@...> wrote:
      >
      > If you are looking for a circuit for it, take a look at the Micro/Elf
      > schematic on my site (http://www.elf-emulation.com/) That will give
      > you an idea how to hookup TIL311s for address display.
      > Mike
      >
      > --- In cosmacelf@yahoogroups.com, "supertrone_1999" <supertrone@>
      > wrote:
      > >
      > > Hello Group,
      > > I have pretty much the standard ELF and I'd really like to add
      > > address displays to it. Anybody got any advise on this?
      > > Nathan Trone
      > >
      >
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