8080 Trainer - more info

From: Glenn Roberts <groberts_at_mitre.org>
Date: Tue Apr 21 05:56:59 1998

you're correct tony. in the assembly listing of KEX that I posted earlier I
did the assembly using my old Heath H8 and the HDOS assembler. The H8 front
panel monitor used an octal keypad & display, and the octal thinking carried
over to the assembler package. Heath also used "split octal" in the fashion
you describe, so that

  0110100110101111B (binary)
  69af (hex)
  64657Q (octal)
  151257A (split octal)

are all equivalent. if you've never seen it before you'd swear this is a
dumb idea, but it grows on you!

- glenn


> -----Original Message-----
> From: CLASSICCMP-owner_at_u.washington.edu
> [mailto:CLASSICCMP-owner_at_u.washington.edu]On Behalf Of Tony Duell
> Sent: Friday, April 17, 1998 2:59 PM
> To: Discussion re-collecting of classic computers
> Subject: Re: 8080 Trainer - more info
>
>
> >
> > Yes it is in octal. If you noticed the keypad has numbers from
> 0 to 7 so the
> > whole system works in base 8.
>
> I'd realised the keypad working in Octal...
>
> What I was commenting on was the following.
>
> Consider this 16 bit number
>
> 0110100110101111
>
> Now, that's 69AF hex (I hope), or 064657 octal.
>
> But it's sometimes useful (particularly on 8 bit machines like the 8080
> to consider it as 2 separate 8 bit bytes.
>
> 01101001 10101111
>
> Which are (of course) 69 and AF hex. In octal they're 151 and 257 (I
> hope), and it's not obvious at a glance how they're related to 064657
>
> Some 8080 people/machines (I've not seen it done on many other
> processors) write 16 bit numbers as 2 8-bit bytes in octal. They'd write
> the above number as 151 257 and not 064657. That's what I'd assumed you
> were doing here.
>
>
> > The R key is a hardwired reset.
>
> It's labelled 'Reset' on my keypad.
>
> > and the A, B, and C keys are not used by the KEX program.
>
> The 'C' label is missing (although I'd deduced that's what it should be
> from the KEX listing). The other labels are worn, but readable
>
> > By the way this kit was also called the Mini Micro Designer
> (MMD-1) and was
> > distributed by Circuit Design, inc. for $125 in kit form.
>
> That's what mine is!. It says MMD-1 in the corner of the PCB silk-screen.
>
> > Francois
>
> -tony
>
>
Received on Tue Apr 21 1998 - 05:56:59 BST