21 Apr
1998
21 Apr
'98
6:56 a.m.
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(a)u.washington.edu
[mailto:CLASSICCMP-owner@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