[Premium-Rx] Following up my post of yesterday on the RF-590 A17 Remote Control Interface - From Jim Sorenson

[Jim Sorenson]

Thanks to all who responded with information and documentation concerning
the RF-590 Remote Control Interface.

I was taken down a peg by a couple of members who told me that I could not
possibly be referring to "EBCDIC" on firmware associated with the RF-590,
implying that somehow I must have mistakenly tried to interface an ancient
punch card or paper tape reader with my unit. What I probably should have
said was binary coded decimal (BCD), which is what EBCDIC is based on. I let
myself open.  The RF-590, does in fact, however, use BCD to control the
RF-551A preselector, which even Harris will admit to in their RF-551 doc.

I cannot find the post in either the archives or on my machine, but I
thought I recall someone in group mentioning that the A17 on the 590 used
BCD and the A17 on the 590A used ASCII.  I well could be mistaken about
this, however the EPROM on the A17 Remote Control Assembly in my unit is
dated 1982. That's 22 years ago and just three or four years after I had my
hands on my first computer, an Apple II Plus.  I don't know what Harris was
using for data processing in the 70s and early 80s, but I know for a fact
that IBM are still shipping the AS/400 with EBCDIC - who knows which variant
though.

What I can tell, however, is that my terminal/port data monitor appears to
be connected in serial fashion with the A17 and that the A17 expects 300
baud at 8 bits and not 7, suggesting BCD. But what do you do when there is
no conversation because one side does not know the secret word?

The physical layer is not the problem, it's the hand-shake layer that is
probably going to stop me dead in my tracks: The clues are building up, but
ultimately, without reading and understanding what was programmed into the
EPROM in the first place, chances for a solution are slim. Would anything on
it be reliably readable, and if so, would it be in anyway helpful or even
remotely understandable? I would have thought some kind of hex dump would
contain much useful information.  Given when it was designed and
manufactured, there must a trivial solution here, but remember, I'm not an
EE. I guess I'd better consult my brother (an attorney) about what trouble I
might be getting into for divulging proprietary information over the net
that I might have come across accidentally through my own experimentation?

I shall, however, continue to plow ahead.

Jim