9 Aug
1999
9 Aug
'99
5:36 a.m.
The supply connections on the schematic are +24, +12 , +5, Gnd, and -12.
The +24 is shown with a separate return from that of the other supplies. It
seems to me that there is a considerable tolerance on the +24, but that's a
common supply voltage. The thermal printer appears to be a TI EPN-9120,
which might be just as happy with 18 volts, but might require a different
set of passives at that voltage. I doubt you'll hurt anything with a
voltage as low as 18Vdc, though the stepper may want more. When I used this
mechanism, I usually AC-coupled the stepper so the circuitry didn't heat
when the printer was idle.
All indications are that the AIM uses a couple of parallel port bits to
provide the ultra-slow (110 bps) interface to the TTY via some transistors
and TTL gates. It's not the usual isolated 20mA interface. However, TXD is
on J1/pin U and its return is on S, while the RXD from the TTY KEYBOARD and
its return are on J1, pins T and R, respectively.
If you want to improve anything at all, I'd start by combining the input
clock with the R/nW signal to create the write strobe to the RAM memories.
That will provide considerably better hold time, which 2114's definitely
require. I normally 'NAND' the Phase-0 and Phase-2 clocks with inverted
R/nW to accomplish this.
There's a single-step switch and a reset switch, as well as the one that
selects the TTY keyboard.
I wouldn't be afraid to "play" with this one. It looks like it can handle
reasonable abuse.
Dick
-----Original Message-----
From: Hans Franke <Hans.Franke(a)mch20.sbs.de>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Monday, August 09, 1999 7:24 AM
Subject: Re: Spiffy Little Hamfest Find
and
and
to
>Geee, what a neat beast - I'm searching a
cased AIm (or an AIM
>case) for years.
>> I haven't powered it up yet since it seems to want 12 and 24
>> volts and I don't have a 24 volt supply handy.
>Wasn't it +5 and +/-12 ? It's a long time ago.
> Yes, 5 VDC and plus and minus 12 VDC. The -12 is only used for a comm
> port I think. The + 12 is used for the comm port and the printer. You CAN
> run it without the plus and minus 12 VDC but you'll lose the comm port printer. You
MUST have the 5 VDC.
Exact, the 12V are also needed for the TTY.
>> Does anyone have the pinouts for the
expansion and application
>> connectors on this little guy?
>Try Richards page - he did a good job and scanned a lot of the Manuals.
>http://highgate.comm.sfu.ca/~rcini/classiccmp/my_docs.htm
>>> Also, there's a switch that lets you switch between keyboard and
>>> tty but I see no place to connect a tty, not even a little dual
>>> inline connector or anything appropriate. Clues?
>
> I don't know. Maybe it uses the keyboard connector or the expansion
> connector. You should be able to trace the KB-TTY switch out if nothing
> else. BTW some of my boards don't have the switch. The traces are there
there's a
jumper soldered between two of them.
>There are two edge connectors - one supplys
the system (extension)
>Bus, the other offers the 'user' port, including a 20mA TTY (like
>the KIM)
> Mine say "J1 Application" and "J3 Expansion". The keybaord
connects
"J4". "J2" connects to the printer. I don't know where the comm
port is.
Have you looked at the stuff on Rich's web site yet. The manuals there
should tell where it is and how to use it.
J1 Application == 'user' port, including the com line and the TTY line
J3 Expansion == system bus
Gruss
H.
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