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_at_mch20.sbs.de>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Monday, August 09, 1999 7:24 AM
Subject: Re: Spiffy Little Hamfest Find
>
>>>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
and
>> 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
and
>> 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
to
>> "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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>HRK
Received on Mon Aug 09 1999 - 09:36:19 BST