AIM-65 displays

From: M H Stein <>
Date: Thu Apr 18 23:09:47 2002

Sounds like a worthwhile project. Can't tell you why they used the 6520, can only
speculate, same as you, that it's intended to sit on the 6500 bus while the DL1416s
are a little more generic and might not interface directly without some additional
logic & decoding anyway and using up more address space to boot. Also, since
they brought a number of signals out to the display board that were not used, I
suppose they might have intended to provide maximum flexibility; I'd think that no
matter what signals & timing a display might require, you can generate it with the
PIA and the wiring would be there, while you might not have what you need available
on the bus without some extra glue anyway.

BTW, I've used 6821s & 6520s interchangeably as well without problems.

Not sure what you're looking for; the E & F ROMS are very well documented in the
separate monitor manual which is on R Cini's site AFAIK (and in your care package
waiting to go out), and if you wanted machine-readable source, the AIM itself should
easily be able to disassemble the ROMs & send the source out on the serial port for

I've done some hacking of the monitor; my main accomplishment was to reverse &
turn the printing upside down to allow mounting the board vertically with the tape
feeding down, some graphic stuff, and trivial stuff like autostarting the user program, etc.
I wouldn't think that the software to drive an LCD display would be very difficult; as I
recall, there are hooks and vectors in place for user I/O. Of course even as it is,
using the TTY switch the display is echoed out the serial port, but cursor movement
codes might be incompatible with an ASCII Serial display.

And I did find some extra DL1416s, although that won't help you with the unit that
doesn't have a display board


-------------Original Message--------------
Date: Wed, 17 Apr 2002 11:01:43 -0700 (PDT)
From: Ethan Dicks <>
Subject: AIM-65 displays

I am evaluating building a replacement display for the AIM-65 that does
not use the DL1416. I have several modern options - a 20x1 LCD is
cheap enough, as are more modern 4-char ASCII LED displays. The interface
is somewhat trivial - the connector on the AIM-65 mainboard has enough
signals to talk to a 6520 PIA (since that's what is on the normal display
board to begin with). There are couple of angles to pursue...

I have successfully tested a Motorola 6821 in place of the Rockwell 6520
in a real AIM-65. Since I have a few 6520s and many 6821s, that's a win.
Either way, it's trivial to hang a display off of the 6502 bus without
a PIA in the way. I'm curious if anyone knows why they bothered to
put a 6520 on the display card? Did they want to keep the bus loading
to a small, known quantity? If so, then I'll consider that any ASCII
LED solution I come up with needs to have appropriate signal conditioning.
I can't see how a modern LCD display would load the bus any worse than
a 6520, so it might be worth the direct approach.

So... the hardware is no big deal. The software, though, could be lots
more work. I have real ROMs and ROM images. Are there any sources to
the AIM-65 ROMs that are in a state to be compiled back into working,
matching binaries? If I'm going to change the nature of the display,
the code will have to follow. If the code is changing, then there's
no reason I can't experiment with a multi-line display - I have a 20x4
VCD and a 20X4 LCD display already in hand. I think I can locate a
40x2 in my junk box, but at first, I'll probably ignore the right half
and if I used it, treat it like a 20x2.

Is there anyone out there who has done any real AIM-65 hacking? I can
start from zero if I have to, but if there's any preexisting work out
there, I'd like to see about starting ahead of zero.

- -ethan
Received on Thu Apr 18 2002 - 23:09:47 BST

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