ISTR that Marlin P. Jones & Associates had a 4x40 character LCD module pretty
reasonably priced. If you simply map it into the space the 6520 would occupy,
you may have satisfactory results. I know for starters you'll be ignoring
half of 4 lines instead of half of two, but once you hack the AIM monitor to
handle the LCD, you'll be better off with the bigger display. ISTR that
there's an AIM65-version that has 40-character display lines. You may be able
to get a copy of the ROM listing for that. You'd then only have to deal with
addressing into the LCD, and the native firmware would handle the other
details for you. My AIMs haven't got a 40 character display, so I can't help
you with the ROM listing, though.
The 6520 doesn't apply a major load, but it is a really silly thing to use
under any circumstances. The mfg sold 'em though, so they had to use 'em for
something. You could pretty easily attach a 6520 between the LCD and the
bus. The LCD probably can't drive the bus, however, with all its capacitance,
so I'd look long and hard at the use of a 74HC245 for the data bus buffer if I
were looking to attach it directly, which seems to me to be a good idea.
Attach phase-2 to 'E' and R/W to R/W. Then attach A0 to RS. Use the '245
"backwards, i.e. with the bus attached to the high-numbered pins, so that you
can attach R/W to the A*/B signal to steer the data and the 6520's CS2* signal
to enable the datapath.
I'll have a look to see whether I have any ROM listings. I thought I did,
but, well ... they say the mind's the second thing to go ... can't remember
the first ...
regards,
Dick
----- Original Message -----
From: "Ethan Dicks" <erd_6502_at_yahoo.com>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, April 17, 2002 12:01 PM
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 use 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
>
>
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Received on Wed Apr 17 2002 - 18:40:29 BST