[Coco] Checking/Testing a 68B09P

[Joel Ewy]

I have a couple Motorola EXORciser single board computers that use the
(non-E) 6809.  They were meant to be used in a backplane system which
provides power on a 100-pin bus connector (same connector as S-100 bus
(I think) but different connections), and I got only the boards.  They
came with no firmware.  I found a Tiny BASIC w/ source for the 6809 and
modified it so that it should work with these boards, but I still need
to burn some custom bi-PROMs to configure the memory maps for the EPROMs
and static RAM chips I would like to use.  This is a very slow-motion
project at the moment.  If I do ever get it working, I could plug 6809
processors into it to test.  The socketed crystal is 4MHz,  resulting in
a 1MHz clock for the CPU, but all the other chips are also rated for
1MHz, so many of them would have to be replaced in order to actually
test a 6809 at 2MHz.  That would mean (at least) 2 6821s, a couple
6850s, and a 6840 programmable timer.  Not sure I could find all of
these in 'B' versions.  But if a 1MHz test of a 2MHz part is good
enough, this might be a possibility.  Maybe this is sufficient
motivation to get back to work on that project.

JCE

Andrew wrote:
> All:
>
> Yesterday, I picked up a set of 6809 40-pin DIP processors (from a
> local Phoenix electronic junkstore - Apache Reclamation and
> Electronics). I wondered if anyone could tell me whether they are
> worth keeping or not, plus if there was a way to test them without
> using a real CoCo?
>
> Of the lot, I have 6 pieces of HD68B09P, and one MC68B09P (I also
> found a wierd floppy drive controller chip - FDC1795 - does anyone
> know anything about this - I found a datasheet, but I am wondering if
> it could be useful for building a more modern FDC board for an Altair
> I have sitting waiting for restoration?).
>
> I found data sheets for all of these parts - so, for the 6809 pieces,
> they seem to be 1.5 MHz processors (B), plastic (P) - HD=Hitachi,
> MC=Motorola. The spec sheets seem to be for all 6809 products, and
> they say they are pin-compatible.
>
> Unfortunately, none are of the 2 MHz variety for the CoCo 3...
>
> They seem like they might make a good upgrade or replacement CPUs for
> the CoCo 2 (they may even work in a CoCo 3?) - however, I don't know
> what the condition of these chips are - they were stored on
> anti-static foam, but were contained in a large mix of "junk" parts.
> None were labeled as bad, but that doesn't mean anything.
>
> Does anyone know how I could test these to verify that they work? I
> have both a Color Computer 2 and 3, but I don't want to smoke these
> units (they are my first computers from my youth - I try to take good
> care of them).
>
> Is there any way I can build a simple perfboard test circuit that
> could tell me "likely good"/"likely bad"? The datasheets don't give a
> sample circuit (I suppose there is actually an "applications"
> datasheet or book for 6809 reference designs?). I suspect that the
> simplest test design might actually be quite involved - the 6809 is a
> microprocessor, after all, and not a microcontroller - so I can
> imagine a bit of support circuitry to be required.
>
> I am not at a point where I can do this immediately, but knowing what
> to do when I can get around to it would help.
>
> Thank you!
>
> -- Andrew L. Ayers
>    Glendale, Arizona
>
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