[Coco] Checking/Testing a 68B09P

[jdaggett at gate.net]

On 1 Jul 2007 at 10:20, 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?).
> 
**************************

The HD68B09 is the same chip as an MC68B09. Just different fabrication 
facilities and companies. Correct that the HD68B09 is made by Hitachi as a 
second source. The B version is a 2MHz part. IF t he date code is significantly 
new,  say post 1986/87 time frame the MC/HD68B09 could run with a buss speed 
of about 3 MHz.

> 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.
>
***************

Pins 33 through 39 are different between the MC/HD68B09 and the 
MC/HD68B09E. The differences are significant that would require major rewireing 
of the COco motherboards to use a MC/HD68B09. 

 
> 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.
> 
***********************

Yes you could build a breadboard with a simple program in a ROM and test the 
parts. You  cou ld even build a breadboard to plug into a COco to test the parts. I 
would recommend a Coco 1 or a Coco2 that  has the MC68B09E socketed. On 
the breadboard you would need to have a crystal that is 4 times the .89MHz clock 
speed. That would wire to pins 38 and 39. Those pins on the breadboard would 
not wire to the socket on the Coco. Also pins 33, 34, 35 and 36 would not wire to 
the socket of the Coco. The rest are the same. 

james