[Coco] OT: 63B09

[gene heskett]

On Saturday, October 29, 2011 06:09:27 PM Louis Ciotti did opine:

> The processor is not for the COCO.  I am debugging a radio
> controller that has a 63B09P in it.  I found a ?NTE6809 which has
> the exact same  Pinout, but the crystal does not oscillate when I
> insert it into the MCU socket, but The old one does.  I am
> wondering if this means the NTE6809 is DOA.  It was NOS in the bag
> when I got it.  
> 
> I need to know if the problem is a compatibility issue between the
> NTE6809 and the HD63B09P or is it just that the NTE6809 is bad.
 
Well, an ordinary 6809 is rated I believe a PMOS tehcnology version rated 
for a 1 Mhz clock, the B version, which your about 10 years newer Hitachi 
CMOS is, is rated at 2Mhz.  I have a C version, rated at 3Mhz in my coco, 
and from the waveforms I can read external to the chip, I get the 
impression it could run quite a bit faster than 3Mhz.

> I don't have any persoal experience with MCUs of this vintage, and since
> the COCO uses a similar MCU I thought I would ask here.

Similar yes, compatibility may be another horse.  In this case I would look 
at the crystal and the schematic, or put the original chip back in since 
you said the clock runs with it, and measure the speed of the clock being 
applied on both the E-Clock and Q-clock pins to see what its operating 
frequency is.  Most modern test o'scopes can do this with sufficient 
accuracy for this, my 20 year old Hitachi V1065 can do it nicely. If its 
over say 1.5Mhz, then the NTE chip might not be fast enough.  Also, the 
Hitachi chip, being a CMOS design, runs its logic levels from ground to the 
logics 5 volt supply rail.  This generally works well in the coco with its 
mostly TTL circuitry, but put the PMOS chip in and the logic one voltage 
_could_ be too low (possibly below 3 volts for a logic 1) to properly drive 
what may be CMOS logic around it.

Note that neither of these chips is an 'E' version, so the clocking is 
different and not as in the coco designs.  That also means I'm not at all 
familiar either.  But when switching from a CMOS chip to a PMOS, where the 
oscillator is built into the mpu, the external circuitry is pretty 
critical, and it may not work with the 5 to 50x heavier loading the PMOS 
chip presents to the crystal.
 
> Sent from my Palm Pre on AT&T

That explains why all the html markup stuff in an otherwise text message.  
Can that not be turned off?

Cheers, Gene
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