[Coco] Oscillator Circuits needed for EF68B09P 2MHZ versions I recently received

John Kent jekent at optusnet.com.au
Sun Jun 3 02:51:07 EDT 2012

Althought the link suggests the data sheet is for a EF6809P, the png 
image on the web site says EF6809E. Often the datasheet web sites get 
their data sheets mixed up. As Gene said the 6809E requires external 
clock generation which might be what you were referring to. I didn't 
want to have to register with the site to check which data sheet it was.

The 6809E need an external quadrature (90 degree phase shifted) clock, 
to generate E and Q signals which might be what you were referring to. 
Typically you use a 4 X clock and a dual JK flip flop to get the phasing 
right. The 6800 is a little different in that the clock signals are 180 
degrees out of phase and must not over lap i.e. the two phases should 
never be high at the same time.


On 3/06/2012 2:36 PM, gene heskett wrote:
> On Sunday, June 03, 2012 12:33:45 AM Computer Doc did opine:
>> Hi All,
>> I recently ordered a couple of EF68B09P chips thinking their pinouts
>> were the same as Motorola's MC68B09P chips.  I just downloaded the
>> datasheet for it and they are very different, almost like their version
>> of the 2MHZ 6809 used some of the original 6800 clock circuit
>> specifications. Look at the pin labels.  They remind me of the 6800's
>> pin labels.  What do you think? The following link is the one I used to
>> get the datasheet:
> The chip used in the coco's would be the MC6809EP, where the E means
> external clock generation, and of course the P means the epoxyB plastic
> case
>> http://www.datasheetdirect.com/part/EF68B09P.html
>> As you can see on page 13 (as Adobe reader counts it) and page 1-162 (as
>> it is printed in the PDF file, the clock circuit is quite complicated.
>> Does anyone have a much simpler clock circuit using a 2 lead 8MHZ
>> crystal or 4 pin 8MHZ Oscillator (metal case)?  Thanks guys in advance
>> for your input. You all are always forthcoming with information.  I
>> appreciate it.
>> Kip
>> Cheers, Gene


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