[Coco] Kip's Single Board Computer

[John W. Linville]

On Tue, Sep 15, 2015 at 12:06:04PM -0500, RETRO Innovations wrote:
> On 9/15/2015 11:49 AM, John W. Linville wrote:
> >On Tue, Sep 15, 2015 at 12:15:15PM -0400, RETRO Innovations wrote:
> >>    The new board, as it were (it's getting less new by the month) is Kip's
> >>    take on Searle's 6 IC 6809.  His is 8, and offers some interesting
> >>    enhancement options.
> >>
> >>    But, when I try to bring the board up, I'm struggling:
> >>
> >>      * there is no signal on Q or E.
> >>      * Nothing of interest on the crystal pins (though my Tek could be
> >>        interfering with the feedback).
> >>      * I took the CPU off the board, breadboarded with HALT and RESET
> >>        high, crystal and caps installed, and still no Q or E.  I tried a
> >>        known working 6809 from my SuperPET, and nothing.
> >>
> >>    I'm new to 6809/6309, so I am not sure where to start.  I am sure once
> >>    I get the CPU running, the rest will be quick work, but the fact that I
> >>    can't seem to get a 6809 by itself to generate Q and E bothers me and
> >>    lowers my confidence that the board is ready to be debugged.
> >>
> >>    Kip, send the man a board.  I'll buy it for him.
> >>
> >>    Jim
> >I'm fairly certain that the clock problem is caused by the lack of
> >RC circuit on the RESET^ line, as I described in my earlier note...do
> >I get a board too? :-)
> >
> >John
> Happy to buy you one.  My time is precious, and saving 2-3 hours on the
> bench is worth quite a bit at this stage in my life.
> 
> So, for the 6809 noob, is there a data sheet page I should reference for the
> correct cap/resistor values?

So, the RESET^ reference on page 6 points to Figure 7 (which is on
page 8).  There it refers to the initial low time as "tRC".

Near the bottom of the chart in Figure 1 (on page 3) it shows a maximum
value for tRC as 100mS.  Oddly, no minimum is listed.

Referring to the Simon6809 schematic, it looks like he is using an R
of 10Kohm and a C of 10uF.  That should put you right at that 100mS
"maximum", but it works fine.

Anyway, I would suggest something approaching 100mS.  Since Kip seems
to have a 2.2Kohm pull-up on RESET^, maybe a 47uF capacitor from
there to ground?  Of course, that ignores the R10 and LED path...you
may have to try some different cap values if that doesn't work...

> I remember the reset controller from my 68hc11 days.  Man, Motorola was
> picky on reset.

:-)

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.