[Coco] Kip's Single Board Computer

Tue Sep 15 14:00:08 EDT 2015

Yep, it probably will.  The beauty of the 'reset' chip is that it 
continuously monitors VCC for an out-of-range value and will put the CPU 
back in reset if it finds that.  A lot of times what causes a CPU to 
'lock up' is some dirty supply voltage that cause the something abnormal 
to show up on the data/address lines and then the CPU takes a hike to 
la-la land.  This chip is like a power supply watchdog.  It also 
conditions a reset button input because, as you probably know, 
mechanical switches can be noisy/bouncy.

Here's a photo of a more recent revision of the board that I did with 
onboard 5v regulator and a power supply barrel connector.  The 'HC11 
runs at 4 MHz bus speed, has full 16-bit external address bus, buffered 
data lines, some decoded chip selects, internal 1K SRAM, internal 
512-byte EEPROM, serial port, SPI port.  The board has all of the 
signals brought out to expansion connectors, the reset chip, a 16 MHz 
oscillator, RS232 port, power LED. socket for RTC and external EEPROM, 
27C256 EPROM socket, etc.  If anyone's interested in playing around with 
one or building it from scratch I could make up some documentation for 
it along with a basic monitor in EPROM.  I think I still have quite a 
few bare boards floating around that I would sell for cheap.  And, it's 
a tried and tested design.  As I said, I produce somewhere in the 
neighborhood of 1,000-1,500 of these and they're all still running now.

http://www.davebiz.com/HC11-new.jpg

Dave Philipsen

On , John W. Linville wrote:
> Well, that seems fine.  But I think a simple capacitor will do the 
> job... :-)
> 
> John
> 
> On Tue, Sep 15, 2015 at 12:34:59PM -0500, Dave Philipsen wrote:
>> So I just sent Jim an offer to send a couple of DS1233-10 chips.  The 
>> chip
>> basically holds a CPU in reset for 350ms after the power supply comes 
>> up and
>> is stable.  I have used probably 1,500-2,000 of these over the years 
>> in a
>> little 68HC11 board I designed about 20 years ago:
>> 
>> http://www.davebiz.com/HC11.jpg
>> 
>> You can see the DS1233-10 in the upper left corner of the board next 
>> to the
>> oscillator chip.
>> 
>> Dave
>> 
>> 
>> On , John W. Linville wrote:
>> >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.
>> 
>> --
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>> Coco at maltedmedia.com
>> https://pairlist5.pair.net/mailman/listinfo/coco
> 
> --
> John W. Linville		Someday the world will need a hero, and you
> linville at tuxdriver.com			might be all we have.  Be ready.