Re: BeamRaC=er® ;-) and Reloaded Boards

> maybe someone has a better idea on how to "fix" that clock

My first instinct would be to put a low-value resistor in series with 
the signal, with the resistor physically located near the IC pin which 
is the source of the signal.  No capacitor, just a resistor...  47 ohms, 
maybe, but in the range of roughly 22 to 100 ohms.

I'm not familiar with your project, so this is general advice I'm 
offering.  But I suspect you'll find it effective... and it's an easy 
experiment to try!

Have fun and keep us posted!  Regards,
Jeff



On 2020-01-02 10:58, silverdr_at_wfmh.org.pl wrote:
> Hi and lots of CBM/retrocomp related fun in 2020 to all! :-)
> 
> We've got the next proto boards in Dec and we went on testing it on
> all possible combinations of boards and VICs we could put our hands
> on. Everything went fine until the Reloaded Mk-II [*]. Everything
> looked good at first but running test programs designed for imposing
> lots of activity of CPU, VASYL (the core chip on the board) and VIC
> showed some random glitches, leading eventually to a full crash. As we
> still have debug headers on this proto we wired (in VHDL :-) out a
> couple of debug signals, checking which out swhowed that we're
> occasionally getting phantom clocks, which we don't experience at all
> when using any of the CBM designed boards. This led us to believe that
> there must be something "different" with clocks the "Reloaded" board
> supplies. And – oh boy – the DOTCLOCK (the one that matters for what
> we do) certainly is different there than what I would expect it to be:
> 
> https://www.dropbox.com/s/kxuh2lkyqyqlmxa/2020-01-02_140548_reloaded_mkii.png
> 
> the ringing shots amplitude alone can exceed 2Vpp, effectively
> triggering false edge detection on occasions. Adding a small RC on the
> VICs end, both elements variable, allowed me to form the clock shape
> into something usable in the sense that no false edges appear anymore
> but - yeah - SISO:
> 
> https://www.dropbox.com/s/gnsqu3qgfnis5oc/capture_2020-01-02_145854_reloaded_mkii_rc.png
> 
> It seems to work and I could probably live with it but maybe someone
> has a better idea on how to "fix" that clock without
> deforming/attenuating it so much at the same time?
> 
> I was thinking about clipping the tops/bottoms (tops alone would
> probably do the trick) with fast diodes, maybe? Any advices?
> 
> 
> * - BTW, does anyone have Mk-I and would be willing to lend it for 
> testing?