Jeff Epler wrote: > On Tue, Aug 26, 2008 at 12:08:10PM -0500, Jon Elson wrote: > >>I'd be willing to bet a meal at the next Workshop that this is >>either a crosstalk or reflection problem on whatever signal is >>used to clock the config data into the FPGA. [...] > > I don't doubt *at all* that you're right about all these sources of > problems on the pluto-p board. The board seems to be designed to > minimize component count, which means that NONE of the methods you > describe to mitigate or fix noise/crosstalk/bounce are on it. My old stepper/PWM boards worked OK on both the mobo and PCI par ports, as did the PPMC board set. The latest version of the stepper/PWM board would not work reliably on the PCI parport. I finally diagnosed it to crosstalk on the WAIT/ signal when too many data lines changed state at the same time. After a LOT of fooling around with timing, I had to put terminators on the data lines and control signals, somthing I'd been avoiding due to complexity, up to that point. Just terminating about 3 of the data lines fixed it, but I terminated 11 signals to be sure. I probably should have always had this, "but it was working, before.....". Termination is 390 Ohms to +3.3 V.
I have been installing this by hand until the next board spin. Jon ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
