Subject: Re: [stella] Re: [Fpga2600] Where am I going wrong? From: Adam Wozniak <adam@xxxxxxxxxxxxxxxx> Date: Fri, 3 Jun 2005 08:45:09 -0400 |
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Fri, 3 Jun 2005, Chris Wilkson wrote: > You're using a DSO (digital sampling oscilloscope) and it looks like a > software frob so I don't know if it's real, but you have glitches during > your sync pulses. That's a murder/death/kill right there. A big one. Yeah, I saw those too, and am concerned. I'm still not sure if that's the bitscope being goofy, or if they're real. My DAC is an 8 bit r/2r ladder feeding a high speed op-amp in a unity gain configuration. I used the op-amp because I wasn't sure what the exact load would be or what it would do to the output of the resistor ladder. I thought throwing s very small cap on the output of the resistor ladder might smooth out small glitches. The nearest cap at hand was a .1uF, which of course is way too big. :) Thanks for the advice re: voltage levels. I've tried all kinds of numbers, I'll give yours a run next. I _have_ gotten a good b&w image for sometimes several minutes at a time. I suspect I've got other problems too though; sometimes it looks as if the processor is locking up (My next plan is to look at phi0 and rdy). My PF graphics look close to ok. My P0/P1 graphics are jumping all over the place. My M0/M1 graphics look close to ok. - -- adam@xxxxxxxxxxxxxxxx http://cuddlepuddle.org/~adam KG6GZR http://cuddlepuddle.org/~adam/resume.html -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFCoFCkyvXf5Z0z5zERAr53AJ9IVoZujHfHbeKx7TF0T8UqUBDG/ACgoOBs ArVhMMeHu8+sv7J6meukZK4= =jTPP -----END PGP SIGNATURE----- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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