The question isn't what rate CAN you scan them, it's what rate SHOULD you scan them. The rate of fusion for your eyes is in the range of 45 flashes per second (any slower and you'll see flicker). LED's have little (if any) persistance, unlike a CRT, for instance. So, you should scan the entire display at least 45 (or so) times per second. I usually shoot for around 60 complete scans per second to be safe. LEDs react very quickly, so you can scan a lot faster without affecting the display, but it doesn't buy anything unless you're trying to do something fancy like control the brightness by pulse-width modulating them, and it costs processor overhead (a greater percentage of your total time is spent updating the display). I suspect by the wording of the question that something may be missing, though.... > >This might sound like a stupid question, but at what speed can i drive > >7segment displays?? In my current analogue design i use a 4Hz clock to > pulse > >the displays, but using a pic this is a little difficult. > > > >Will the 7segment display anything at all if i switch them at say once > every > >100 instuctions ( on a 10 Mhz clock )? I suppose it all depends on the duty > >cycle. > > > >Also, do i have to connect anything to the two clock lines in a 16c84 if im > >using the internal clock ? > > > >Thanx > > > > John -- Andrew Pines apines@cosmodog.com http://www.cosmodog.com