That's interesting. If bi-directional, can you tell the difference between waveform generated by each end? Looking at the traces, the first thing I worry about is whether the instrument you're using is sufficiently reliable and without sample jitter. I guess you've tested it with a square wave of a fixed frequency representative of what is on line X? Otherwise, it looks like real data, and I'd love to see several captures in parallel with the same time base. --=20 James Cameron http://quozl.linux.org.au/ --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .