Disc reader project -- quick status update

Jules Richardson wrote: My amiga disk reader doesn't sample at all. I look for falling edges of the pulses, clear a timer, look for the next edge, and calculate the time difference between two pulses. The time between pulses define the data, and I write out the associated data pattern to memory. I've played with PLL's and a few other methods, and I have yet to find one that works better. Differences in frequency and phase really don't have any marked effect on my results --- no need for up/down counters and all that crap. In the amiga world, anyways, the time differences between different data patterns are pretty big. I use an 8-bit timer prescaled 1:2 at 50mhz. So I end up w/ a 40ns timer tick with a 0-~10us count ability. For 500kbps raw MFM datarate, this allows roughly 1us guard band in between the 1us data windows. I could probably optimize this a little better, but in practice it works very well. I've recently bought another inexpensive pc-based logic analyzer (the Saleae Logic), and am getting fantastic statistical information out of exported data dumps. I can process the (also 40ns) raw samples in some very simple programs I've written and I'd like to establish some much more detailed information. Keith