If you're satisfied with the frequency, amplitude, power, and precision of the signal you can generate from a PC sound card, that's a terrific way to generate that signal. You already own one or more of 'em, and the characteristics of the output are pretty well understood.

If you need a 100 Mbit per second Manchester-encoded waveform containing a specific repeating bit pattern, from which you need to extract timing within a given time, you might find it quite easy to generate using the method I suggested, but quite tricky with an 805x of any sort. It becomes even trickier if you need, say, an MFM or or 2/7-RLL-modulated bitstream. Those are easy to generate in a state machine but not so easy to create at 100 Mbits/second in an 805x.

What would you recommend, Jan, if one needs a modulated digital bitstream at 250 Mbits/second? It takes just a few minutes, or half an hour to create the logic to convert from a byte stream to a modulated bit stream in CPLD/FPGA software, and a few more minutes to program the component. Then, a simple set of signals from a PC or other control system will turn it on and off, and allow you to operate on it anyway you like. Another thing that you can do with such an arrangement, is to sample the output from a system-under-test, record it into CF, or BBRAM, or whatever, and play it back at your leisure to work out interface/processing details. Though an FPGA may seem to be vast overkill, the fact that it has memory, counters, any imaginable logic, and clock manipulation hardware that will even multiply an external clock up to a required rate for you makes it inherently convenient. After all, you won't wear it out!

RE