> A consideration with RS232 is that the signals swing to either side of 0, so$
It's been a while since I read the spec, but I think it's -3 to -20 volts one way and +3 to +20 the other, with the -3 to +3 range deliberately left ambiguous. I think there are slew rate limits, too, but I don't recall what they are even approximately. Of course, serial lines are normally run over unshielded wires with a single shared signal ground, so, for noise tolerance, transmitters usually drive the outputs substantially beyond 3V either side of ground. (There are also short-circuit tolerance specs which mean you don't want your output impedance to be too low, either. I think it's something like, any pins or ccombinations of pins may be shorted to one another and/or any voltage or voltages from -20 to +20 indefinitely without damage.) /~\ The ASCII Mouse \ / Ribbon Campaign X Against HTML mo...@rodents-montreal.org / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
