In SX Microcontrollers, SX/B Compiler and SX-Key Tool, mgreen wrote:

1) The 30mA figure is for a single I/O pin.  There are additional limits on the total current for a group of 8 I/O pins and the total current for the entire device.  See the datasheet for the SX for these limits.

2) The voltage supplied is normally Vdd or Vss (+ supply or ground) less one saturated MOSFET's voltage drop, typically 0.6V.  Again, see the datasheet for the specifics.

3) I/O pins have 3 states: input, output low, and output high.  The input state is high impedance and is effectively open.  You do have to limit the applied voltage since all I/O pins have protective diodes that conduct to Vdd and Vss if the applied voltage goes more than one diode drop above Vdd or below Vss.

4) There's no MTBF for I/O transitions.  The failure modes all have to do with applying excessive voltage or drawing excessive current (beyond the chip's "Absolute Maximum" ratings).  The SX I/O pins are intended for possible applications involving millions of I/O voltage transitions per second.

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