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

Thomas,

fortunately, at power-on or reset, all SX I/O pins are automatically configured as inputs, until the software clears certain bits in the port's TRIS registers. So it is up to your software to make sure that no interconnected I/O pins generate offending states. If this is not the case, I think series limiting resistors are not required.

If you want to add resistors as an additional safety measure, let's assume the worst case: One output pin being low (0V) and the other pin being high (+5V). According to the SX datasheet, the max. allowable sink or source current per I/O pin is 45mA. A resistor of 111Ohm would limit the current to that value. So, a value between 150 and 220Ohm would be fine.

During the relatively long time I'm prototyping SX-based applications, it happened more than once that I had shorts on output pins, and so far, this never destroyed any of my SXes. Seems as if the output circuits are relatively robust, and possibly have some internal current protection. Nevertheless, I don't want to encourage you to ignore output protection :-) .

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