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

William,

the SX datasheet specifies the absolute maximum voltage applied to any input as Vdd + 0.6 Volt. Inside the SX, there are clamping diodes to protect the inputs from overvoltage. So a resistor in series with an input, like a 10 kOhm between MCLR/ and Vdd mainly protects the claming diodes in case of an overvoltage on the input. The resistor limits the current flowing through these diodes. You may use a smaller value, say down to 470 Ohm.

BTW, especially when building prototypes, it is a good idea to put 470 Ohm resistors in series with all port input pins as well, for the same reason.

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