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

In general, it is a good idea to have current-limiting resistors in series with the SX I/O lines in order to protect the I/O pins as well as external components connected to them.

There is no specific reason to use the RA pins as outputs with the only exception that the RA pins when used as outputs do have a symmetric output swing, i.e. the voltage drops across the internal high-end and low-end drivers are the same for a certain output current.

Per definition, all ports are automatically configured as inputs, i.e. with high-Z at power-on. The same is true for port A, so I don't see a reason why not using is for reading a 4-digit DIP switch as this nicely matches the 4 RA pins. Although not really necessary, series resistors would not harm here. On the other hand, when the DIP switch segments pull down to Vss, don't forget to attach pull-up resistors to Vdd (or activate the port-internal "weak pull-up" resistors. When the DIP switch segment pull high to Vdd, you will need to add external pull-down resistors to Vss.

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