In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Sparks-R-Fun wrote:

Some external clock sources can cause damage if installed while programming.  If in doubt, take them out!

The little blue items with three pins are resonators.  You may leave them installed when you program the SX.  However, when they are in place they prevent the DEBUG feature from being able to control the program execution since they provide a clock signal.  When an external clock source is connected, the SX runs at that clock speed.  For you this will be 4MHz or 50MHz depending on the resonator you select.

The SX-Key has internal clock driver circuitry that can drive your SX at whatever (within reason) frequency you desire.  I believe it is about as accurate as the resonators themselves.

I sounds like you should do your programming with the SX-Key in place using a 4MHz clock.  Use OSCXT2 instead of OSC4MHZ and set your FREQ to 4_000_000.

When you are happy with the functionality of your SX design, you can program (CTRL-P) the SX and then replace the SX-Key with the 4MHz resonator.  If all goes well your circuit should then run on its own without a computer connection!

 - Sparks

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