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

Kramer,

You are right, when programming a chip, the SX-Key applies about 12V (Vpp) to the OSC1 pin. This programming voltage is generated on-board by the SX-Key. When the SX-Key supply voltage is too low, it is possible that Vpp does not reach 12V, and the chip can't be programmed though. This is another reason why the SX-Key supply should be 5V. Any method to split the two supply voltages (5V for the SX-Key, and 3.3V for the target board) will do, including 2-3 inch jumper wires for OSC1 and OSC2, although I can only recommend this for programming as frequencies are relatively low but not for debugging/running/clocking with the SX-Key as frequencies may by as high as 50 MHz or even higher.

I don't think that Dave recommended adding an on-board 5V regulator that would ony be activated for programming the SX but he meant feeding 5V from an external source. Again, this would only be an option when all components on the target board can stand the 5V.

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