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

Bean,

I completely feel with you...

A couple of days, I also was close to loosing a lot of my hair.

For a customer's project I designed a simple circuitry around an SX20 with a 4 MHz crystal, and a 1 MOhm resistor parallel to the crystal. I also added the typical "Vss-Vdd-OSC2-OSC1" 4-pin header for the SX-Key/Blitz. Next, my customer took care of designing the PCB.

When I tried to program the first assembled sample board for testing, I got a "Vpp generation failed" error.

Usually, such an error comes up when some excessive load exists on the OSC1 pin. I double-checked the board but could not find any cause for such a load. Just to be sure, I removed the 4MHz crystal, and the 1 MOhm resistor - no success at all.

Want to know the cause for this problem? Well, it took me a while to figure out: The PCB designer interchanged the OSC1 and OSC2 pins on the 4-pin header - Arghhhh !!!

The good news: The on-board SX20 survived!

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