Hello everyone,

I bought C8051F020 Eva board and tried some programming. But I got problem when I tried to switch to external clock on the board (crystal freq. is 22.1184M). My clock config function is as following:

...

void change_to_ext_clk(void){
unsigned int i;

OSCXCN=0x67; //crystal as osc, freq>6.7M
for(i=0;i<10000;i++)
i=i; // wait more than 1ms
while((OSCXCN & 0x80)==0); //Poll ext clk valid bit
OSCICN=0x80; // switch to external clock
}

The problem is that the program stuck at check the exteral clock valid bit. I use a oscilloscope to check both ends of the crystal, there are no sine wave at all, but a DC voltage of about 1V at both ends. This DC volage is not present after reset when using interal clock but appears after OSCXCN=0x67 is executed. Because there is no oscillation, the XTLVLD bit never goes up.

These four steps follow the suggestion of Cygnal's data sheet on page 138. Did I miss anything at setting things up?

Thank you for your help.

Simon