JTAG Communication Failure when Changing to External OSC

 Internal clock works perfectly fine.

I commented IntOsc1Sel(); and enabled XtalOscSel();, then changed PLL #define DSP28_PLLCR    9 // Uncomment for 90 MHz devices [90 MHz = (20MHz * 9)/2].

After downloading the program and running the program, no update to the watching window and everything is 0.

Debugger XDS100 is used.

But it worked randomly once a while.

CRYSTAL 300-8214-1-ND is used and two 15pf CG0 cap is used. 

// IntOsc1Sel();
   XtalOscSel();