I don't know if the pin 15 (VDDF on XEP100) connected to VCC could induce "illegal BP"? it seems to be!
Illegal_BP is a typical SW thing. ILLEGAL_BP means that debugger get lost (MCU behavior is different from behavior which debugger expects). Typical root cause is unexpected interrupt or BDM communication lost.
This is usually generated by the following causes:
_ unmapped interrupt vectors
_ jump, read or write to unimplemented addresses (could be due to inappropriate libraries).
_ stack overflow
On the other hand, the VDDF is the voltage regulator (VREG_3V3) output. It is the power supply for NVM logic. The VDDF pins should NOT be connected to VCC. Actually, decoupling capacitors (220 nF, X7R ceramic) should be connected to VDDF pin.
Retrieving data ...