I have a program which is about 200KB, and I am attempting to run on an MK20FX512, using Codewarrior for the download and debug. When the standard CW generated __init_hardware() runs, and attempts to write to the watchdog unlock register, a hard fault interrupt is generated (by the strh instruction) and the processor is reset.
21 SCB_VTOR = (uint32_t)__vector_table; /* Set the interrupt vector table position */
00000800: ldr r1,[pc,#0x34]
00000804: movw r0,#0xed08
00000808: movt r0,#0xe000
0000080c: str r1,[r0,#0]
35 *(volatile unsigned short *)KINETIS_WDOG_UNLOCK_ADDR = KINETIS_WDOG_UNLOCK_SEQ_1;
0000080e: movw r1,#0xc520
00000812: movw r0,#0x200e
00000816: movt r0,#0x4005
0000081a: strh r1,[r0,#0] // INTERRUPT GENERATED HERE
It is also worth noting that when this same initialization is run in a different project (with smaller code size), no interrupt is generated.
Another interesting fact is that if I refresh the watchdog instead of trying to unlock it, no hard fault is generated, but the processor has another interrupt when it attempts to initialize the stack pointer (after __init_hardware).
// skip stack setup if __SP_INIT is 0
// assume sp is already setup.
add sp,#4 // INTERRUPT GENERATED HERE