Thank you Martion,
Do you have the doc of e200z420? Dose e200z420 have the time base register? Because when I execute "asm("mtspr 284, %%r3 \n\t"::);", it will occur IVOR6 exception.
void GetTBL_start(void)
{
/****************
// Clear Timebase
****************/
asm("e_li %%r3, 0 \n\t"::);
asm("mtspr 284, %%r3 \n\t"::);
/* read tbl */
asm("mfspr %%r3, 268 \n\t"::); /* TBL */
}