IA_TIMA
MFP->mf_iera &= ~IA_TIMA; /* Disable timer interrupts */
MFP->mf_ipra = (u_int8_t)~IA_TIMA;/* Clear pending interrupts */
MFP->mf_iera |= IA_TIMA; /* Enable timer interrupts */
MFP->mf_imra |= IA_TIMA; /* ..... */
if (ipra & IA_TIMA)