MFP_IERB
mfp_base[MFP_IERB] = ((u_int8_t) (a))
#define mfp_get_ierb() (mfp_base[MFP_IERB])
#define mfp_bit_set_ierb(bits) mfp_bit_set(MFP_IERB, (bits))
#define mfp_bit_clear_ierb(bits) mfp_bit_clear(MFP_IERB, (bits))