SIREG_FIFO_CNTH
SIREG_WRITE(ncr_sc, SIREG_FIFO_CNTH, 0);
SIREG_WRITE(ncr_sc, SIREG_FIFO_CNTH, 0);
SIREG_WRITE(ncr_sc, SIREG_FIFO_CNTH, (uint16_t)(xlen >> 16));
resid = SIREG_READ(ncr_sc, SIREG_FIFO_CNTH) << 16;
SIREG_WRITE(ncr_sc, SIREG_FIFO_CNTH, 0);