ETH_TCR
EMAC_WRITE(ETH_TCR, 0); // send nothing
EMAC_WRITE(ETH_TCR, 0); // send nothing
EMAC_WRITE(ETH_TCR, m->m_pkthdr.len);
EMAC_WRITE(ETH_TCR, 0); // send nothing
CEMAC_WRITE(ETH_TCR, m->m_pkthdr.len);