FEC_TCNTRL_FDEN
tcntrl &= ~FEC_TCNTRL_FDEN;
tcntrl |= FEC_TCNTRL_FDEN; /* FD enable */
tcntrl = FEC_TCNTRL_FDEN; /* FD enable */
FS(fecp, x_cntrl, FEC_TCNTRL_FDEN); /* FD enable */
FC(fecp, x_cntrl, FEC_TCNTRL_FDEN); /* FD disable */