SCA_CDAL0
cda = dmac_read_2(scp, SCA_CDAL0);
dmac_write_2(scp, SCA_CDAL0, (u_int16_t)(scp->sp_rxdesc_p & 0xffff));
bus_space_write_2(iot, sca_ioh[0], SCA_REG(SCA_CDAL0), 0);
tmp = bus_space_read_2(iot, sca_ioh[0], SCA_REG(SCA_CDAL0));
bus_space_write_2(iot, sca_ioh[0], SCA_REG(SCA_CDAL0), 0x55AA);
tmp = bus_space_read_2(iot, sca_ioh[0], SCA_REG(SCA_CDAL0));