FXP_CB_COMMAND_NOP
tcbp[i].cb_command = htole16(FXP_CB_COMMAND_NOP);
tcbp->cb_command = htole16(FXP_CB_COMMAND_NOP | FXP_CB_COMMAND_S);
CSR_WRITE_1(sc, FXP_CSR_SCB_COMMAND, FXP_CB_COMMAND_NOP);