BSTAT_CMD
switch (status & (BSTAT_MSG | BSTAT_CMD | BSTAT_IO)) {
case BSTAT_CMD: /* COMMAND OUT */
case BSTAT_CMD | BSTAT_IO: /* STATUS IN */
case BSTAT_MSG | BSTAT_CMD: /* MESSAGE OUT */
case BSTAT_MSG | BSTAT_CMD | BSTAT_IO: /* MESSAGE IN */