SUNZILOG_FLAG_TX_ACTIVE
#define ZS_TX_ACTIVE(UP) ((UP)->flags & SUNZILOG_FLAG_TX_ACTIVE)
up->flags &= ~SUNZILOG_FLAG_TX_ACTIVE;
up->flags |= SUNZILOG_FLAG_TX_ACTIVE;
up->flags |= SUNZILOG_FLAG_TX_ACTIVE;
up->flags |= SUNZILOG_FLAG_TX_ACTIVE;