STAT_TX_THLD
if (status & STAT_TX_THLD)
pio->enabled_irqs &= ~STAT_TX_THLD;
if (!(pio_reg_read(INTR_STATUS) & STAT_TX_THLD))
if (!(pio_reg_read(INTR_STATUS) & STAT_TX_THLD))
pio->enabled_irqs |= STAT_TX_THLD;