AM18XX_TIMER1_TIM12
prev = bus_space_read_4(bst, bsh, AM18XX_TIMER1_TIM12);
cur = bus_space_read_4(bst, bsh, AM18XX_TIMER1_TIM12);
bus_space_write_4(bst, bsh, AM18XX_TIMER1_TIM12, 0);