The USART status reg has 2 Tx flags:
-bit 6 Txcomplete (TXCIF)
-bit 5 Datareg empty (DREIF)
For sending a byte, polling DREIF
until =1 then sending data works (no interrupt)
Using TXCIF instead of DREIF does not work
The datasheet mentions data can be written only if DREIF=1
so there must be a delay between TXCIF=1 and DREIF=1
For interrupt driven Tx I want to use TXCIF-int because DREIF can
not be cleared without writing new data.
Should I wait for DREIF in the TXCIF-int before sending and
how much is the delay?
What is the purpose of TXCIF?