With the transmit enable bit (TE) that controls initialization of transmission of the second packet onwards set to 1, check that the state of the transmit interrupt enable bit (TIE) hasn't changed from 0 to 1.
The following conditions must be met in order to control initialization of serial transmission of the second packet onwards using the TE bit.
- 1 can only be written when the TE bit = the RE bit = 0.
- If either of the TE or RE bits is once set to 1, after that it is only possible to write TE bit = RE bit = 0.
To avoid the above restrictions, don't use the TIE bit to control serial transmission, and set interrupt enable/disable using the interrupt request enable registers (IER) in the interrupt control unit (ICU).