Unexpected USART TCI

[jo_it]

Posted on March 27, 2015 at 18:05

I'm on a Nucleo-F411RE board and experience strange behaviour. In the USART interrupt pass I have status flag of TCI set. The TCIE bit is never set in the CR1 reg?

I start to get doubts I need to pull this flag high to disable TCI?

[Tesla DeLorean]

Posted on March 27, 2015 at 18:20

The logic in the peripheral observes a TC event the flag gets to this register, it doesn't generate an interrupt because it's not gated with the enable. Ignore it.

And RXNE, and TXE, interrupts will also flag, whether enabled or not.

Figure AND get on the enable, and an OR gate combining all sources, single IRQ feed to the NVIC.

[Tesla DeLorean]

Posted on March 27, 2015 at 18:28

Observe there isn't a 'TCI' bit in the status register.

[jo_it]

Posted on March 27, 2015 at 18:28

@clive: offcourse, they will flag status anyhow. If the code can't ignore TC flag it must check whether status is set and his compatible bit in CR1 reg. tnx!