Mark Butcher

K66 UART1 TX Modulation wit FTM2_CH0 - looks to have an error

Discussion created by Mark Butcher on May 6, 2018
Latest reply on May 11, 2018 by Mark Butcher

Hi All


If I use TPM1_CH0 to multiplex LPUART0 Tx it works as expected:

Here I use the TPM1_CH0 output to generate an accurate break just before a Tx frame (SIM_SOPT5 has 0x00010000 set to select this).


When I did the same on UART1 with FTM2_CH0 there was no effect when SIM_SOPT5 has 0x00000020 set.



However, by chance, I found that there is an effect but it depends on "both" FTM2_CH0 AND FTM2_CH1!


The modulation on UART1 Tx is only present when FTM2_CH0 is low AND FTM2_CH1 is high!

Since I was also using FTM2_CH1 for another reason and it was low it was stopping output (doing the same with TPM1_CH1 didn't do the same - it had no effect).
(If I change the polarity of FTM2_CH1 it doesn't change the output - still does the same).
Since I need FTM2 CH1 (and it is longer than FTM2_CH0) this therefore doesn't allow the operation that is needed (it stops the modulation working).


Is this effect known or expected? Is it an error in the chip?