Try this, or the other F4 examples as a basis, I know you said 431, they are all much the same
STM32Cube_FW_F4_V1.23.0\Projects\STM32F413ZH-Nucleo\Examples\TIM\TIM_PWMOutput\Src\main.c
Perhaps use PMW2 mode, inverts the pulse polarity sense.
You'd configure PB6, AF mode associating with TIM16
Divide down the APB clock for TIM to get to 200 KHz, use Prescaler and Period to factor.
Assume a TIMCLK of 84 MHz,
Prescaler = 0; // DIV1
Period = (84000000 / 200000) - 1;
For 50/50 duty Pulse = (Period+1) /2;
