Timer interrupt issue with CubeMX generated code, NucleoF722ZE board

NucleoF722ZE board, Stm32CubeMX ver 4.22.1, Eclipse

Version: Neon.3 Release (4.6.3)

I wanted to setup TIM6 as timer interrupt for 400usec sampling loop. In CubeMX : TIM6 clocked at 1Mhz and ARR = 400,

TIM6 Configuration/NVIC settings/Enabled (TIM6 global interrupt), then in NVIC Configuration/enabled TIM6 global interrupt with Preemp Priority=10 and Sub Priority=0. Then Generate code.

 The generated code seemed to be OK, and it also had 

 set NVIC interrupt priority and enable as below.

HAL_NVIC_SetPriority(

, 10, 0);

HAL_NVIC_EnableIRQ(

);

I added code to toggle the LED inside the ISR void TIM6_DAC_IRQHandler (void) and it never triggered.

Result:

TIM6  was counting OK (read TIM6.CNT and outputted on PWM pin for monitoring), but there was  no timer overflow interrupt generated.

However after adding TIM6.DIER = 1; // DMA/interrupt enable, then it worked.

What I need to add TIM6.DIER=1; instead of by CubeMX? or what I did wrong in my steps?

Thanks,

Brian