Disable External Watchdog during microcontroller programming

[Hanamant]

Hi Team.

We are facing some challenge with external watchdog timer with STM32F373VCT6 controller. when there is no program in flash input to external watch dog timer (WDI) is output and no pulse . during this time external watch dog timer continuously generate reset pulse to microcontroller pin (nRST which is default of pull up). 

when we trying to program through JLINK external watch dog timer not allowing to program , it continuously resetting the controller, we need to manually separate external watch dog timer reset pin from nRST pin by removing R64 as per given schematic.

 

Do you have any suggestion to avoid manual intervention

[TDK]

I believe removing R64 is the best option.

The NRST signal is hardwired--no way to have the chip ignore it.

You could hardwire NRST to 3V3 if the watchdog chip has limited output capacity and won't be damaged by that. Not really recommended to short NRST to 3V3 but it'll work.

[Andrew Neil]

This is a common issue with any external WD - nothing to do with the STM32, and not specific to the STWD100.

The STWD100 has an Enable pin:

 

[Tesla DeLorean]

From your own code, or ram based loader, you could generate watchdog kick pulses via PB4 TIM16_CH1 or TIM3_CH1

It might have been a better approach to have connected the -EN pin to a programming header or MCU pin