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August 11, 2025
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JTAG STM32H757XIH6

  • August 11, 2025
  • 1 reply
  • 174 views

should the pullups on JTAG should be given for JTAG in STM32H757XIH6, also are there any extra consideration taken care while using ARM JTAG. If pullup is not necessary, why is it so.

Best answer by KDJEM.1

Hello @JananiRamesh;

 

As mentioned in AN4938, the devices embed internal pull-ups and pull-downs to ensure correct JTAG behavior. The following pins are consequently not left floating during reset and they are configured as follows until the user software takes control of them:
• NJTRST: internal pull-up.
• JTDI: internal pull-up.
• JTMS/SWDIO: internal pull-up.
• TCK/SWCLK: internal pull-down.
If these I/Os are externally connected to a different voltage, leakage current will flow during and after reset, until they are reconfigured by software. 

You can find in the below figure JTAG connector implementation.

KDJEM1_0-1754914409925.png

 

I hope this answer you request!

 

Thank you.

Kaouthar

 

1 reply

KDJEM.1
KDJEM.1Best answer
Technical Moderator
August 11, 2025

Hello @JananiRamesh;

 

As mentioned in AN4938, the devices embed internal pull-ups and pull-downs to ensure correct JTAG behavior. The following pins are consequently not left floating during reset and they are configured as follows until the user software takes control of them:
• NJTRST: internal pull-up.
• JTDI: internal pull-up.
• JTMS/SWDIO: internal pull-up.
• TCK/SWCLK: internal pull-down.
If these I/Os are externally connected to a different voltage, leakage current will flow during and after reset, until they are reconfigured by software. 

You can find in the below figure JTAG connector implementation.

KDJEM1_0-1754914409925.png

 

I hope this answer you request!

 

Thank you.

Kaouthar

 

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