TMS320F28375S: About the JTAG port when standalone

Sh.Sasaki

Part Number: TMS320F28375S

Hi experts,

My customer uses a digital isolator IC for the JTAG port(TMS,TDI,TDO,TCK), and due to the influence of this IC, the JTAG port is fixed to Low when standalone.
Is this design okay?
If this design is incorrect, I would like to know other ideas.

Best regards,
Sasaki

over 3 years ago

0 Sh.Sasaki over 3 years ago

Guru 13625 points

Does anyone have any information?

0 Nirav Ginwala over 3 years ago

TI__Genius 15385 points

Hi Sasaki - Let me assign this post to an expert, you should see a response soon.

Best Regards,

Nirav

0 Cody Watkins over 3 years ago

TI__Mastermind 41335 points

Sasaki-San,

I believe this would be OK, please allow me some time to confirm.

For now, please confirm if any of these pins toggle during the power on process.

Can you also confirm that TRSTn has the correct pull-down resistor?

Thanks,
Cody

0 Sh.Sasaki over 3 years ago in reply to Cody Watkins

Guru 13625 points

Hi Cody-san,

Thank you for your reply.

Cody Watkins said:
I believe this would be OK, please allow me some time to confirm.

Please let me know if you get new information.

Cody Watkins said:
For now, please confirm if any of these pins toggle during the power on process.

Can you also confirm that TRSTn has the correct pull-down resistor?

I confirm the above with my customer.

Best regards,
Sasaki

0 Sh.Sasaki over 3 years ago in reply to Cody Watkins

Guru 13625 points

Hi Cody-san,

Cody Watkins said:
For now, please confirm if any of these pins toggle during the power on process.

Can you also confirm that TRSTn has the correct pull-down resistor?

I confirmed the above with my customer.

My customer's environment is below.

Those pins stay low during the power on process.
TRSTn pin has the correct pull-down resistor(2.2kΩ).

Best regards,
Sasaki

+1 Cody Watkins over 3 years ago in reply to Sh.Sasaki

TI__Mastermind 41335 points

Sasaki-San,

As long as the TRSTn pin is held low this will not cause any device issues. TRSTn will hold the JTAG logic in reset and avoid any issues.

Some JTAG pins have weak internal pull ups, so there will be some wasted power if your isolation device is forcing these pins low. This will not cause a functional issue though.

Regards,
Cody

0 Sh.Sasaki over 3 years ago in reply to Cody Watkins

Guru 13625 points

Hi Cody-san,

Thank you for your answer!
I understood it.

Best ragaards,
Sasaki

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TMS320F28375S: About the JTAG port when standalone