Thursday, April 26th 2018, 9:42am UTC+2

You are not logged in.

  • Login
  • Register

canyon81

Beginner

Date of registration: Apr 16th 2018

Posts: 2

1

Monday, April 16th 2018, 9:15am

[SOLVED] Structure of SWDIO pad of J-Link/J-Flash

Hi!
Is Segger J-Link/J-Flash using a push-pull driver or open-drain on the SWDIO pad?
Reason for my question is that the uController we are interfacing as an internal pull-down on SWDIO - which is against the recommendation in the ARM Debug Interface Architecture Specification, section 4.4.2 where a pull-up is required.
When we put an external pull-up there is the problem of getting an intermediate voltage level (due to the internal pull-down) on SWDIO and cross-current. So, we want to get rid of the external pull-up and use only the pull-down. My understanding is, that the pull resistor is required to avoid SWDIO floating when no debugger is connected, which is also achieved by a pull-down. A pull-up is required in case the debugger is using an open-drain driver instead of push-pull.
We already tried removing the external pull-up an Segger J-link still works, so I guess J-lInk uses a push-pull driver - just wanted to get the confirmation for this.
Thanks,
Christian

SEGGER - Nino

Super Moderator

Date of registration: Jan 2nd 2017

Posts: 960

2

Monday, April 16th 2018, 10:05am

Hello Christian,

Thank you for your inquiry.
Correct, J-Link is configured push-pull.

Best regards,
Nino
Please read the forum rules before posting: Forum Rules

Keep in mind, this is not a support forum. Its main purposes is user to user interaction.
Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
Should you be entitled to support contact us per e-mail.
The following contact form can be used for this: https://www.segger.com/about-us/contact-us/


canyon81

Beginner

Date of registration: Apr 16th 2018

Posts: 2

3

Monday, April 16th 2018, 11:45am

Hi Nino,
thanks a lot for quick reply and confirmation. This solves my issue.
Christian

SEGGER - Nino

Super Moderator

Date of registration: Jan 2nd 2017

Posts: 960

4

Monday, April 16th 2018, 12:01pm

Hello Christian,

Great to hear that your issue is resolved.
We will consider this thread as solved now.

Best regards,
Nino
Please read the forum rules before posting: Forum Rules

Keep in mind, this is not a support forum. Its main purposes is user to user interaction.
Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
Should you be entitled to support contact us per e-mail.
The following contact form can be used for this: https://www.segger.com/about-us/contact-us/