OMAP-L138 Internal Pulls

Milan Zelenka

Other Parts Discussed in Thread: OMAP-L138

Hello,
During reset, all IOs are pulled down. After reset, most IOs (except CP26-29) are pull high.

With this approach, one of the states will not match HW requirements upon power-up. Thus, external components must be used for each and every IO pin.

May I ask to explain the rationale behind?

Many thanks,
Milan

over 12 years ago

0 Raja over 12 years ago

TI__Guru* 81335 points

Hi Milan,

Thanks for the post.

I could see the duplicate threads for the same question.

Please follow below threads for answers.

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/133152.aspx

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/279166.aspx

0 Milan Zelenka over 12 years ago in reply to Raja

Intellectual 870 points

Hello Rajasekaran,
neither of the two link addresses the question I raised.

Best,
Milan

0 Milan Zelenka over 12 years ago in reply to Milan Zelenka

Intellectual 870 points

Hello,
May I ask for an update?

Many thanks,
Milan

0 Shankari G over 12 years ago in reply to Milan Zelenka

TI__Mastermind 43955 points

Hi Milan,

The same query is posted at http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/279166.aspx and it seems BrandonAzbell has answered your query.

Please do reply if you are not satisfied with the answer provided by Brandon. I will take your post to TI hardware team to have a closer look to your problem.

May I request you to have a track on one post instead of two? and delete any one of these posts as there are duplicates. Else, Shall I do it for you?

Regards,

Shankari

0 Milan Zelenka over 12 years ago in reply to Shankari G

Intellectual 870 points

Hello Shankari,
It looks like you are trying to combine two different queries. It won't work.

My query:
Please explain why OMAP-L138 applies pulls down during Reset and then pulls up (in most CP groups) in runtime.

Many thanks,
Milan

0 Mukul Bhatnagar over 12 years ago

TI__Guru* 83965 points

Hi Milan

On digging further, the history is as follows.In general there is separate control for pu/pd behavior during / while reset vs during normal functional mode.
For this family of devices , the IO buffers used did not have such separate pull up vs pull down control via separate signals. Instead there was supposed to be option for using separate IO depending on if you wanted pull down vs pull up during reset, the original intent was to match this buffer selection to the default state of the pu/pd coming out of reset.
However due to some issues with the "pull up" version of the IO buffers, they were not incoporated in design and only the "pull down" versions were used.
In general where-ever you want a pull up value on the critical device pins for external use, it is recommended to use external pull ups.

Regards

Mukul

0 Milan Zelenka over 12 years ago in reply to Mukul Bhatnagar

Intellectual 870 points

Hi Mukul,
Clear. Now I understand this is a design issue.
Thanks,
Milan

Processors

Processors forum

OMAP-L138 Internal Pulls