GPIO Status when AM335x in STANDBY Mode

LeonardEllis

GPIO bits that are set and functioning, then the AM2335x transitions to STAND-BY mode, what happens to the GPIO bits? If I have one set to '0' and it is sinking current, another set to '1' and it is sourcing, do these continue to retain this state when in Standby? I searched the TRM and the Datasheet, this condition does not seem to be addressed, or have I overlooked something? Is there another technical document or wiki page I have not discovered that explains this situation? If so, please advise.

~Leonard

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

What software are you using?

0 LeonardEllis over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 71526 points

At this time, I don't know the software base - but why would that matter? If a GPIO pin is set to a '1' or '0' state, why would the code matter?

0 Biser Gatchev-XID over 9 years ago in reply to LeonardEllis

TI__Guru**** 393215 points

I'm asking because there is IO Pad Configuration for low-power modes in the Linux SDK: processors.wiki.ti.com/.../Linux_Core_Power_Management_User's_Guide_(v4.1)

0 LeonardEllis over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 71526 points

Thanks for this link, but it still does not tell me how a GPIO pin behaves when the processor goes into Standby mode. It discusses waking up from SLEEP mode with an INPUT from GPIO0 only, but makes not mention of output bit settings. There is some notation concerning VTT regulator EN/OFF, but I don't see how this relates to GPIO. I believe the system is using Linux, but again, what does that have to do with the GPIO output settings and what happens when Standby is entered?

~Leonard

0 Biser Gatchev-XID over 9 years ago in reply to LeonardEllis

TI__Guru**** 393215 points

General processor state in Standby mode can be seen in Table 8-13 and section 8.1.4.3.2 from the AM335x TRM Rev. M. You can see there that all GPIO banks are active in Standby.

0 LeonardEllis over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 71526 points

Yes, I read that table, and the description in 8.1.4.3.2, but it only discusses WAKEUP by using any GPIO. The table simply says "Wakeup from any GPIO" and since we are in Standby mode, this would mean toggling an Input that is tied to an INT. There is no description of the question at hand:

What happens to the OUTPUT bits set at the GPIO pin when STANDBY is initiated? Do they continue to source or sink current, or do they go to a high-impedance (or some other) state? This question is not answered in the TRM or the datasheet.

0 Biser Gatchev-XID over 9 years ago in reply to LeonardEllis

TI__Guru**** 393215 points

They remain as they are set, unless you take care of them as described in the wiki link above (for Linux).

0 LeonardEllis over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 71526 points

and where is this documented? How is a designer to know? and what if they are not using Linux?

0 Biser Gatchev-XID over 9 years ago in reply to LeonardEllis

TI__Guru**** 393215 points

I cannot answer your first question. You can ask the BU. As for not using Linux, this forum does not support third-party software.

0 Michael Erdahl over 9 years ago in reply to Biser Gatchev-XID

TI__Genius 13505 points

Leonard,

The peripheral and wakeup power and clock domains are still active during standby, so GPIO states will not be affected. The TRM does not explicitly state this relationship explicitly- it is something we can improve.

GPIO changing from programmed padconf state to HiZ only occurs on suspend (deep sleep 0).

Regards,
Mike

0 LeonardEllis over 9 years ago in reply to Michael Erdahl

TI__Guru 71526 points

Thank you for the explanation, Mike. I would encourage us to improve the description in the TRM/Datasheet to explain this - thanks!

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GPIO Status when AM335x in STANDBY Mode