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boris239955
Visitor II
December 6, 2005
Question

Information needed on STANDBY mode

  • December 6, 2005
  • 9 replies
  • 1517 views
Posted on December 06, 2005 at 05:30

Information needed on STANDBY mode

    This topic has been closed for replies.

    9 replies

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    boris239955Author
    Visitor II
    July 22, 2005
    Posted on July 22, 2005 at 15:07

    Hi all,

    There are a few things I'm not sure about regarding STANDBY mode.

    The datasheet says ''All the I/Os belonging to the kernel are forced into High Impedance''. Does that mean ALL I/O pins, or are there exceptions (e.g. EMI, pins configured as Alternate Functions, etc.) ?

    Also, it says that the system RAM is cleared. What happens to the internal registers ? Do they all retain their values, or are some reset to the default values (e.g. I/O pins config, clock config...) ?

    Basically, I want to be able to power-down my system by software, and restart it with the WAKEUP pin. I'm thinking about doing the following :

    * On power-down :

    - switch to the 32 kHz oscillator

    - power-down my external oscillator (connected to the CK pin)

    - activate the STANDBY mode

    * On wake-up :

    - switch back to the external oscillator

    - restart the program

    Is this going to work as expected ?

    Any info will be greatly appreciated !

    :D

    H
    hichem2
    Visitor II
    July 26, 2005
    Posted on July 26, 2005 at 09:38

    Hello,

    The STANDBY sequence is initiated either:

    – by setting the PWRDWN bit in the PCU_PWRCR register (software STANDBY entry)

    – or by externally forcing the nSTDBY pin to ‘0’ (hardware STANDBY entry).

    Caution: You have to manage the nSTDBY, WAKEUP and RESET pin states in order to enter or exit STANDBY mode (refer to the STR71x reference manual, STANDBY section).

    Cheers

    Hich ;)

    B
    boris239955Author
    Visitor II
    July 26, 2005
    Posted on July 26, 2005 at 10:45

    Hi Hich,

    Thanks for your reply.

    I understand how to initiate standby mode (I'll be using the software entry), but I'm still not sure about the high-impedance thing, and whether all registers values are preserved when restarting from standby.

    I'm currently designing a protoype board, and I'll like to be sure that my understanding is correct before finalizing the PCB :)

    H
    hichem2
    Visitor II
    July 26, 2005
    Posted on July 26, 2005 at 10:50

    Hi Fizlo,

    Core, memories and peripherals not powered by 1.8V internal supply.

    Cheers,

    Hich :D

    B
    boris239955Author
    Visitor II
    July 26, 2005
    Posted on July 26, 2005 at 11:02

    Sorry to bother you again Hich,

    So if I understand correctly your reply,

    - All I/O pins switch to high-impedance

    - All registers values are preserved

    - Only the RAM is cleared

    Right ? 8-)

    H
    hichem2
    Visitor II
    July 26, 2005
    Posted on July 26, 2005 at 11:09

    Hi,

    Right, just All I/Os are forced to high impedance except the Standby I/Os(nSTDBY, nRSTIN, WAKEUP, RTCXTI and RTCXTO.).

    ciao,

    hich

    B
    boris239955Author
    Visitor II
    July 26, 2005
    Posted on July 26, 2005 at 11:29

    Thank you very much, Hich ! :D

    H
    hichem2
    Visitor II
    July 28, 2005
    Posted on July 28, 2005 at 06:46

    Hi,

    You are welcome.

    Cheers,

    Hich :p

    H
    hichem2
    Visitor II
    December 6, 2005
    Posted on December 06, 2005 at 05:30

    Hi,

    After wake-up from the standby mode only the RTC data are preseved, RAM and all the others peripherals data are cleared.

    Best regatds,

    Hich 8-)

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