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tcantrell
Visitor II
October 13, 2005
Question

Power Down Mode Recovery

  • October 13, 2005
  • 2 replies
  • 711 views
Posted on October 13, 2005 at 12:05

Power Down Mode Recovery

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    2 replies

    T
    tcantrellAuthor
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 12:08

    I need to use Power Down mode to conserve power, but I can't afford to go through reset to recover. Other 8051 derivatives I have used allow the external interrupt to terminate the power down mode. Is there any other way to recover from power down mode without a reset?

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    tcantrellAuthor
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 12:08

    Two problems. One, I have to reinitialize all the peripherals and I have to play games with the startup code to allow some variables to not be initialized after the reset occurs. Second, the signal I need to use to wake the processor is a square wave, which means I'll have to add a one shot or something to shorten the reset pulse. It's actually a real pain, and one that would be easily avoided if the power down mode could be terminated by an external interrupt. Why bother having all the SFRs retain their values during power down mode if you're going to have to reset them anyway? I understand the I/O ports, but the rest of them are lost after the reset. Are the values on the I/O ports lost when the reset occurs?

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