2009-07-20 11:49:48     Power Management mode and Blackfin 537

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2009-07-20 11:49:48     Power Management mode and Blackfin 537

Vincent Le Cam (FRANCE)

Message: 77745   




When putting the BF537 of the stamp linux board in sleep mode (but not in sleep_deeper mode !!!) the power consumption decreases, that's ok but SCLK does'nt occur any more !


We followed the sample program, putting BF537 in sleep mode and being reactivated  by a simple GPIO push...and we added a simple DMA SPI continous reading operation. Everything is OK except that when in "sleep mode", our SPI SCK stops !!!


But documentation says:


Sleep Mode (High Power Savings) - The sleep mode reduces power dissipation by disabling the clock to the processor core (CCLK). The PLL and system clock (SCLK), however, continue to operate in this mode. Typically an external event or RTC activity will wake up the processor. When in the sleep mode, system DMA access to L1 memory is not supported.


Does someone has verified what is specified here (  docs.blackfin.uclinux.org/doku.php?id=power_management_support) ?


It seems to be a contradiction, no ? because SPI CLK is supposed to be based on SCLK.


We use 2008R1.5 is it ok for that operation or should we use a recent distribution such as RC2009 ?


thanks a lot if anybody has an answer...






2009-07-20 11:55:50     Re: Power Management mode and Blackfin 537

Mike Frysinger (UNITED STATES)

Message: 77746   


i think you misunderstand the architecture.  SCLK continues to exist which means the system peripherals retain state, but there is nowhere for reads to be stored.  external memory is in self-refresh which means nothing can access it, and core memory isnt available either.