Dunno, but (in general) you probably need an external brownout circuit to protect the SRAM from errant CPU activity during periods when the power supply voltage is not sufficient to guarantee proper operation.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Hi there!
Searched the net without success on this one: Does SRAM content stay the same after reset or various levels of power down on the AtMega8 AVRs. Not concerned about registers, just the SRAM area.
There used to be a blurb on this topic on AVRfreaks, I vaguely remember some kind of errata warning about SRAM getting corrupted. Of course right now I can't get to the site (seems to be down).
Hope someone has some hands-on experience on this one.
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Sure, I have taken care of that, it will go into sleep or power down mode via interrupt when the battery backup kicks in, to preserve power. I'm just not sure whether I can trust the SRAM to stay the way it was before going into sleep.
Generally some AVR's work with this and some don't. 8515 doesn't, for example.
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"SioL" schreef in bericht news:n9xge.12076$ snipped-for-privacy@news.siol.net...
Most newer AVRs contain a brownout detector, so this should protect the SRAM. The SRAM is not really reset like the registers. But there is a certain minimum voltage for the SRAM to retain its contents. If the power supply goes below this, the contents can't be trusted anymore.
If you're just putting the AVR into sleep frequently to conserve power, it will retain the SRAM, otherwise sleep modes would be quite useless. I think SRAM contents are retained between resets (no brownouts).
Jeroen
Sounds good. However, I remember reading some kind of "errata" at avrfreaks.net for the Mega8, addressing sleep modes and memory/register retention. Unfortunately they're down right now so I can't confirm it :(
Not all AVR's are created equal.
-- Siol ------------------------------------------------ Rather than a heartless beep Or a rude error message, See these simple words: "File not found."
In article , SioL writes
On the mega8's I have used, the SRAM is preserved during reset and sleep, but is undefined on power up or after vcc drops below the minimum rated voltage.
-- Tim Mitchell
is undefined on power up or after vcc drops below
Now that's what I was looking for. Thanks!
-- Siol ------------------------------------------------ Rather than a heartless beep Or a rude error message, See these simple words: "File not found."
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