Reliability of a microcontroller in sleep mode

I was wondering how people deal with the following problem. 

When a microcontroller is put in sleep mode many registers and RAM are
in an initialized state. In this condition the microcontroller can be
affected by ESD, EMI which means the initialization can be corrupted
-> there is a risk it does not wake up anymore.

Of course there are watchdogs, but due to power constraints this can
not be on during sleep.

Is there anybody who has experience with this kind of problems ?

MarcelG

"Marcel-G" <marcel-g@xs4all.nl> wrote in message
news:1a53e44a.0404182358.1a7fa3ce@posting.google.com...
> I was wondering how people deal with the following problem.
>
> When a microcontroller is put in sleep mode many registers and RAM are
> in an initialized state. In this condition the microcontroller can be
> affected by ESD, EMI which means the initialization can be corrupted
> -> there is a risk it does not wake up anymore.
>
> Of course there are watchdogs, but due to power constraints this can
> not be on during sleep.
>
> Is there anybody who has experience with this kind of problems ?
>
> MarcelG

Just curious, how would this be different from being in running state? Is
there any reason to suspect higher susceptibility to EMI/ESD corruption in
sleep mode?

Rob

On Mon, 19 Apr 2004 10:47:50 +0200, "Rob Turk" <wipe_me_r.turk@chello.nl> wrote:

>"Marcel-G" <marcel-g@xs4all.nl> wrote in message
>news:1a53e44a.0404182358.1a7fa3ce@posting.google.com...
>> I was wondering how people deal with the following problem.
>>
>> When a microcontroller is put in sleep mode many registers and RAM are
>> in an initialized state. In this condition the microcontroller can be
>> affected by ESD, EMI which means the initialization can be corrupted
>> -> there is a risk it does not wake up anymore.
>>
>> Of course there are watchdogs, but due to power constraints this can
>> not be on during sleep.
>>
>> Is there anybody who has experience with this kind of problems ?
>>
>> MarcelG
>
>Just curious, how would this be different from being in running state? Is
>there any reason to suspect higher susceptibility to EMI/ESD corruption in
>sleep mode?
>
>Rob
>

In many cases it will be in sleep mode for the vast majority of time, and therefore statistically
more likely that an upset event will occur in sleep mode. 
However the wake-up event is unlikely to be affected, as there will typically only be a couple of
hardware bits that control this, and the application could perform some consistency checks
immediately after wake up. e.g. do a checksum on RAM before going to sleep, and check it on wake-up.
However you can never cover all bases in software, and it is far better to ensure that the hardware
is reliable so upssets don't occur in the first place. 

On 19 Apr 2004 00:58:05 -0700, marcel-g@xs4all.nl (Marcel-G) wrote:

>I was wondering how people deal with the following problem. 
>
>When a microcontroller is put in sleep mode many registers and RAM are
>in an initialized state. In this condition the microcontroller can be
>affected by ESD, EMI which means the initialization can be corrupted
>-> there is a risk it does not wake up anymore.
>
>Of course there are watchdogs, but due to power constraints this can
>not be on during sleep.
>
>Is there anybody who has experience with this kind of problems ?
>
>MarcelG

In my uninformed opinion, I think it would be extremerly unlikely to
get corruption of static RAM memory while in sleep mode.  I think this
because the static RAM is inherrently a very stable circuit. It is
much more likely to get corrupted in the presense of all those
fast-rising voltages and transient currents that whizz around the
processor die in normal opration.

regards,
Johnny.

On 19 Apr 2004 00:58:05 -0700, the renowned marcel-g@xs4all.nl
(Marcel-G) wrote:

>I was wondering how people deal with the following problem. 
>
>When a microcontroller is put in sleep mode many registers and RAM are
>in an initialized state. In this condition the microcontroller can be
>affected by ESD, EMI which means the initialization can be corrupted
>-> there is a risk it does not wake up anymore.
>
>Of course there are watchdogs, but due to power constraints this can
>not be on during sleep.
>
>Is there anybody who has experience with this kind of problems ?

You can refresh the initialization from time to time, or even at every
wake-up. 

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

> > When a microcontroller is put in sleep mode many registers and RAM are
> > in an initialized state. In this condition the microcontroller can be
> > affected by ESD, EMI which means the initialization can be corrupted
> > -> there is a risk it does not wake up anymore.
> >
> > Of course there are watchdogs, but due to power constraints this can
> > not be on during sleep.
> >
> > Is there anybody who has experience with this kind of problems ?
> >
> > MarcelG
> 
> Just curious, how would this be different from being in running state? Is
> there any reason to suspect higher susceptibility to EMI/ESD corruption in
> sleep mode?
> 
> Rob

If a microcontroller can run permanently in running state some clock
is running and the power consumption is higher then in sleep.
So during running state it is usually not a problem from power
consumption point of view to have  a watchdog running.

I`m talking about a device which can be a year in sleep, used for a
few minutes and sleep again for a long time.

Marcel

> >>
> >> When a microcontroller is put in sleep mode many registers and RAM are
> >> in an initialized state. In this condition the microcontroller can be
> >> affected by ESD, EMI which means the initialization can be corrupted
> >> -> there is a risk it does not wake up anymore.
> >>
> >> Of course there are watchdogs, but due to power constraints this can
> >> not be on during sleep.
> >>
> >> Is there anybody who has experience with this kind of problems ?
> >>
> >> MarcelG
> >
> >Just curious, how would this be different from being in running state? Is
> >there any reason to suspect higher susceptibility to EMI/ESD corruption in
> >sleep mode?
> >
> >Rob
> >
> 
> In many cases it will be in sleep mode for the vast majority of time, and therefore statistically
> more likely that an upset event will occur in sleep mode. 
> However the wake-up event is unlikely to be affected, as there will typically only be a couple of
> hardware bits that control this, and the application could perform some consistency checks
> immediately after wake up. e.g. do a checksum on RAM before going to sleep, and check it on wake-up.
> However you can never cover all bases in software, and it is far better to ensure that the hardware
> is reliable so upssets don't occur in the first place.
>
>
A microcontroller is most susceptible at the parts which are at the
outer side of the die ( usually I/O ports ). If an I/O register is
changed for example from Input to output while it`s in sleep mode for
an interrupt from that pin it never will wake up.

So I wonder how usually id dealt with this issue for parts which have
to be in sleep without replacable battery for a very long time ( for
eample TPMS sensors inside a tire )

"Marcel-G" <marcel-g@xs4all.nl> wrote in message
news:1a53e44a.0404190554.713f0a1c@posting.google.com...
> If a microcontroller can run permanently in running state some clock
> is running and the power consumption is higher then in sleep.
> So during running state it is usually not a problem from power
> consumption point of view to have  a watchdog running.
>
> I`m talking about a device which can be a year in sleep, used for a
> few minutes and sleep again for a long time.
>
> Marcel

In that case I'd be seriously tempted to store any state I need in
non-volatile memory, perhaps serial EEPROM or serial FLASH. Do a complete
reinitialisation on wakeup and go and see what was happening when the device
went to sleep.

Peter.

> A microcontroller is most susceptible at the parts which are at the
> outer side of the die ( usually I/O ports ). If an I/O register is
> changed for example from Input to output while it`s in sleep mode for
> an interrupt from that pin it never will wake up.

Hmmmm... if that's true, I suspect that based on closeness to the edge of
the die, the IO input buffer register is more susceptible than the
configuration register so you're more likely to get a spurious wakeup than
to have an input turned to an output?

> in an initialized state. In this condition the microcontroller can be
> affected by ESD, EMI which means the initialization can be corrupted
> -> there is a risk it does not wake up anymore.

If that is the ONLY thing you are worried about, then use an external
watchdog - when the wakeup stimulus arrives, it should start a delayed
one-shot which will generate a reset to the micro unless the micro
wakes up and does some positive action within [time interval].