3.3 V-- Battery-Back up for Static RAM in RCM3010?

Started by pra_shant3000 May 11, 2005
Hi Friends,

Is there any 3.3V battery backup facility for SRAM of RCM3010?
I think, 3.3V battery backup is only available for RTC, in RCM3010.
I need a RCM module with battery backed facility for SRAM.
Please, tell me ,such RCM modules with 3.3V battery backup for
both SRAM & RTC. Also tell me ,what extra hardware & control signals
are required to give a battery back up for SRAM & RTC.

With regards,

Prashant.



At 06:06 PM 5/11/2005 +0000, you wrote:
>
>Hi Friends,
>
> Is there any 3.3V battery backup facility for SRAM of RCM3010?
>I think, 3.3V battery backup is only available for RTC, in RCM3010.
>I need a RCM module with battery backed facility for SRAM.
> Please, tell me ,such RCM modules with 3.3V battery backup for
>both SRAM & RTC. Also tell me ,what extra hardware & control signals
>are required to give a battery back up for SRAM & RTC.

3010 has battery backed ram, I use it. Only hardware you need is a 3v
battery, holder, and 1.4K resistor, hooked to the VBAT_EXT pin on the core
module.


Mike van Meeteren wrote:
> At 06:06 PM 5/11/2005 +0000, you wrote:
> >
> >Hi Friends,
> >
> > Is there any 3.3V battery backup facility for SRAM of RCM3010?
> >I think, 3.3V battery backup is only available for RTC, in RCM3010.
> >I need a RCM module with battery backed facility for SRAM.
> > Please, tell me ,such RCM modules with 3.3V battery backup for
> >both SRAM & RTC. Also tell me ,what extra hardware & control signals
> >are required to give a battery back up for SRAM & RTC.
>
> 3010 has battery backed ram, I use it. Only hardware you need is a 3v
> battery, holder, and 1.4K resistor, hooked to the VBAT_EXT pin on the core
> module.
>

What's the 1.4K resistor for?



At 07:17 AM 5/12/2005 +1000, you wrote:
>What's the 1.4K resistor for?

Not sure, but they put one on the development boards. I've put one on
every board I've ever designed. I suppose it could be to current limit it,
I don't know. It makes a convenient place to measure current draw though
(although you do need a GOOD multimeter for that).

-Mike


I think it is good design practice with lithium batteries to always have a
current limit resistor in series as close to the battery as possible. That
way a board short is less likely to result in exploding lithium. I know
most lithium batteries have sufficient internal impedance to stop this
happening, but I have worked with some hi energy types that could self
ignite. Once burning these things can combust for hours, even under water!

-----Original Message-----
From: rabbit-semi@rabb... [mailto:rabbit-semi@rabb...] On
Behalf Of Mike van Meeteren
Sent: Thursday, 12 May 2005 9:32 a.m.
To: rabbit-semi@rabb...
Subject: Re: [rabbit-semi] 3.3 V-- Battery-Back up for Static RAM in
RCM3010?

At 07:17 AM 5/12/2005 +1000, you wrote:
>What's the 1.4K resistor for?

Not sure, but they put one on the development boards. I've put one on every
board I've ever designed. I suppose it could be to current limit it, I
don't know. It makes a convenient place to measure current draw though
(although you do need a GOOD multimeter for that).

-Mike

Yahoo! Groups Links
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Mike van Meeteren wrote:

> At 07:17 AM 5/12/2005 +1000, you wrote:
> >What's the 1.4K resistor for?
>
> Not sure, but they put one on the development boards. I've put one on
> every board I've ever designed. I suppose it could be to current limit it,
> I don't know. It makes a convenient place to measure current draw though
> (although you do need a GOOD multimeter for that).
>
> -Mike
>

In other words it's not really needed.
I've used a 100R resistor for current limiting in the case where the RCM
fails and shorts the battery. 1.4k seems high.


Hi All,

I have been following this subject with interest. I have been trying to
get the SRAM on RCM3300 to retain its content when the power is
switched off.

I am using RCM3300 prototyping board for development, which already has
a battery connected to the VBAT-EXT pin on the RCM3300 module. The
battery is 3.0 V.

In my software I used protected keyword when declaring variables that I
want to back-up. However, the SRAM seems to lose its content when I
unplugged the power. The RTC seems to retain the time, when power is
removed.

I attached sample test code below. What did I do wrong?

********************************************************************

#use rcm33xx.lib

protected char nvram[16];
protected char ch;

main()
{
unsigned long Clock;
struct tm Time;

brdInit();

_sysIsSoftReset();

printf( "Content of nvram after power-up: %s\n", nvram );
printf( "Content ch after power-up: %d\n", ch );

ch = 123;
strcpy( nvram, "New content");

printf( "Content of nvram: %s\n", nvram );
printf( "Content of ch: %d\n", ch );

while(1){
costate{
// wait 1 second before displaying time
waitfor( DelaySec( 1 ) ) ;

Clock = read_rtc();
mktm( &Time, Clock );

printf( "Time: %02d:%02d:%02d\n", Time.tm_hour,
Time.tm_min, Time.tm_sec );
}
}
}

**************************************************************** --- Mike van Meeteren <mike@mike...> wrote:
> At 06:06 PM 5/11/2005 +0000, you wrote:
> >
> >Hi Friends,
> >
> > Is there any 3.3V battery backup facility for SRAM of RCM3010?
> >I think, 3.3V battery backup is only available for RTC, in RCM3010.
> >I need a RCM module with battery backed facility for SRAM.
> > Please, tell me ,such RCM modules with 3.3V battery backup for
> >both SRAM & RTC. Also tell me ,what extra hardware & control
> signals
> >are required to give a battery back up for SRAM & RTC.
>
> 3010 has battery backed ram, I use it. Only hardware you need is a
> 3v
> battery, holder, and 1.4K resistor, hooked to the VBAT_EXT pin on the
> core
> module.
Yahoo! Mail
Stay connected, organized, and protected. Take the tour:
http://tour.mail.yahoo.com/mailtour.html


Andy,

What measurement do you get for the voltage on the RCM3300 module from
the battery when the power is switched off? Is your battery connected
directly to the RCM3300 vbatt pin or via a resistor?

Andy wrote:

> Hi All,
>
> I have been following this subject with interest. I have been trying to
> get the SRAM on RCM3300 to retain its content when the power is
> switched off.
>
> I am using RCM3300 prototyping board for development, which already has
> a battery connected to the VBAT-EXT pin on the RCM3300 module. The
> battery is 3.0 V.
>
> In my software I used protected keyword when declaring variables that I
> want to back-up. However, the SRAM seems to lose its content when I
> unplugged the power. The RTC seems to retain the time, when power is
> removed.
>
> I attached sample test code below. What did I do wrong?
>
> ********************************************************************
>
> #use rcm33xx.lib
>
> protected char nvram[16];
> protected char ch;
>
> main()
> {
> unsigned long Clock;
> struct tm Time;
>
> brdInit();
>
> _sysIsSoftReset();
>
> printf( "Content of nvram after power-up: %s\n", nvram );
> printf( "Content ch after power-up: %d\n", ch );
>
> ch = 123;
> strcpy( nvram, "New content");
>
> printf( "Content of nvram: %s\n", nvram );
> printf( "Content of ch: %d\n", ch );
>
> while(1){
> costate{
> // wait 1 second before displaying time
> waitfor( DelaySec( 1 ) ) ;
>
> Clock = read_rtc();
> mktm( &Time, Clock );
>
> printf( "Time: %02d:%02d:%02d\n", Time.tm_hour,
> Time.tm_min, Time.tm_sec );
> }
> }
> }
>
> **************************************************************** > --- Mike van Meeteren <mike@mike...> wrote:
>
>>At 06:06 PM 5/11/2005 +0000, you wrote:
>> >
>> >Hi Friends,
>> >
>> > Is there any 3.3V battery backup facility for SRAM of RCM3010?
>> >I think, 3.3V battery backup is only available for RTC, in RCM3010.
>> >I need a RCM module with battery backed facility for SRAM.
>> > Please, tell me ,such RCM modules with 3.3V battery backup for
>> >both SRAM & RTC. Also tell me ,what extra hardware & control
>>signals
>> >are required to give a battery back up for SRAM & RTC.
>>
>>3010 has battery backed ram, I use it. Only hardware you need is a
>>3v
>>battery, holder, and 1.4K resistor, hooked to the VBAT_EXT pin on the
>>core
>>module.
>>
> >
>
> Yahoo! Mail
> Stay connected, organized, and protected. Take the tour:
> http://tour.mail.yahoo.com/mailtour.html >
>
> Yahoo! Groups Links >



Hi Geoff,

The voltage across VBAT_EXT & GND is 3.003V when no power is connected. I am using Rabbit RCM3300 prototyping board. Looking at the schematic
http://www.zworld.com/documentation/schemat/090-0188.pdf, the battery
is connected via a 1.3K resistor.

Regards,
Andy

--- Geoff Swan <gswan3@gswa...> wrote:
> Andy,
>
> What measurement do you get for the voltage on the RCM3300 module
> from
> the battery when the power is switched off? Is your battery connected
>
> directly to the RCM3300 vbatt pin or via a resistor?
>
> Andy wrote:
>
> > Hi All,
> >
> > I have been following this subject with interest. I have been
> trying to
> > get the SRAM on RCM3300 to retain its content when the power is
> > switched off.
> >
> > I am using RCM3300 prototyping board for development, which already
> has
> > a battery connected to the VBAT-EXT pin on the RCM3300 module. The
> > battery is 3.0 V.
> >
> > In my software I used protected keyword when declaring variables
> that I
> > want to back-up. However, the SRAM seems to lose its content when I
> > unplugged the power. The RTC seems to retain the time, when power
> is
> > removed.
> >
> > I attached sample test code below. What did I do wrong?
> >
> >
> ********************************************************************
> >
> > #use rcm33xx.lib
> >
> > protected char nvram[16];
> > protected char ch;
> >
> > main()
> > {
> > unsigned long Clock;
> > struct tm Time;
> >
> > brdInit();
> >
> > _sysIsSoftReset();
> >
> > printf( "Content of nvram after power-up: %s\n", nvram );
> > printf( "Content ch after power-up: %d\n", ch );
> >
> > ch = 123;
> > strcpy( nvram, "New content");
> >
> > printf( "Content of nvram: %s\n", nvram );
> > printf( "Content of ch: %d\n", ch );
> >
> > while(1){
> > costate{
> > // wait 1 second before displaying time
> > waitfor( DelaySec( 1 ) ) ;
> >
> > Clock = read_rtc();
> > mktm( &Time, Clock );
> >
> > printf( "Time: %02d:%02d:%02d\n", Time.tm_hour,
> > Time.tm_min, Time.tm_sec );
> > }
> > }
> > }
> >
> > ****************************************************************
> >
> >
> > --- Mike van Meeteren <mike@mike...> wrote:
> >
> >>At 06:06 PM 5/11/2005 +0000, you wrote:
> >> >
> >> >Hi Friends,
> >> >
> >> > Is there any 3.3V battery backup facility for SRAM of RCM3010?
> >> >I think, 3.3V battery backup is only available for RTC, in
> RCM3010.
> >> >I need a RCM module with battery backed facility for SRAM.
> >> > Please, tell me ,such RCM modules with 3.3V battery backup for
> >> >both SRAM & RTC. Also tell me ,what extra hardware & control
> >>signals
> >> >are required to give a battery back up for SRAM & RTC.
> >>
> >>3010 has battery backed ram, I use it. Only hardware you need is a
> >>3v
> >>battery, holder, and 1.4K resistor, hooked to the VBAT_EXT pin on
> the
> >>core
> >>module.
> >>
> >>
> >
> >
> >
> >
> > Yahoo! Mail
> > Stay connected, organized, and protected. Take the tour:
> > http://tour.mail.yahoo.com/mailtour.html
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>
Discover Yahoo!
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I don't think its the battery. Try the program you wrote without the
"protected" statement.

char nvram[16];
char ch;

-----Original Message-----
From: rabbit-semi@rabb... [mailto:rabbit-semi@rabb...] On
Behalf Of Andy
Sent: Thursday, 12 May 2005 10:02 p.m.
To: rabbit-semi@rabb...
Subject: Re: [rabbit-semi] 3.3 V-- Battery-Back up for Static RAM in
RCM3010?

Hi Geoff,

The voltage across VBAT_EXT & GND is 3.003V when no power is connected. I am using Rabbit RCM3300 prototyping board. Looking at the schematic
http://www.zworld.com/documentation/schemat/090-0188.pdf, the battery is
connected via a 1.3K resistor.

Regards,
Andy

--- Geoff Swan <gswan3@gswa...> wrote:
> Andy,
>
> What measurement do you get for the voltage on the RCM3300 module from
> the battery when the power is switched off? Is your battery connected
>
> directly to the RCM3300 vbatt pin or via a resistor?
>
> Andy wrote:
>
> > Hi All,
> >
> > I have been following this subject with interest. I have been
> trying to
> > get the SRAM on RCM3300 to retain its content when the power is
> > switched off.
> >
> > I am using RCM3300 prototyping board for development, which already
> has
> > a battery connected to the VBAT-EXT pin on the RCM3300 module. The
> > battery is 3.0 V.
> >
> > In my software I used protected keyword when declaring variables
> that I
> > want to back-up. However, the SRAM seems to lose its content when I
> > unplugged the power. The RTC seems to retain the time, when power
> is
> > removed.
> >
> > I attached sample test code below. What did I do wrong?
> >
> >
> ********************************************************************
> >
> > #use rcm33xx.lib
> >
> > protected char nvram[16];
> > protected char ch;
> >
> > main()
> > {
> > unsigned long Clock;
> > struct tm Time;
> >
> > brdInit();
> >
> > _sysIsSoftReset();
> >
> > printf( "Content of nvram after power-up: %s\n", nvram );
> > printf( "Content ch after power-up: %d\n", ch );
> >
> > ch = 123;
> > strcpy( nvram, "New content");
> >
> > printf( "Content of nvram: %s\n", nvram );
> > printf( "Content of ch: %d\n", ch );
> >
> > while(1){
> > costate{
> > // wait 1 second before displaying time
> > waitfor( DelaySec( 1 ) ) ;
> >
> > Clock = read_rtc();
> > mktm( &Time, Clock );
> >
> > printf( "Time: %02d:%02d:%02d\n", Time.tm_hour,
> > Time.tm_min, Time.tm_sec );
> > }
> > }
> > }
> >
> > ****************************************************************
> >
> >
> > --- Mike van Meeteren <mike@mike...> wrote:
> >
> >>At 06:06 PM 5/11/2005 +0000, you wrote:
> >> >
> >> >Hi Friends,
> >> >
> >> > Is there any 3.3V battery backup facility for SRAM of RCM3010?
> >> >I think, 3.3V battery backup is only available for RTC, in
> RCM3010.
> >> >I need a RCM module with battery backed facility for SRAM.
> >> > Please, tell me ,such RCM modules with 3.3V battery backup for
> >> >both SRAM & RTC. Also tell me ,what extra hardware & control
> >>signals
> >> >are required to give a battery back up for SRAM & RTC.
> >>
> >>3010 has battery backed ram, I use it. Only hardware you need is a
> >>3v battery, holder, and 1.4K resistor, hooked to the VBAT_EXT pin on
> the
> >>core
> >>module.
> >>
> >>
> >
> >
> >
> >
> > Yahoo! Mail
> > Stay connected, organized, and protected. Take the tour:
> > http://tour.mail.yahoo.com/mailtour.html
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>
Discover Yahoo!
Get on-the-go sports scores, stock quotes, news and more. Check it out!
http://discover.yahoo.com/mobile.html
Yahoo! Groups Links
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