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Hi All

I have decided to use an LPC2103 for a small project with date, time and a few battery backed up variables.

So I just did some initial checks that the battery backup consumption is as stated (which is is ca. 7uA) and that the registers are all as stated.

Since there are only a few variables that need to be battery backed up I though that any unused alarms would be a suitable location for them - probably the alarm functions will not be required.

During tests I found that there is a block of addresses between the time registers and the alarm registers which is not documented. This address range is 0xe0024040 to 0xe002405c inclusive. This is what I found during practical tests of reading and writing these addresses and also the impact of resets and battery backed up periods:

0xe0024040 has a fixed value of 0x0000007 - can not be changed

0xe0024044 can be written and read - all 32 bits - and the value is retailed after a reset and a period of battery backup
0xe0024048 dito
0xe002404c dito

0xe0024050 fixed value of 0x00000000 read only
0xe0024054 dito
0xe0024058 dito
0xe002405c dito

There are a total of 50 alarm bits which could be used for battery backed up storage but possibly a further 96 bits between 0xe0024044..0xe002404c.

Does anyone know anything about these undocumented locations? This is useful space if it can be reliably used, but can it??? Or were my tests somehow just luck???? (I did remove RS232 and JTAG connections to ensure that there was no invisible supply path somewhere...)

Cheers

Mark

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--- In l...@yahoogroups.com, "mjbcswitzerland" wrote:

> 0xe0024040 has a fixed value of 0x0000007 - can not be changed
>
> 0xe0024044 can be written and read - all 32 bits - and the value is retailed after a reset and a period of battery backup
> 0xe0024048 dito
> 0xe002404c dito
>
> 0xe0024050 fixed value of 0x00000000 read only
> 0xe0024054 dito
> 0xe0024058 dito
> 0xe002405c dito
>

Of the regs you mention, only 24044..2404c can store data (based on your tests) and they are fully documented in the User Manual section 6.14. They are intended for user storage.

Richard

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(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )

Thanks Richard

I was using the user manual Rev. 3 which didn't have this new section in it (after downloading the latest manual it is there as you say). I see that these registers are only available from chip rev. A, which I obviously have on my eval board...

This is in any case good news since the 50 bits were a bit tight and would have required some manipulation to get the bytes to fit...

Regards

Mark
> Of the regs you mention, only 24044..2404c can store data (based on your tests) and they are fully documented in the User Manual section 6.14. They are intended for user storage.
>
> Richard
>

------------------------------------



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Not exactly the same topic but still RTC related.

I am wondering what is the difference between the following count increment interrupts?
- day of week
- day of month
- day of year

I would expect that these three counters would always increment at exactly the same time, so why are there three possible interrupt triggers? I suppose that only one of them will need to be used(?)

Regards

Mark

> > Of the regs you mention, only 24044..2404c can store data (based on your tests) and they are fully documented in the User Manual section 6.14. They are intended for user storage.
> >
> > Richard
>

------------------------------------



(You need to be a member of lpc2000 -- send a blank email to lpc2000-subscribe@yahoogroups.com )

--- In l...@yahoogroups.com, "mjbcswitzerland" wrote:
>
> Thanks Richard
>
> I was using the user manual Rev. 3 which didn't have this new section in it (after downloading the latest manual it is there as you say). I see that these registers are only available from chip rev. A, which I obviously have on my eval board...
>
> This is in any case good news since the 50 bits were a bit tight and would have required some manipulation to get the bytes to fit...
>
> Regards
>
> Mark
I believe there are 'access' restrictions on the locations as well. I didn't check but on some variants, you must address them as 32 bit words only. No byte or short access allowed. You should check...

Richard

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