Q:Help with Microcontroller selction

I think, you can dig into the pile of PIC microcontrollers to see if any of those matches your specification.

Karthik Balaguru

Easier if you can settle for 8K

Sure there is, at least for some AVRs. You can run it in power saving mode with the RTC clock running. You should copy critical SRAM data into EEPROM anyway. Battery SRAMs are for lazy designers.

Hi,

thank you, will have a look.

Andreas

Hi,

The application will have to store data which can get more and more in time (musical allpiance). So 8k is the adsolut minimum.

Well, I need the SRAM for storing application data and that data can grow by input of the user. Storage (SD or other cards) I dont have so I need to hold the data in battery buffered SRAM since I have a power supply which can (of course) be switched off. Thats why I use byttery back up.

Thanks,

Andreas

There are some high end AVR that will work for you, with 8K SRAM and

2K EEPROM.

Unless you have a big battery, SRAM will kill it quickly. EEPROM can store data indefinitely. Any uC running SRAM will need a few mA at least. AVR, for example, can wait for RTC interrupt with less than

100uA, if you design it right. External EEPROM or FLASH is available as well.

That is a lot of RAM in a 8 bit, and battery backed is even rarer, so you have moved into a supply desert.

Better might be to look at external DataFLASH, or Ramtron FRAM or one of their processor companions : RTC + FRAM in one package. That gives you a scalable storage solution, fast and low power (FRAM does not even need a battery), and leaves the Core selection much simpler.

Hi!

linnix wrote on 19/01/08 19:53 MET:

Beware of the fact that EEPROMs can not be erase indefinitely, there's a limit of how often each erase-block can be erased.

An EEPROM with 100.000 erase cycles, the worth-case scenario of a full erase every second gives you a chip lifetime of 1.15 days.

So it all depends on how much data you are storing and how often each erase-block is being reprogrammed.

--
MfG / Regards
Friedrich Lobenstock

I am not saying that you should stream data into EEPROM directly. Before going into power down or standy mode, copy critical data from SRAM to EEPROM.

consider the Ultra low Power External SRAM by AMI, for instance the

32K x 8 bit serial SRAM (about 50 cents)

it only requires 200nA to retain memory so battery backup shouldn't be a problem

the also have megabyte parallel devices

Wow - SPI SRAM. I thought that had long since vanished off the planet, I see it came from NanoAmp Solutions, Inc

-jg

linnix wrote on 20/01/08 03:48 MET:

Agreed, I just wanted to point out if using EEPROM you very well have to take your write/erase pattern into account when calculating the max. obtainable life span.

--
MfG / Regards
Friedrich Lobenstock

Look at

They have several development systems that should suit your needs. The software is great. C/C++ and RTOS

george

There will soon be an ATmega1284P with

128kB Flash 16 kB SRAM Power Down current = 0,6uA with 32 kHz clock enabled. When you are only running the RTC, you can enable the CPU clock divider to run at low speed. At ~32 kHz the interrupt to run the RTC date/time keeping will add about 0,1uA to the average power consumption.

What you need is an power management circuit which will automatically switch over to the battery when the mains disappears. Maybe this is two diodes...

--
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB

Hi Ulf,

This sounds like the device I need!

16kByte is enough and all included is so cool. Do you know when it will be on the market?

Thanks, Andreas

"Andreas Schweiger" skrev i meddelandet news:4795e7bc$0$25381$ snipped-for-privacy@newsspool4.arcor-online.net...

There is internal silicon available, but I do not know the status. Be friendly with your local Atmel contact!

--
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB

meddelandetnews:4795e7bc$0$25381$ snipped-for-privacy@newsspool4.arcor-online.net...

Do you know where I can get the die layout (and samples) for ATmega169PV? I can't get any response from my local Atmel contact. May be I should move to Norway!

FWIW atmel is extremely optimisitic concerning new silicon, SAM7L, xmegaAVR are good examples, think another 6-12 months for samples and

2 years for production quantities, but you never know they could surprise you

FWIW atmel is extremely optimisitic concerning new silicon, SAM7L, xmegaAVR are good examples, think another 6-12 months for samples and

2 years for production quantities, but you never know they could surprise you

==> That is the charm with silicon, you know when you get next rev of the silicon but you do not know if that silicon works or not, and once in production you do not know if the next batch is going to yield or not. I never promise any dates, I just give "best case" availability.

--
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may not be shared by my employer Atmel Nordic AB