RAM Chip for use in project

blutfort

I'm working on a project were I need to keep track of the value of an input on a small delta T.· 1 to 60 second intervals.· I'd like to confer with some of the guru's here about some best practices.

1.· I don't want to use an EEPROM as primary storage.· I will quickly deplete the # of write cycles.
2.· I want to store the data in a sort of volitale ram and periodically move it to EEPROM, possible on when volitle ram is almost full and when a brownout is detected.
3.· My best way to minimize stored data volume is to watch for a change of state on binary inputs and record the time that the state changes.· That way I know the status at whatever time interval I want!· The same can be considered for analog inputs.· If I only record when the value changes by a minimium delta value I programatically know the value at any time in between.· (within the resolution limits ste as my delta).

What would be a good chip to use for the volitle ram?
Is this a best practice way of doing this?

Thanks!

K de Jong

Look at clock chips. Some have spare volatile RAM which will be non-volatile if you prvide a backup battery or capacitor.

DS1302 has 31 bytes RAM free.
PCF8583 (I2C-bus) has over 200 bytes.

You then have the RAM _and_ a real time clock, which is handy in datalogging applications .

Succes,

Klaus

Tracy Allen

I use the Atmel AT45DBxxx serial dataflash. These chips have RAM buffers of 528 bytes in addition to flash memory of 256Kbytes or more. You can fill up the RAM buffer and then transfer it with one instruction to the next free flash page.

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Tracy Allen
www.emesystems.com

Don

blutfort said...
What would be a good chip to use for the volitle ram?

I used the old MCM6810 128x8 static RAM in a design several years ago.· Worked great.· Of course, you'll have to add your own address latches and probably data latches as well.· Here is a link to a page describing the 12.5KW diesel generator controller that I built (includes schematics and code): http://www.kinzers.com/don/GenSet

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Don Kinzer



Post Edited (Don) : 1/10/2005 5:54:35 AM GMT

SPENCE

Solutions cubed has a serial io ram which i think is 8 k expandable to 32k. It is static and does use external power.
A back up battery would hold you data for a log time and you could use several of the modules together.
73
spence
k4kep

achilles03

If I understood your post correctly, you stated you would be·sampling·data between once a second to once a minute.· I don't think you would be exhausting the write cycles on any eeprom for with that sample rate.· Let's say 100,000 write cycle max per address with an 8kbyte chip, with 1 sample per second... it would take 26 years to write to each address 100,000 times.· If you're still concerned,·there's higher write-cycle eeproms out there.

I might reconsider an eeprom.

Dave