4 or 8 Megabyte addressable EEPROM memory space possibility with BS2 series ??

BYRON

I understand that it is a relatively simple matter to hook up 4 each 1024 MegaBit EEPROM chips (like 4 of the 24LC1025 EEPROM chips) to get a total addressable· EEPROM memory space of· 512 KBytes (half a MegaByte).·

My question is whether it is realistically possible to purchase and design-in ·EEPROM devices which will allow for 4 or, perferably, 8· MegaBytes of· addressable·EEPROM memory space.· What is the easiest and cheapest way to get that size of addressable EEPROM memory space?

Chris Savage

Byron,

If you were referring to chips such as 24LC32 or 24LC256 things would be much easier. The real problem is addressing. The largest number the BASIC Stamp can handle is 65535. You wouldn’t be able to directly address higher memory unless you created some really tricky code to handle it. For that much storage it is more recommended to use a Vinculum IC as a host controller with a serial interface to use USB Thumb Drives. Then you could easily get 4GB of storage if you like. Take care.

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Chris Savage
Parallax Tech Support

Mike Green

There are large (several MB) Flash EEPROM devices made by Atmel and others that use the SPI protocol (instead of the I2C protocol used by the EEPROM devices you've mentioned).· This is partly implemented with the SHIFTIN and SHIFTOUT statements.· These are sector addressable and have RAM buffers which simplify their use.· As Chris mentioned, the major problem is handling the multiple precision arithmetic necessary for addressing.· This is particularly difficult given the limited variable of the Stamps.· Chris's suggestion to use the Vinculum devices is a good one.

Tracy Allen

There's an article about using the Atmel dataflash at www.emesys.com/BS2flash.htm.
Also see www.atmel.com/products/DataFlash/
At present, you can buy up to 32 megabit (4 megabyte), the AT45DB321D, in an 8 pin soic or cason package. I don't think you can beat that for density.

I manage the addressing by working with fixed length records. Since each record occupies quite a few bytes, the numbers aren't too big. Working from the record number and a base address, the program calculates the page number and the offset on the page, also numbers that are not so big. But it is not the easiest memory to deal with, partly due to the size and the paging, but also due to the considerations of wear leveling and occasional page refresh. Also, the Stamp is not very fast, and you have to think of how you are going to access all that data. I don't know what yur application is, but if you plan to collect data and then transfer it through the serial port it can take a long time.

Another option is the host controller that Chris suggested, or the SDdataLogger that uses standard SD cards.

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Tracy Allen
www.emesystems.com

allanlane5

Which brings up the question of how fast you want to write these beasts. 56 KBit per second would take a long time to fill up 8 Megabytes -- like 20 minutes.