Erasing EEPROM

agentile

I am working on a data-recording program, wherein the BS2 records time and temperature at five minute intervals.· At each interval the values for time and temp are stored in EEPROM.· I have had no trouble recording values to EEPROM.· I ran the system as a test, recording once a minute for two hours.· But now when I do a memory dump into hyperterminal, I get not just my new data, but a lot of old data that I don't want.· I had assumed that all the EEPROM would be set to 0 (or 255) upon loading a program.· But apparently this is not the case.· Is there an easy way to erase all my old data from EEPROM?

Thanks,
agentile

Newzed

Agentile, what EEPROM are you using?· Some overwrite when you set the address to 0, others require an erase routine.

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Sid Weaver
NEW! 4 MB EEPROM

http://hometown.aol.com/newzed/page4.html
·

agentile

Sid,

· I don't know exactly what type of EEPROM is on the stamp, but I am using the memory on the stamp.··I wrote a program which places 255 in each of the first 1500·memory locations.· This works, but I was hoping that there would be an easier way.· If you know of one, please let me know.



thanks,

agentile

Gadgetman

When you download a program to the Stamp it only writes to the locations SUPPOSED to contain either PROGRAM or predefined DATA, all other locations are left as they were.
I believe this was to increase the speed of the download.

If you want to erase every location, use DATA statements to overwrite the locations with '0'

Andy Lindsay (Parallax)

The command:

DATA 0 (2048)

will overwrite the BASIC Stamp's EEPROM with zeros. A separate program can then be loaded into memory for the datalogging.

Another way to deal with the problem is to write a unique value to the address that immediately follows the last address of valid data in EEPROM. For example, if you only plan on storing values from 0 to 127, a DO...LOOP or IF...THEN statement can be used to check for the "end of data" value before reading the next value. Here is a reading example:

index VAR Word
value VAR Byte

DO UNTIL value = 128

READ index, value
DEBUG ? value
index = index + 1

LOOP

END

Here is the writing example:

index VAR Word
value VAR Byte

DO UNTIL value = 128

DEBUG "Enter value: ", CR
DEBUGIN DEC value
WRITE index, value
index = index + 1

LOOP

END

allanlane5

Neat syntax, Andy. I assume the 'Data 0 (2048)' command will erase the code itself, too.

Oops, just tried it, apparently it is a compiler directive -- it HAS no code associated with it. Very nice.