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Flash memory Vs SRAM

A46810
Intellectual 560 points


Hi

I am using the MSP430FG 4618, I have to save some data on the flash memory for permanent use. I am not sure how different is it from storing the data in  variables in the code. Would just moving the required data int the flash memory locations do the trick ? But then again I would have to use and assembly code together/

  • 0
    Guru 227245 points

    Flash write and SRAM write are two substantially different things.

    If writing to SRAM is like writing with crayon on a blackboard (which is auto-cleaned when the power is off), then writing to flash is rather like shooting the image of a letter into a paper - It will survive the power-off, but to write something different, you will need to take a fresh paper or else you can only add new holes.

    Back to the memory, you can write to SRAM at any time with full speed, yet on power-fail all is lost.
    when writing to flash, you can only write '0' into the flash cells and it takes some time. You cannot write a '1' bit when the cell already contains a '0'. To reset a single bit from 0 to 1, you have to clean the whole flashsegment, which takes whopping 30ms and sets a whole bunch of 512 bytes back to 0xff content.

    For storing small amounts of data, the MSPs contain the 'info mem' area, where each flash segment (that must be erased in a block) is only 128 or (on some MSPs) 64 bytes. Yet the programming of each byte and the erase process still takes the same amount of time.

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