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MSP430F4794 flash mass erase max time?

da
Expert 2780 points
Other Parts Discussed in Thread: MSP430F4794
1.
The data sheet of the MSP430F4794 for Mass erase Time, does not have a MAX value.
I want to know the MAX value.

2.
Do not erase the Flash, when writing, but I think that it is as follows, do you have there?
before: write: after
0xFF -> (0xF0) -> 0xF0
0xF0 -> (0x0F) -> 0x00

Do not perform the erase the Flash, about being the writing, or not a problem occurs?
  • 0
    TI__Guru 68116 points

    Hi da,

    1. Are you referring to the value for tCMErast "cumulative mass erase time" in the datasheet? There is no max value. You just have to make sure you use a longer erase than the min value, but there is no max you can erase as long as you want. Similarly, for the cumulative program time tCPT, there is only a max value and no min value - you in that case have to simply ensure you stay below the cumulative program time for the whole block.

    Or did you mean, tMASS ERASE mass erase time, which only has a typical value. This only has one value because it is in terms of tFTG cycles, which are hard-wired into the flash controllers state machine - so you can't even affect that (it's part of the hardware). The only thing you can affect is the fFTG frequency - you need to make sure that stays in the fFTG specified min-max range. You also affect how many writes in a block occur before an erase and this affects cumulative program time, so that is why this is also specified.

    2.  You are asking, if you have a byte 0xFF (fully erased), and you write 0xF0 to it, you'll get 0xF0. And then if you do another write (over-programming) of 0x0F without an erase in-between, you should see 0x00 and would you have any problem because there is no erase in-between? The answer is that yes, you would end up with 0x00 after these two operations as you've described. For potential issues, it is listed in the app note   section 3.3 says:

    "The same 16-bit flash word cannot be programmed more than twice before the next erase cycle. Writing to one 16-bit word with two byte-wise programming cycles counts as two programming cycles. Single-bit overprogramming is possible only once, if the flash cell previously has been programmed 16-bit word wise."

    The same section also talks about the cumulative programming time and how you also need to take precautions not to violate that when you do this as well.

    Please see the application note for much more detailed information about cumulative program time and over-programming. I think it should answer a lot of your questions about flash requirements, endurance, and reliability. It has a great explanation of what cumulative program time means so you can make sure you do not violate the spec.

    Regards,

    Katie

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