This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

[FAQ] F05 Flash: Why does the erase time vary from part to part?

Q: Why does the erase time vary from part to part? They are the same part number.  Is something wrong with some of the devices?

  • A:

    Refer to the flash timing information in the datasheet or data manual for your device.  This document provides information for expected erase and program times.

    The following answer refers to F05 flash technology (Which devices include F05 Flash?)

    The Flash erase/program operations are quite different from Flash-read or RAM read/write operations. They can not be counted as ‘fixed number’ of CPU cycles. This is due to the nature of flash process. The F05 erase operation has 4 steps as below:

    1. Pre-compact – makes sure no bits are in an over erased state.
    2. Clear – Programs all bits in the sector to 0.
    3. Erase – Sets all bits in the sector to 1 and
    4. Compaction - Corrects any “over-erased” (depleted) bits.

    The Erase operation is a dynamic operation - pulses are applied until the erase is complete or the maximum number of pulses is reached and the erase fails. Thus the amount of time it takes to erase will vary per attempt and per sector. It will change at different temperatures, and in addition it will also change with ‘the number of previous erase/program cycles’ (flash endurance). Hence, it will also change from part to part. The system related issues/parameters (supply voltage, ripple/noise etc) will be on top of this. This will change with temp as well as during the lifetime of the flash.

    In summary, the erase function of the different flash sectors is a highly dependable process. It depends on temperature, silicon age, number of previous erase steps, amount of flash used, etc. The erase operation will vary from chip to chip, but typically you will see a few seconds per sector to erase- see the datasheet for specifications.

    For more F05 related FAQs refer to [FAQ] F05 Flash: Frequently Asked Questions