RH850 Flash number of rewrites

Hello,

I have a question regarding the RH850 Flash number of rewrites:

Based on the RH850/F1KH, RH850/F1KM datasheet page 222 (3A.7.2) where I see the following sentence:

Note 1. The number of rewrites is the number of erasures for each block. When the number of rewrites is “n” (n = 125000), the device can be erased “n” times for each block. For example, when a block of 64 bytes is erased after 4 bytes of writing have been performed for different addresses 16 times, the number of rewrites is counted as 1. However, multiple writing to the same address is not possible with 1 erasure (overwriting prohibited).

Please could you clarify the followings:

1. When in the sentence is saying 4 bytes of writing in a block of 64 bytes means in 16 different address meaning 4 bytes per address it means I am writing 1 time 64 bytes or 16 times?

2. What about the erase after 4 bytes what that means ? After write a 4 bytes address I should erase once ?

Another question is retention policy of 250K number of rewrites in 3 years what that means ?

I really need to clarify as its' not clear what is the strategy to count as 1 write in the flash.

Thanks a lot,

Marcelo

Parents
  • Essentially what this explanation is trying to say is, the data-flash memory is erased in 64-byte blocks, a write to any 4-byte (1-word) address in this block (of which 4-bytes is the minimum write size) followed by an erase counts as one (1) write / erase cycle.

    The data-flash is designed to retain for 20yrs for the first 125K write / erase cycles.  After 125K, the guarantee is 3yrs, up to 250K write / erase cycles.

    A good EEPROM emulation strategy will wear-level the data, i.e. spread out the writes across multiple addresses.

    If your application is non-AUTOSAR / non-FuSa (i.e. QM), you can use the RH850 EEPROM emulation library (EEL) with the corresponding FDL.  For AUTOSAR and/or FuSa applications the recommendation would be to use the low-level MCAL driver (FLS) along with a 3rd party FEE.  Unfortunately Renesas does not offer the FEE module for RH850 devices.

    References:

    RV28F / RV40F DataFlash Usage

    RH850 - Data Flash Library (FDL) Manual - Software

    RH850 - Data Flash Library (FDL) - Software

    I would have pointed you to the European MyPages portal for the EEL but I understand this is going away in a few short weeks.  I don't know the alternative / new method of obtaining such a software package and documentation.

Reply
  • Essentially what this explanation is trying to say is, the data-flash memory is erased in 64-byte blocks, a write to any 4-byte (1-word) address in this block (of which 4-bytes is the minimum write size) followed by an erase counts as one (1) write / erase cycle.

    The data-flash is designed to retain for 20yrs for the first 125K write / erase cycles.  After 125K, the guarantee is 3yrs, up to 250K write / erase cycles.

    A good EEPROM emulation strategy will wear-level the data, i.e. spread out the writes across multiple addresses.

    If your application is non-AUTOSAR / non-FuSa (i.e. QM), you can use the RH850 EEPROM emulation library (EEL) with the corresponding FDL.  For AUTOSAR and/or FuSa applications the recommendation would be to use the low-level MCAL driver (FLS) along with a 3rd party FEE.  Unfortunately Renesas does not offer the FEE module for RH850 devices.

    References:

    RV28F / RV40F DataFlash Usage

    RH850 - Data Flash Library (FDL) Manual - Software

    RH850 - Data Flash Library (FDL) - Software

    I would have pointed you to the European MyPages portal for the EEL but I understand this is going away in a few short weeks.  I don't know the alternative / new method of obtaining such a software package and documentation.

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