MPC56xx C90FL Flash Recovery: In Case of Brownout during Flash Erase Operation
●The MPC56xx family of devices have internal nonvolatile flash memory that is used for code and data. Two types of flash modules have been implemented on the Freescale MPC56xx devices, the C90FL and the C90LC. The C90FL flash is optimized for large flash memory arrays, while the C90LC is optimized for smaller flash array configurations. Flash memory is designed to allow fast programming, but requires that a full block be erased at a time. Once programmed, the flash memory retains its programed state (nonvolatile) while powered off. In this technology, each cell in the flash memory array holds the value of one bit (either 0 for programmed or 1 for erased). This is a 2 level NOR flash implementation¹ and uses a single voltage threshold to determine if a bit is high or low. This insures maximum data retention to meet harsh automotive requirements. For even more protection against bit-flips, this technology implements Error Correction Coding (ECC) that is guaranteed to correct single bit errors and will identify any double-bit errors within the ECC code word (64-bit data bits plus 8 ECC parity bits). Due to ECC, it is possible to put the flash memory into a state where the ECC bits are invalid. This can occur if an erase operation is interrupted prior to completion.
●If a brownout occurs during an erase operation on the C90FL flash, the flash blocks being erased can be left in an indeterminate state (invalid ECC values). A brownout is defined as an accidental power loss or supply voltage drop or unexpected reset.
●This application note describes how to recover the C90FL flash block(s) that were left in illegal states by an interrupted erase, if such a brownout occurs.
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MPC56xx 、 MPC564xA 、 MPC564xL 、 MPC564xS 、 MPC5668G 、 MPC5668F 、 MPC567xF 、 MPC5676R |
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Application note & Design Guide |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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02 May 2012 |
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Rev. 1 |
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AN4521 |
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286 KB |
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