AnsweredAssumed Answered

Flash cache invalidate.

Question asked by Anatoly Odler on Jul 23, 2013
Latest reply on Aug 15, 2013 by Melissa A Hunter

Hi,

I'm developing for the K10 MCU, CD IDE 10.4, compiler GCC 4.7.3.

The MCU has one block of the Flash program memory, 512Kb overall, no EEPROM.

 

I have written a flash driver, which provides standard services, like read, write, erase sector, to the main application.

All these routines of the driver run from RAM. The driver was implemented according to the MK10DN512VMC10(R) reference manual,

all the flash commands and register operating code is similar to the C90TFS driver available from Freescale.

The additional thing I do in my writeLongWord() routine is verifying if the data has been written as expected by simply comparing the argument of value to be written

to the content on flash taken from the argument of destination address.

What I get is these two values aren't equal somehow, while the FTFL_FSTAT register indicates no errors.

The MCU's reference manual, 28.6 Initialization and application information, tells there's a need to invalidate flash cache by writing the PFB0CR[CINV_WAY] bits

of the Flash Memory Controller. I have added this operation to my sequence before each write, it solves the verification issue.

 

I'm using the security of the device by configuring the security FSEC bit and the backdoor key.

I'm trying to write something on flash, which is the part of a calibration process of the device I'm developing, and then I want to unsecure the device

by the backdoor key. The issue is that, when I try to unsecure the device by applying the key, the MCU resets with no response to the verify backdoor command.

The strange thing is, if I remove the invalidating sequence of the flash cache from the flash driver code and ignore the data verification, the unsecure command works properly!!!

My conclusion is that the invalidating the flash somehow affects the security commands of the flash module.

The strangest thing is, if I write the flash, reset the MCU by hard reset (voltage switch), and then try to unsecure it, it resets as well !!!!

 

What does really the invalidate command do? When I need to perform it (if ever)? How can I ensure the verification of the written data succeeds?

How the backdoor verify is affected by flash cache invalidation?

Please refer to the mentioned problems.

 

Thank you, Anatoly.

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