mpc5744p NO_INIT RAM

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mpc5744p NO_INIT RAM

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huilongpeng
Contributor II

Hello,

 I want to implememt the following function:

When ECU in application, ECU writes some data in RAM ,the specified written RAM couldn't be cleared during the  software,not power on reset, and then ECU can read the exact data out. 

Thank you and best regards.

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davidtosenovjan
NXP TechSupport
NXP TechSupport

You can omit SRAM initialization for Functional reset sources. When a 'functional' reset event occurs, a
partial reset sequence is applied to the chip starting from PHASE1[FUNC], keeping the system memory
content preserved.

After reset, investigate content of MC_RGM_DES and MC_RGM_FES to know the reason of reset and based on that you can partially skip SRAM initialization.

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davidtosenovjan
NXP TechSupport
NXP TechSupport

You can omit SRAM initialization for Functional reset sources. When a 'functional' reset event occurs, a
partial reset sequence is applied to the chip starting from PHASE1[FUNC], keeping the system memory
content preserved.

After reset, investigate content of MC_RGM_DES and MC_RGM_FES to know the reason of reset and based on that you can partially skip SRAM initialization.

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yanronglu
Contributor II

HI,David:

I've already reset the function, but ram is still zero.

The following is the state of the reset.

pastedImage_1.png

pastedImage_2.png

pastedImage_4.png

The project is an additional variable in the FCCU in the example program.

pastedImage_3.png

    Can you help me see what went wrong?

Thanks.

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petervlna
NXP TechSupport
NXP TechSupport

Hi,

Well, from your English it is not possible to distinguish what you want to achieve.

Do you want to preserve RAM content trough reset or ...?

Peter

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huilongpeng
Contributor II

Hi,Peter

    I mean ram will not initialize to 0 after reset.

Thanks.

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Ray_V
Contributor V

set the attribute when you declare the variable to be placed in the noinit section.

For Example:

__attribute__ ((section("." noinit))) int MyVariable;

Peter Vlna are you saying there is a way to make it not initialize a variable for a particular reset but initialize it for other resets?

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petervlna
NXP TechSupport
NXP TechSupport

After which reset?

Power on Reset

Destructive reset

Long functional reset

Short functional reset

External long reset?

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huilongpeng
Contributor II

dhaval can you please help for this .

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