[MPC5748G] Question about startup_MPC5748G.S file

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[MPC5748G] Question about startup_MPC5748G.S file

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kmh48301
Contributor IV

Hello.

I am working in "hello_world_mpc5748g" example project.

And I changed the "startup_MPC5748G.S" file in this example project.

Like this :

kmh48301_0-1611291921558.png

 

Original :  this startup code is making CTR register value 128

But I wanted to make CTR register value 127.

So, I changed the code like that.

 

The reason why I changed it is I need to reserve the memory address "0x4003_FFF0".

"Initialise SRAM ECC" part (I attatched) changed the value of address "0x4003_FFF0".

But I don't know the "Initialise SRAM ECC" part is for what..

 

So my question is 
1. Can I change the "Initialise SRAM ECC" part in Startup code? 

I worry some unexpected problem would be ocurred.

2. What does the "Initialise SRAM ECC" part in Startup code do? Please Explain more.

 

 

Thanks

Best regards

Phillip

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lukaszadrapa
NXP TechSupport
NXP TechSupport

Hi Phillip,

here you can find the explanation:

lukaszadrapa_0-1611332610836.png

It is possible to retain some SRAM content through reset but it depends which reset occurred.

Resets which destroy RAM content:
1. Power on Reset 2. Destructive reset 3. Long functional reset (with MBIST enabled)
Ram content is unchanged on:
1. Short functional reset 2. Long functional reset (MBIST disabled)

So, it is necessary to check the type of reset (see MC_RGM module). If it was reset which destroyed the RAM content, it is necessary to initialize whole SRAM. If that reset didn't destroy the RAM, you can skip initialization on desired area.

Regards,

Lukas

 

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kmh48301
Contributor IV

Thank you so much!!!!

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lukaszadrapa
NXP TechSupport
NXP TechSupport

Hi Phillip,

here you can find the explanation:

lukaszadrapa_0-1611332610836.png

It is possible to retain some SRAM content through reset but it depends which reset occurred.

Resets which destroy RAM content:
1. Power on Reset 2. Destructive reset 3. Long functional reset (with MBIST enabled)
Ram content is unchanged on:
1. Short functional reset 2. Long functional reset (MBIST disabled)

So, it is necessary to check the type of reset (see MC_RGM module). If it was reset which destroyed the RAM content, it is necessary to initialize whole SRAM. If that reset didn't destroy the RAM, you can skip initialization on desired area.

Regards,

Lukas