Compiler/TM4C1294KCPDT: preserve some RAM variables from being initialised to 0 at reset

Ping Wang

Tool/software: TI C/C++ Compiler

Hi, All

I need some RAM variable values to be kept from initlised to 0, ideally at a fixed location, it seems some processor is able to do this use # pragma NOINIT together with #pragma location. I tried but it seems the variable is ignored.

My questions are:

- is it possible with the processor I am using.

- if so, tell me the procedure please, do /i need to change the linker file?

Thanks in advance!

Ping

over 9 years ago

0 Keith Barkley over 9 years ago

Guru 44035 points

Do need them to be persistent or just not initialized? RAM will lose its contents on Power down.

0 George Mock over 9 years ago

TI__Guru**** 253590 points

Ping Wang said:
is it possible with the processor I am using.

We compiler experts lack the knowledge to answer that question.

Ping Wang said:
do /i need to change the linker file?

No.

Ping Wang said:
I tried but it seems the variable is ignored.

What do you see that leads you to this conclusion? Exactly how do you see it?

Thanks and regards,

-George

0 Ping Wang over 9 years ago in reply to George Mock

Intellectual 330 points

Hi, George

Thanks for reply, the following lines are my definition for a global variable called table, I intend to keep its value during reset and ideally at a fixed location too.

#pragma NOINIT (table)
uint32_t table;

When I run the whole my program in debug mode, the table is identified as a unknown varaible.

Regards!

Ping

0 Ping Wang over 9 years ago in reply to Keith Barkley

Intellectual 330 points

Hi, Keith

Thanks for reply, I only need them to be kept between resets, don't mind lose them after power cycle.

Any suggestion?

Ping

0 Keith Barkley over 9 years ago in reply to Ping Wang

Guru 44035 points

How are you doing the reset?

Are you using C++?

0 Ping Wang over 9 years ago in reply to Keith Barkley

Intellectual 330 points

hi, soft reset, by calling SysCtlReset().
Intend to have some thing kept between bootloader and application, probably need to use EEPROM.

I am using C.

0 George Mock over 9 years ago in reply to Ping Wang

TI__Guru**** 253590 points

Ping Wang said:

#pragma NOINIT (table)
uint32_t table;

When I run the whole my program in debug mode, the table is identified as a unknown varaible.

Does your program ever make use of this variable?

Thanks and regards,

-George

0 Ping Wang over 9 years ago in reply to George Mock

Intellectual 330 points

Hi, George

Thanks for remind, I wasn't using the variable initially. Now I give it a value, and it is recognised. Seems promising. Need to try whether it will kept the value between reset.

Regards!

Ping

0 Ping Wang over 9 years ago in reply to George Mock

Intellectual 330 points

Hi, George
Thanks, I get it working now, the following lines will keep the variable table in specified location and preserve its value from reset.

#pragma NOINIT (table)
#pragma location = 0x20000000
uint32_t table;

Ping

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Compiler/TM4C1294KCPDT: preserve some RAM variables from being initialised to 0 at reset