CodeWarrior Development Tools中的主题 How to set a NO-INIT var in C startup runtime?

How to set a NO-INIT var in C startup runtime?

w_tension — Fri, 12 Aug 2016 06:21:25 GMT

I konw I can edit *.PRM file to do this.

Is there a way like ARM compiler using "__no_init" command?

Re: How to set a NO-INIT var in C startup runtime?

ZhangJennie — Fri, 12 Aug 2016 07:09:22 GMT

Hi,

Thank you for posting your questions.

We can't do this for a specific variable but we can do it for a section. I suggest you use NO_INIT qualifier to the RAM section that you don't want be initialized.

NO_INIT: used for address ranges where read/write accesses are allowed. The linker does not initialize memory area defined with this qualifier at application startup. This is useful if your target has a battery-buffered RAM or to speed up application startup.

For example:

///////////////////////

SECTIONS

ROM = READ_ONLY 0x1000 SIZE 0x2000;

CLOCK = NO_INIT 0xFF00 TO 0xFFFF;

RAM = READ_WRITE 0x3000 TO 0x3EFF;

Page0 = PAGED 0x4000 TO 0x4FFF;

Page1 = PAGED 0x4000 TO 0x4FFF;

END

/////////////////////////

The CLOCK section is a READ_WRITE memory area. It starts at address 0xFF00 and ends at 0xFFFF (size = 100 bytes). Variables allocated in this segment are not initialized at application startup.

Does this answer your questions?

Have a great day,
Jennie Zhang

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Re: How to set a NO-INIT var in C startup runtime?

mihir_rajput — Sat, 03 Oct 2020 20:35:07 GMT

@ZhangJennie your answer is helpful. I want to carve out a section of RAM with a NO_INIT qualifier for improved start up time.

How do I assign a variable to this particular segment?

Re: How to set a NO-INIT var in C startup runtime?

mihir_rajput — Sun, 04 Oct 2020 23:45:32 GMT

In a c file:

#pragma DATA_SEG restart_detection_ram_data
static RestartStruct_t restart;
#pragma DATA_SEG DEFAULT

In prm file:

SEGMENTS

/* RAM 8k */
STARTUP_RAM = NO_INIT 0x001000 TO 0x00103F; // 64 bytes

RAM = READ_WRITE 0x001040 TO 0x002DFF; // 8k - 64 - 512 bytes

PLACEMENT

SSTACK, /* allocate stack first to avoid overwriting variables on overflow */
DEFAULT_RAM INTO RAM;
restart_detection_ram_data INTO STARTUP_RAM;