S12 / MagniV MicrocontrollersのトピックRe: Copy Values from ROM to RAM at startup

Copy Values from ROM to RAM at startup

Donal — Mon, 18 Dec 2006 18:32:55 GMT

Hello All,
I have a problem where I need to copy calibrations from ROM to RAM upon startup, but I wish to keep the same variable name throughout the application code.

For example, a calibration variable initialization is as follows:

#pragma CONST_SEG EEPROM_CALS
extern const U32 Sb10_Constant8 = 0x0023;

Now, this variable is used throughout the application. And there are certain situations when I will want to modify this value, to test the behaviour of the application to this new value. I may also want to flash this new value back into EEPROM.

There can't be a second RAM variable for this, as part of the application is auto generated.
So the following simple solution would not suffice:
Sb10_Constant8_RAM = Sb10_Constant8_ROM;

Is there any method to allow the variable initialization to occur but upon start-up the value is copied into RAM with the variable name Sb10_Constant8 always residing in RAM?

Cheers,
Donal

Re: Copy Values from ROM to RAM at startup

bigmac — Mon, 18 Dec 2006 18:55:08 GMT

Hello Donal,

I do not quite understand why the variables at the two different locations cannot have different names. I assume that the RAM locations could be global variables, and explicitly assigned an initial value corresponding to the required constant value.

Or have I missed something obvious?

Regards,

Mac

Re: Copy Values from ROM to RAM at startup

CrasyCat — Mon, 18 Dec 2006 19:47:47 GMT

Hello

I assume you are using CodeWarrior for HC08 or HC12 as development software. Am I right?

If this is the case, the standard Startup code we are delivering is copying initialization value from ROM to RAM at startup. Just make sure you are using ANSI C startup and not minimal startup code when creating your application.

If you have already created your project, make sure to remove the option -D__ONLY_INIT_SP from the compiler command line and rebuild your application.

CrasyCat

Re: Copy Values from ROM to RAM at startup

Donal — Mon, 18 Dec 2006 19:51:18 GMT

Hi Mac : The names of the calibration variables are global, but we can't change them as they are autogenerated along with a large proportion of the code. If we were to have different names then it would involve a lot or rework each time the autogenerated code is updated.

CrasyCat: I am using Codewarrior for the HCS12. So I have to modify this startup code so that it will copy my calibrations from ROM to RAM. Will the varibale names also point to the RAM copies rather than ROM?

Cheers,
Donal

Re: Copy Values from ROM to RAM at startup

Lundin — Mon, 18 Dec 2006 22:56:37 GMT

What you wish to do is to allocate a variable at two locations. That isn't possible, since it doesn't make sense. But if you must, you could simulate that behaviour with macros. Lets assume that MY_VAR is the holy name that you use all over the code which cannot be changed:

#define MY_VAR (*address)

#pragma CONST_SEG GLOBAL_ROM
const volatile int myVarROM = something;

#pragma DATA_SEG GLOBAL_RAM
volatile int myVarRAM = myVarROM;

volatile int* address = &myVarROM

...

int main()
{
...
myVarRAM = changedToSomething;
address = &myVarRAM;