8-bit MicrocontrollersのトピックRe: problem in declaring variables and pointer at absolute address

problem in declaring variables and pointer at absolute address

gauri_mahajan — Thu, 15 Jun 2006 12:37:16 GMT

I am working on 68HC11E9 processor and writing code in C for IAR embedded workbench compiler . I need to declare variables and pointer at absolute addresses in npage area (at 0x170). This IAR compiler doesn't support "@" operator and also it doesn't support "#pragma location = " declaration.

I have tried one more option to create a seperate data segment in RAM and then do it. But that also doesn't work.

Can anybody help me in how to do this?

Thanks and regards,

Gauri

Re: problem in declaring variables and pointer at absolute address

CrasyCat — Thu, 15 Jun 2006 13:38:09 GMT

Hello

I am not familiar with IAR front-end. However defining your variable as follows is fully ANSI C compliant, so IAR compiler should support that too:

#define data (*((char *) 0x0170))

You can then initialize this variable in following way:

data = 8;

CrasyCat

Re: problem in declaring variables and pointer at absolute address

gauri_mahajan — Thu, 15 Jun 2006 14:12:31 GMT

This way I am able to declare variable , but unable to use it in program. there compiler gives error. Also I wish to have pointer located at a specific memory location. This way , it is not possible.

Re: problem in declaring variables and pointer at absolute address

Sten — Thu, 15 Jun 2006 14:23:26 GMT

The way CrazyCat described is what IAR themselves use (see IO6811.H for example), and it works fully in my programs.

What error do you get?

Re: problem in declaring variables and pointer at absolute address

gauri_mahajan — Thu, 15 Jun 2006 15:22:10 GMT

I get an error "Argument of binary operator missing" at the line "data = 8".

If I comment the line "data = 8", the program compiles without error for #define statement.

Re: problem in declaring variables and pointer at absolute address

Sten — Thu, 15 Jun 2006 16:34:38 GMT

I just tested the CrazyCat's lines in one of my project, and they compile without errors. I am using "Micro Series 68HC11 C-Compiler V3.31C/DXT".

Are you sure you haven't added a semicolon to the #define-line?

Re: problem in declaring variables and pointer at absolute address

gauri_mahajan — Thu, 15 Jun 2006 17:58:06 GMT

yes, you are right. I have given semicolon at the end. So I was getting the error. So I could place a variable at a perticular location. Thanks.

But I also need to place a pointer at specific location. Can you please help me....

Re: problem in declaring variables and pointer at absolute address

Sten — Thu, 15 Jun 2006 18:27:11 GMT

I do not understand why you would need a pointer to be in a specific position (and not point to a specific position), but here is a way to do it:

#define data (*((char *) 0x170))    // define a variable at address 0x170
#define pdata (*((char **)0x172)) // define a pointer to a char at address 0x172

  data = 8; // the char at 0x170 will be set to 8
  pdata = (char *) 0x170; // the pointer at 0x172 will be set to 0x170
  *pdata = 8; // the char pointed to by 0x172 is set to 8 (same as data = 8)

Re: problem in declaring variables and pointer at absolute address

gauri_mahajan — Fri, 16 Jun 2006 15:23:09 GMT

Thank you Sten! It solved my problem.

The requirement was for a function to check RAM. This function's variables also reside in the same RAM. So these variables need to be at specific addresses.

Thank you all who helped me.

Regards,

Gauri