TMS320F280039C: How to define a constant for embedded assembly in C?

Wayne Huang

Genius 17205 points

Part Number: TMS320F280039C

Dear Champs,

I am asking this for our customers.

The user can use below codes for bootloader-like code in C to jump to and back from an address.

asm(" MOVL XAR7,#0x81000");

asm(" LCR *XAR7");

They want to change #0x81000 to a defined constant address in the beginning of the C file so that they can just maintain the address like

#define address 0x81000

.....

asm(" MOVL XAR7, address");

asm(" LCR *XAR7");

Is it possible to do so in a similar way using C code or embedded assembly in the beginning of the same C code?

over 2 years ago

0 Omer Amir over 2 years ago

TI__Mastermind 30185 points

Hello Wayne,

Wayne Huang said:
Is it possible to do so in a similar way using C code or embedded assembly in the beginning of the same C code?

I believe the following thread should help answer this question: https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/194408/how-to-use-global-variable-in-assembly-function.

If the customer is specifically trying to use a #define for a single instruction (such as jumping to an address from only one place in the program), this may not be useful since it's essentially just acting as a label.

Best regards,

Omer Amir

0 Wayne Huang over 2 years ago in reply to Omer Amir

TI__Genius 17205 points

Dear Omer,

I am still confused.

How is the ARM assembly in the post your showed related to this C28x assembly?

Would you please make it clearer or illustrate a simple example?

+1 Omer Amir over 2 years ago in reply to Wayne Huang

TI__Mastermind 30185 points

Apologies, I didn't recognize the difference in the assembly, I was more just reading the explanations.

For C28x assembly you will be using the labels as pointers, see the below example I created (builds without errors):

asm("address .set 0x81000");

void main(void)
{
    asm("    MOVL XAR7, #address");
    asm("    LCR *XAR7");
    while(1);
}

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TMS320F280039C: How to define a constant for embedded assembly in C?