TMS320F28379D: Questions about the assembly code "MOV"

Yu Qi1

Hi, I have a question about the assembly code on TMS320F28379D. I added my code on the example project names "blinky_cpu01".

And the main file's code is shown below

#include "F28x_Project.h"
extern void test_MOV();
uint32_t test_num = 1;
void main(void)
{
    InitSysCtrl();
    InitGpio();
    GPIO_SetupPinMux(31, GPIO_MUX_CPU1, 0);
    GPIO_SetupPinOptions(31, GPIO_OUTPUT, GPIO_PUSHPULL);
    DINT;

    InitPieCtrl();
    IER = 0x0000;
    IFR = 0x0000;
    InitPieVectTable();
    EINT;  // Enable Global interrupt INTM
    ERTM;  // Enable Global realtime interrupt DBGM
    test_MOV();
    for(;;)
    {
        GPIO_WritePin(31, 0);
        DELAY_US(1000*500);
        GPIO_WritePin(31, 1);
        DELAY_US(1000*500);
    }
}

The "test_MOV()" is defined in another asm file and the code is

	.ref _test_num
	.def _test_MOV

_test_MOV:
    MOV     AR0, #_test_num
    MOV     AL, *AR0
    MOV     AR1, AL
	LRETR

The function of code should be moving test_num, which is 1 by initialization, into AR1.

However, After running this, AR1 is 0, which is not as expected. Could you please give me some suggestion about this problem? Thank you

over 3 years ago

0 Santosh Jha over 3 years ago

TI__Guru 50611 points

Hi,

I just tried on my setup and it seems to work fine.

Can you open the disassembly window and then assembly step through the code and see where it fails?

Thanks & Regards,

Santosh

0 Yu Qi1 over 3 years ago in reply to Santosh Jha

Prodigy 100 points

This is the process of the code running. It seems to fail at "MOV AL, *AR0"

0 Santosh Jha over 3 years ago in reply to Yu Qi1

TI__Guru 50611 points

Hi,

Can you just try this?

_test_MOV:

MOV AR1, *(_test_num)

LRETR

MOVZ DP, #_test_num

MOVZ AR1, @_test_num

LRETR

0 Yu Qi1 over 3 years ago in reply to Santosh Jha

Prodigy 100 points

Thanks for your timely reply. But instead of changing the code, I still wonder why my code not working.

0 Santosh Jha over 3 years ago in reply to Yu Qi1

TI__Guru 50611 points

Hi,

I have asked compiler and assembly expert to take a look. Please expect response later today or tomorrow.

Just wondering, if you tried the work-arounds and can you confirm if they work for you?

Thanks & Regards,

Santosh

+1 Santosh Jha over 3 years ago in reply to Santosh Jha

TI__Guru 50611 points

Hi,

Please take a look in the disassembly window has the answer.

0080e5: 92C0 MOV AL, *+XAR0[0]

The _X_ on XAR0 means the whole register is being used as a pointer. So there is some data in the high half of the XAR0 register (AR0H) and thus XAR0 points somewhere other than the intended location. Looking in the instruction set guide (SPRU430) there isn’t a *ARx form of the instruction.

So if you initialize the XAR0 with 0, then your code should work fine.

    MOVL    XAR0, #0x00
    MOV     AR0, #_test_num
    MOVW    AL, *AR0
    MOV     AR1, AL

Thanks & Regards,

Santosh

0 Yu Qi1 over 3 years ago in reply to Santosh Jha

Prodigy 100 points

Thank you for your clear and nice explanation. It's really helpful and fixed my problem.

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TMS320F28379D: Questions about the assembly code "MOV"