TMS320F2800137: Get data of the address

Hello,

The expert on this topic is currently out of office until Tuesday 9/3, so please expect a delayed response. I apologize for any inconvenience.

Best Regards,
Delaney

hi

Looking forward to your reply.

in other mcu,0x33332222 is right data.but in this mcu data is different.why?
It would be best if you could explain the principle

Hello,

I will try to get to this inquiry this week, but will likely have a few days delay in response. I appreciate your patience in the meantime.

Best Regards,

Allison

hi

Looking forward to your reply.

Is there any progress?

Hello,

Allison is currently out of office but will get back to you with a response as soon as she can. I apologize for any inconvenience.

Best Regards,

Delaney

Hello,

Apologies for the extended delay. Have you already checked the data in CCS when connected to the device? If you go to view > memory browser, and enter the address location you should be able to see what is stored at that location.

Little endian alignment stores LSB at the smallest address, so 0x735 is LSB, then 0x736, etc. When you say that this MCU data is different, what are you seeing as the data? 

Allison

hello

If you go to view > memory browser, and enter the address location you should be able to see what is stored at that location.

yes,the data location is right.

but when i used the pointer to get some data of assigned address,It's not the result I imagined。

as follow.

lTemp = 0x735;//adresss

lAddrData = (*(uint32_t*)(lTemp));//get the data of started address

he value 0f 0x734 is 0x1111;

the value 0f 0x735 is 0x2222;

the value 0f 0x736 is 0x3333;

When you say that this MCU data is different, what are you seeing as the data? 

i used the same code,and show the result of lAddrData .

in other mcu, the lAddrData  =  0x33332222;It is to forward 32-bit data according to the specified address

but in c2000,the lAddrData  =  0x22221111;It is data that goes 32 bits forward according to even addresses

you can test in c2000.

i want to kown why?and how to deal as the other mcu?

Hello,

The appropriate expert for this question is currently out of office, returning on Monday 9/16. Please expect a response back by then.

Thank you,

Luke

hi

Looking forward to your reply.

Is there any progress?

hi

Can you solve this problem as soon as possible? It's been 21 days now.

Is there only one expert who can answer this question?

Hi Youjun,

My sincere apologies for the extended delay from being out.

I believe this may be a product of our compiler - I am looping in another expert for input on this.

Best Regards,

Allison

Hi Youjun,

Please refer to the Instruction set manual (linked here) section 5.11 Alignment of 32-Bit Operations for an explanation of what happens with a 32-bit read of data from an odd address boundary.

On the c28x when you do a 32-bit read of the data starting at address lTemp, this is attempting to read on an odd boundary. The section states that the high order bits are taken from the next highest 16-bit address increment in little endian format. The next highest address from 0x735 is 0x734 (higher up in memory- not numerically), so 0x1111 is grabbed. Since it is in little endian, the 0x2222 and 0x1111 are swapped, putting 0x2222 in the most significant bytes.

youjun zhang said:

nd how to deal as the other mcu?

What exactly are you trying to do with the MCU? Are you just converting your code over to c28x architecture? 

Best Regards,

Delaney

hi Delaney

What exactly are you trying to do with the MCU? 

i want to read some information (saved in some variables),such as data[8](16bit),i need read 4 datas(64bit) from data[1],not from data[0];

When used, if not careful, errors can occur and it is difficult to find the cause.

Is there a way to change this Instruction setting or avoid this?

Hi Youjun,

I believe the best way to avoid any errors here would be to place and read data only from the even address boundaries. I'm still not sure I understand the use case, is there a reason you need to read from an address in memory directly rather than reading from a variable or register? If you are reading from a variable, you shouldn't see this alignment issue because the compiler would place it on an even address boundary automatically (to my knowledge).

Best Regards,

Delaney

hi

i uese a Freemaster software,the Freemaster only send an address and the length,so i need to read from an address in memory directly.

Is there a way to change this Instruction setting?

Hi Youjun,

Are using the Freemaster software for debugging purposes? I would suggest using the CCS software instead since this will always be compatible with the c28x CPU. Let me know if this is feasible.

Best Regards,

Delaney

hi

this is only a example.

some case,i maybe need to read from an address in memory directly.

Is there a way to change this Instruction setting?

hello

This is very difficult for me, can professionals  try ?

Hi Youjun,

Unfortunately, that is beyond the scope of what we can provide on E2E. You are always free to manipulate the data after it's read in some way (for example reading in two uint32_t values and bit shifting to create a variable with the value you expect). I will loop in another expert to see if they have any comments, but as far as I know there isn't an easy way to get around this. 

Best Regards,

Delaney