MSP430FR2355: MPU and .persistent on MSP430FR2355

Dzmitry Stsepankou

Prodigy 25 points

Part Number: MSP430FR2355

Tool/software:

Hi,

I'm working with FR2355 and using the #pragma PERSISTENT variables.

Everything worked fine with the default linker file.

After I modified the FRAM allocation:

instead of the deafult:

FRAM : origin = 0x8000, length = 0x7F80

I changed to:

FRAM : origin = 0x8002, length = 0x7F7E

the PERSISTENT variable is not writable any more.

In the map-file the variable is still correctly maped to the persistant block!

As far as I understood this is because of the memory segments, that are 1024bytes aligned.

I noticed in the map-file once I changed the start address of the FRAM, the persistant block is being shifted to the 0x8400 address by the linker.

So, my next thought was to implement the custom MPU configuration as in slaa628 (6.3.1.1.1).

This doesn't work however, because the registers like: MPUCTL0 are not defined (I'm using CCS12.7).

I also don't see the MPU wizard in my CCS as it's shown on Fig 6-4 (slaa628), I only see one option "Enable FRAM Write protection", nothing like segments.

Is this document outdated? Or is the MPU not supported for the FR2355 device?

What could be a solution to this problem?

Kind Regards,

Dzmitry

8 days ago

0 David Schultz 8 days ago

Guru 19645 points

Some devices, such as the fr2355, do not have an MPU. Just a write protect flag.

This is discussed in slaa628.

0 Dzmitry Stsepankou 7 days ago in reply to David Schultz

Prodigy 25 points

Thanks for the reply, David!

I'm kind of realized that already, but why the PERSISTENT is write protected after the default FRAM map is changed is still a puzzle ....

0 David Schultz 7 days ago in reply to Dzmitry Stsepankou

Guru 19645 points

Check out the documentation on FRWPOA. This carves out some of the program FRAM space from write protection. With 1K resolution.

0 Sal Ye 4 days ago in reply to Dzmitry Stsepankou

TI__Genius 11135 points

Hi Dzmitry,

https://e2e.ti.com/support/microcontrollers/msp-low-power-microcontrollers-group/msp430/f/msp-low-power-microcontroller-forum/616911/ccs-msp430fr2033-cannot-write-to-fram-variable-placed-with-pragma-data_section-to-custom-fram-memory-section

I think this thread could solve the puzzle.

B.R.

Sal

0 Dzmitry Stsepankou 2 days ago in reply to David Schultz

Prodigy 25 points

Thanks David, controlling the FRWPOA manually resolved the issue.

0 Dzmitry Stsepankou 2 days ago in reply to Sal Ye

Prodigy 25 points

Thanks for the answer, however there's a slight difference between this case and mine.

As I mentioned, with the default makefile configuration I was able to write without issues.

As David mentioned there is a register that controls the FRAM protection.

So by default, as this seems to me, it's controlled by some values chosen by the CCS/linker(?) (that are unkown and undocumented).

I believe the only solution is to manually control the FRWPOA values, which indid resolved the issue.

0 Sal Ye 2 days ago in reply to Dzmitry Stsepankou

TI__Genius 11135 points

Hi Dzmitry,

Thanks your feedback here. That's correct.

There is difference between FR235x and FR2033 device. The document (https://www.ti.com/lit/an/slaa628b/slaa628b.pdf) shows below:

For FR2xx FR4xx series MCUs, except for the FR235x and FR215x devices, can operate the PFWP and DFWP register to enable or disable the write protection for main memory and the Information Memory in the FRAM. After a PUC reset, those bit defaults to 1, and writes to FRAM are disabled. User code must write the correct password and clear the corresponding bit before write operation.

I missed the difference.

B.R.

Sal

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MSP430FR2355: MPU and .persistent on MSP430FR2355