TM4C129ENCPDT: Flash Memory Protection Policy Combinations

Amir-Yungman

Part Number: TM4C129ENCPDT

"If a bit is set in this register, the corresponding block may be executed or read by software or debuggers. If a bits in this register are cleared and the same block in the FMPREn register is cleared, the corresponding block may only be executed, and contents of the memory block are prohibited from being read as data."

What exactly do you mean software?

When I am using the combination (FMPPEn=0, FMPREn=0) or (FMPPE=1, FMPRE=0) the read access is not allowed.

So my question is, if I have inside the FLASH const values or tables, will my firmware code running from that FLASH will not be able to read the tables or consts?

Or by software you are refering to external softwares?

over 8 years ago

0 Bob Crosby over 8 years ago

TI__Guru 72500 points

Your firmware executing from flash will not be able to read literals, constants or tables in a read protected sector. There is further explanation in section 8.2.3.5 of the datasheet.

The TI ARM C-compiler supports not embedding literals in the .text section with the following option. it does have a small negative impact on code efficiency.

0 Amir-Yungman over 8 years ago in reply to Bob Crosby

Intellectual 410 points

Thanks a lot, I will read it thoroughly,

How about this mode: (FMPPE=1, FMPRE=0) - The block may be written, erased or executed, but not read. This combination is unlikely to
be used.

There is NO explanation on the datasheet.

1. That interesting mode allow executed, so, will it NOW allow the code to READ constants and literals placed inside .text?

2. Why do you say "This combination is unlikely to be used" - it sounds like that's the most relevant mode ... :-) ... what do I miss?

0 Bob Crosby over 8 years ago in reply to Amir-Yungman

TI__Guru 72500 points

1. No, if the block may not be read, then the code cannot read constants or literals in that block.
2. Usually code that is protected from "Read" is also write protected.

0 Amir-Yungman over 8 years ago in reply to Bob Crosby

Intellectual 410 points

Tx a lot.

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TM4C129ENCPDT: Flash Memory Protection Policy Combinations