topic Re: Calculating a CRC32 for program code over multiple pages via prm instructions in CodeWarrior for MCU

Calculating a CRC32 for program code over multiple pages via prm instructions

Stephen — Tue, 31 Jul 2007 07:36:18 GMT

I have an application whose program code spans several 16k pages of Banked ROM.

I am trying to use the prm CHECKSUM instruction to calculate a CRC32 value for the program code, however I cannot find the right syntax for the CHECKSUM block to do this.

I have tried the following:

CHECKSUM
    CHECKSUM_ENTRY
        METHOD_CRC32
        OF      READ_ONLY   0x4004 TO 0x7FFF, 0xC000 TO 0xFFFF
        INTO    READ_ONLY   0x4000 SIZE 4
        UNDEFINED 0xFF
    END
END

and

CHECKSUM
    CHECKSUM_ENTRY
        METHOD_CRC32
        OF      READ_ONLY   0x4004 TO 0x7FFF
        OF      READ_ONLY   0xC000 TO 0xFFFF
        INTO    READ_ONLY   0x4000 SIZE 4
        UNDEFINED 0xFF
    END
END
Both generate error message from the linker

I am currently Code Warrior running version 4.5

Any suggestion please?

Steve

Re: Calculating a CRC32 for program code over multiple pages via prm instructions

CrasyCat — Tue, 31 Jul 2007 13:39:21 GMT

Hello

You cannot compute a checksum across page boundary.

You need to define a CHECKSUM_ENTRY block for each page you are using in your PRM file.

Checksum calculation cannot be performed on non-contiguous memory area.

Also you cannot have several memory areas specified in a CHECKSUM_ENTRY block.

CrasyCat

Re: Calculating a CRC32 for program code over multiple pages via prm instructions

Stephen — Fri, 03 Aug 2007 07:44:50 GMT

Thanks very much for your answer - not what I was hoping for but there you go. Is there any chance that Metrowerks will extend the checksum functionality in the future?

Steve

Re: Calculating a CRC32 for program code over multiple pages via prm instructions

CrasyCat — Fri, 03 Aug 2007 12:46:57 GMT

Hello

That would be a feature request (or a change request).

I would recommend you to submit a service request for that through our web interface to ask for this extension.

Click here to submit a service request.

CrasyCat

Re: Calculating a CRC32 for program code over multiple pages via prm instructions

CompilerGuru — Fri, 03 Aug 2007 18:09:10 GMT

What's the gain of having a single checksum for two areas compared to 2 checksums for two separate areas?
In the end the code computing the checksum at runtime has to know the boundaries of the two areas explicitely anyway. I doubt that the single checksum area uses less flash as it explicitely has to combine the two checksum while the 2 checksum version can just reuse the same code twice.

It's a different story when we have 10 pages with the same range in each page, then a combined checksum would help a bit, but I doubt much.
Daniel

Re: Calculating a CRC32 for program code over multiple pages via prm instructions

Stephen — Tue, 14 Aug 2007 07:59:55 GMT

Simple - the reason is that the customer specification asks that we give a single CRC32 checksum for the complete code.