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Large Lookup Table -- Can't Store in ROM?

Tim Payne

Hi,

I'm wondering if I am doing something wrong here. I am trying to store an array for a large 256 byte look-up table.

I have a pretty small 8051 MCU of 8 KB flash memory (IROM), 256 bytes internal RAM (IRAM) and 256 bytes on-chip external RAM (XRAM).

Prior to adding this look-up table, my current build from Keil reports:

"Program Size: data=54.1 xdata=0 code=1984"

I take that to mean I am using 54 bytes of IRAM, 0 bytes of XRAM, and 1984 bytes of IROM?

Here is the variable declaration I am using:

code unsigned char CRC8LookupTable[256];

When I define the CRC8LookupTable and populate values, I get the Segment Too Large error.

If you use "code" doesn't that store the values in ROM, which I should have plenty of space for?

Is there something else I need to add to that variable declaration?

Thanks
-Tim

Parents Reply Children
  • 0 in reply to Andy Neil

    YOU'VE NOW FINALLY READ ABOUT THEM MR NEIL? SEE EXTERN IS ***NOT*** NEEDED. WELL DONE.

  • 0 in reply to Andy Neil

    @Andrew

    You are correct, I mistyped all that. Tenative definitions -- that are in my header declarations (there is a mouthful).

    What a language C is. I have a brother who was a decent web programmer, and now is a very good securities lawyer. Frigging exact same thing, very technical language with exacting logic. Except securities contracts are written in English vs. C.

    I miss the good old days of PHP & Python -- now that is an easy language compared to C.

    I appreciate the help. Seriously.

  • 0 in reply to Tim Payne

    I TREAT C AS A TOOL. I THINK I KNOW ENOUGH TO GET THE JOB DONE BUT SURE OF COURSE SOME PEOPLE WILL ARGUE I DON'T KNOW ENOUGH.

    IT IS GOOD TO KEEP GOOD MANUALS TO HAND TO CHECK THINGS RARELY USED OR EASILY FORGOTTEN.

    ALWAYS GOOD TO LEARN FROM OTHERS AND ACKNOWLEDGE ***GOOD*** ADVICE.

    C IS NO MORE DIFFICULT THAN MANY OTHER LANGUAGES. JUST LIKE OTHERS, PRACTICE IS IMPORTANT.